Records 1 - 20 / 736
Green Challenges: Bestrijding van Meloidogyne spp. (wortelknobbelaaltjes) in chrysant metbiologische bestrijdingsmiddelen en biostimulanten
Long, Jonathan R. De; Streminska, Marta ; Persijn, Ariyati ; Huisman, Ming ; Salm, Caroline van der - \ 2020
Bleiswijk : Stichting Wageningen Research, Wageningen Plant Research, Business unit Glastuinbouw (Rapport WPR 944) - 29
Root-knot nematodes (Meloidogyne spp.) are a worldwide problem in many crops. These nematodes are a particular problem in glasshouse-grown chrysanthemums. In order to combat root-knot nematodes in the glasshouse, the soil is typically steamed every 5-6 growth cycles. However, this method is expensive, environmentally unfriendly and reduces the resistance and resilience of the soil against other pathogens and pests. In this experiment we added different biological pesticides and basic substances and biostimulants both individually and in combination in order to determine if there is an interactive or additive effect against damage caused by root-knot nematodes in chrysanthemums. We found that the use of the biological pesticide derived from garlic extract and the basic substance chitosan HCl and biostimulants comprised of sea minerals and plant oils reduced the damage to chrysanthemum caused by root-knot nematodes. A number of the treatments caused a reduction in plant biomass (e.g., soldier fly waste products and their interaction with chitosan HCl and interactions between the chemical nematicide oxamyl and several of the biostimulants). However, this reduction was minimal.
Green Challenges: plant en bodemweerbaarheidtegen ondergrondse ziekten
Streminska, Marta ; Breeuwsma, Suzanne ; Huisman, Huei Ming ; Vos, Ric de; Eekelen, Henriette van; Stevens, Luc ; Salm, Caroline van der - \ 2020
Bleiswijk : Stichting Wageningen Research, Wageningen Plant Research, Business unit Glastuinbouw (Rapport WPR 943) - 61
Crops in soil-based and soilless greenhouse cultivation systems are susceptible to various soilborne diseases, such as foot and root rot and wilting, caused by pathogens as Fusarium and Pythium. The Grºeen Challenges project aims to reduce the use of chemical plant protection products and to develop new measures and strategies for disease and pest control through a system approach. This project investigated which measures can be taken to promote soil disease suppression and induced plant resistance against soilborne pathogens (Fusarium and Pythium) in different horticultural crops: vegetable crops (tomato and cucumber) and ornamental crop (lisianthus).
A roadmap towards engineered nitrogen-fixing nodule symbiosis
Huisman, R.H.J. ; Geurts, R. - \ 2020
Plant Communications 1 (2020)1. - ISSN 2590-3462 - 16 p.
In the late 19th century, it was discovered that legumes can establish a root nodule endosymbiosis with nitrogen-fixing rhizobia. Soon after, the question was raised whether it is possible to transfer this trait to non-leguminous crops. In the past century, an ever-increasing amount of knowledge provided unique insights into the cellular, molecular, and genetic processes controlling this endosymbiosis. In addition, recent phylogenomic studies uncovered several genes that evolved to function specifically to control nodule formation and bacterial infection. However, despite this massive body of knowledge, the long-standing objective to engineer the nitrogen-fixing nodulation trait on non-leguminous crop plants has not been achieved yet. In this review, the unsolved questions and engineering strategies toward nitrogen-fixing nodulation in non-legume plants are discussed and highlighted.
SNARE Complexity in Arbuscular Mycorrhizal Symbiosis
Huisman, Rik ; Hontelez, Jan ; Bisseling, Ton ; Limpens, Erik - \ 2020
Frontiers in Plant Science 11 (2020). - ISSN 1664-462X
arbuscular mycorrhiza - exocytosis - Medicago - membrane - SNARE - symbiosis - syntaxin - VAMP
How cells control the proper delivery of vesicles and their associated cargo to specific plasma membrane (PM) domains upon internal or external cues is a major question in plant cell biology. A widely held hypothesis is that expansion of plant exocytotic machinery components, such as SNARE proteins, has led to a diversification of exocytotic membrane trafficking pathways to function in specific biological processes. A key biological process that involves the creation of a specialized PM domain is the formation of a host–microbe interface (the peri-arbuscular membrane) in the symbiosis with arbuscular mycorrhizal fungi. We have previously shown that the ability to intracellularly host AM fungi correlates with the evolutionary expansion of both v- (VAMP721d/e) and t-SNARE (SYP132α) proteins, that are essential for arbuscule formation in Medicago truncatula. Here we studied to what extent the symbiotic SNAREs are different from their non-symbiotic family members and whether symbiotic SNAREs define a distinct symbiotic membrane trafficking pathway. We show that all tested SYP1 family proteins, and most of the non-symbiotic VAMP72 members, are able to complement the defect in arbuscule formation upon knock-down/-out of their symbiotic counterparts when expressed at sufficient levels. This functional redundancy is in line with the ability of all tested v- and t-SNARE combinations to form SNARE complexes. Interestingly, the symbiotic t-SNARE SYP132α appeared to occur less in complex with v-SNAREs compared to the non-symbiotic syntaxins in arbuscule-containing cells. This correlated with a preferential localization of SYP132α to functional branches of partially collapsing arbuscules, while non-symbiotic syntaxins accumulate at the degrading parts. Overexpression of VAMP721e caused a shift in SYP132α localization toward the degrading parts, suggesting an influence on its endocytic turn-over. These data indicate that the symbiotic SNAREs do not selectively interact to define a symbiotic vesicle trafficking pathway, but that symbiotic SNARE complexes are more rapidly disassembled resulting in a preferential localization of SYP132α at functional arbuscule branches.
The Chinese milk supply chain: A fraud perspective
Yang, Yuzheng ; Huisman, Wim ; Hettinga, Kasper A. ; Zhang, Liebing ; Ruth, Saskia M. van - \ 2020
Food Control 113 (2020). - ISSN 0956-7135
China - Dairy farmer - Economically motivated adulteration - Fraud vulnerability assessment - Milk processor - Milk supply chain
Food fraud has become a serious concern all over the world and especially in China. The melamine contaminated infant formula in 2008 has brought food fraud in the spotlights. This incident had grave consequences for the Chinese citizens as well as the Chinese milk industry. Fraud vulnerability assessments are the first step towards food fraud prevention and mitigation. To combat food fraud, one has to think like a criminal. In the current study, we determined the most vulnerable points in the Chinese milk supply chain, and examined the underlying causes. The fraud vulnerability perceived by 90 Chinese dairy farmers and 14 milk processors was evaluated with the SSAFE food fraud vulnerability assessment tool. Overall, actors perceived the milk supply chain as low to medium vulnerable to food fraud. Farmers appeared significantly more vulnerable than processors due to enhanced opportunities and motivations, and less adequate controls. Both geographical location of the farms and their size affected their perceived fraud vulnerability significantly.
Feeding fiction: Fraud vulnerability in the food service industry
Ruth, Saskia M. van; Veeken, Joris van der; Dekker, Pieter ; Luning, Pieternel A. ; Huisman, Wim - \ 2020
Food Research International 133 (2020). - ISSN 0963-9969
Dining - Food fraud - Fraud prevention - Hospitality - Integrity - Mass caterer - Restaurant
This study examines fraud vulnerability in the food service industry; identifies underlying fraud vulnerability factors; and studies the differences in fraud vulnerability between casual dining restaurants, fine dining restaurants and mass caterers for four product groups. Vulnerability was assessed by an adapted SSAFE food fraud vulnerability assessment, tailored to the food service sector situation. The 15 food service operators rated high vulnerability for 40% of the fraud indicators. This is considerably more than food manufacturers, wholesalers and retailers did previously. In particular, more opportunities and fewer controls were noted. Overall fraud vulnerability was more determined by the type of food service operator than by the type of food product. Casual dining restaurants appeared most vulnerable, followed by fine dining restaurants. Mass caterers seemed the least vulnerable operators, because they had more adequate food fraud controls in place. Considering its high vulnerability, reinforcement of mitigation measures in the food service industry is urgently recommended.
A context analysis on how oral care is delivered in hospitalised patients: A mixed-methods study
Noort, Harm H.J. van; Witteman, Ben J.M. ; Hertog-Voortman, Ria den; Everaars, Babette ; Vermeulen, Hester ; Huisman-de Waal, Getty - \ 2020
Journal of Clinical Nursing 29 (2020)11-12. - ISSN 0962-1067 - p. 1991 - 2003.
fundamental care - hospitalised patients - interviews - mixed methods - nondental care professional - nursing - oral care - oral health - oral health assessment tool - oral hygiene
Aims and Objectives: To analyse oral care delivery in one hospital through exploring experiences from both nurses’ and patients’ perspectives and examining patients’ oral health. Background: Oral health problems are associated with undernutrition and other general health outcomes. Although oral care belongs to the essentials of nursing, it is often neglected. Improving oral health may require behaviour change of both nurses and patients. Defining tailored strategies need a clear view on the context. Design: A context analysis in one hospital using a convergent parallel mixed-methods design was reported following the EQUATOR guidelines using two checklists: COnsolidated criteria for REporting Qualitative research (qualitative research) and STROBE (observational research). Methods: Semi-structured interviews were conducted with 19 nurses and 11 patients. The topic list was based on the Integrated Change Model. Prospective oral examination was performed among 91 surgical patients using the Oral Health Assessment Tool (OHAT). Results: Nurses acknowledged that they did not prioritise oral care in daily practice. Furthermore, they lacked knowledge and skills to identify and provide care for oral problems. Nurses mentioned helpful resources to perform oral care, like standardised language and instruments. However, they had no access to or were unaware of them. Patients admitted that they did not prioritise oral care due to their sickness during hospitalisation, were unaware of the importance of oral care, but felt responsible for their oral care. The most prominent oral problems identified with the OHAT were unclean mouths (n = 75, 82%), unhealthy gum and tissues (n = 55, 60%) and dry mouth (n = 42, 46%). Conclusions: This context analysis identified inadequate oral care due to lack of positive attitude and knowledge in both nurses and patients, skills for nurses, and resources. Relevance to Clinical Practice: The behavioural factors indicate strategies for development of a multicomponent intervention to improve oral care in this hospital, nutritional status and general health outcomes.
Building an Artificial Stem Cell Niche: Prerequisites for Future 3D-Formation of Inner Ear Structures—Toward 3D Inner Ear Biotechnology
Groot, Simon C. de; Sliedregt, Karen ; Benthem, Peter Paul G. van; Rivolta, Marcelo N. ; Huisman, Margriet A. - \ 2020
The Anatomical Record 303 (2020)3. - ISSN 1932-8486 - p. 408 - 426.
3D - biotechnology - inner ear - stem cell
In recent years, there has been an increased interest in stem cells for the purpose of regenerative medicine to deliver a wide range of therapies to treat many diseases. However, two-dimensional cultures of stem cells are of limited use when studying the mechanism of pathogenesis of diseases and the feasibility of a treatment. Therefore, research is focusing on the strengths of stem cells in the three-dimensional (3D) structures mimicking organs, that is, organoids, or organ-on-chip, for modeling human biology and disease. As 3D technology advances, it is necessary to know which signals stem cells need to multiply and differentiate into complex structures. This holds especially true for the complex 3D structure of the inner ear. Recent work suggests that although other factors play a role, the extracellular matrix (ECM), including its topography, is crucial to mimic a stem cell niche in vitro and to drive stem cells toward the formation of the tissue of interest. Technological developments have led to the investigation of biomaterials that closely resemble the native ECM. In the fast forward moving research of organoids and organs-on-chip, the inner ear has hardly received attention. This review aims to provide an overview, by describing the general context in which cells, matrix and morphogens cooperate in order to build a tissue, to facilitate research in 3D inner ear technology. Anat Rec, 2019.
An outpatient nursing nutritional intervention to prehabilitate undernourished patients planned for surgery : A multicentre, cluster-randomised pilot study
Noort, Harm H.J. van; Witteman, Ben J.M. ; Vermeulen, Hester ; Huisman-de Waal, Getty ; Hamers, J.P.H. - \ 2019
Clinical Nutrition 39 (2019)8. - ISSN 0261-5614 - p. 2420 - 2427.
Essential care - Nursing care - Nutritional support - Prehabilitation - Preoperative care - Undernutrition
Background & aims: To improve the nutritional status of surgical patients before hospital admission, an Outpatient Nursing Nutritional Intervention (ONNI) was developed. The ONNI comprehends five components: determining causes of undernutrition, performing a nutritional care plan including tailored and general advice, self-monitoring of nutritional intake and eating patterns, counselling and encouragement, and conducting a follow-up telephone call to discuss improvements in nutritional behaviour. Here, we evaluate the feasibility and effectiveness of the ONNI. Methods: In a multi-centred, cluster-randomised pilot study, nurses from outpatient clinics were randomly allocated to usual care (UC) or the ONNI. Patients planned for elective surgery were included if they were at increased risk for undernutrition based on the Malnutrition Universal Screening Tool (MUST) and hospital admission was not planned within seven days. Feasibility outcomes included participation rate, extent of intervention delivery, and patient satisfaction. Nutritional intake was monitored for two days before admission. Body weight, BMI and MUST scores at hospital admission were compared to measurements from the outpatient clinic visit. Data were analysed on an intention-to-treat basis by researchers who were blinded for patients and caregivers. Results: Forty-eight patients enrolled the feasibility phase. Participation rate was 72%. Nurses delivered all intervention components adequately in the end of the implementation period. Finally, 152 patients (IG: n = 66, 43%) participated in the study. A significant difference in mean energy intake (870 kcal/d, 95%CI:630-1109 p < 0.000) and mean protein intake (34.1 g/d, 95%CI: 25.0–43.2; p < 0.000) was observed in favour of the IG. Nutritional energy requirements were achieved in 74% (n = 46) of the IG and in 17% (n = 13) of the UC group (p < 0.000), and protein requirements were achieved in 52% (n = 32) of the IG, compared to 8% (n = 6) of the UC group (p < 0.000). Body weight, BMI and MUST scores did not change in either group. Conclusions: The ONNI is a feasible and effective intervention tool for nurses at outpatient clinics. Patients in the IG had more nutritional intake and fulfilled nutritional requirements significantly more often than patients receiving UC. Further research is required to determine the optimal pre-operative timing of nutritional support and to measure its effect on other patients groups. Clinical trial registration: The study protocol was registered at the ClinicalTrial.gov website with the following identifier: NCT02440165.
Results and lessons of 17 years of monitoring at the tidal fish pass Roptazijl (The Netherlands)
Huisman, Jeroen - \ 2019
Sluices, weirs and pumping stations form a migratory obstacle for diadromous
fish in estuaries and deltas around the world resulting in decreased recruitment
success and biodiversity of fish fauna in estuarine-riverine systems. In the
Dutch Wadden Sea intertidal fish passes have been built to facilitate
diadromous migration. The fish pass of Roptazijl was built in 2002 and is one
of the first fish passes in the Wadden Sea. The fish pass functions for part of
the tidal cycle. To attract diadromous fish, the fish pass pumps fresh water
over the dyke to a small basin on the Wadden Sea-side. The contents of the
basin, including fish, is siphoned towards the polder every two hours. Passage
of fish has been monitored using a fyke net, every spring, since 2002. In
addition, the presence of diadromous fish on the Wadden Sea-side and
seasonal abundance was monitored in 2014, 2015 and 2016 using cross nets.
Fish pass functioning was logged by the water authority. Results show that the
fish pass is often out of order impairing fish migration. Fyke net monitoring
shows that predominantly sticklebacks and glass eels use the fish pass. Cross
net monitoring on the Wadden Sea-side shows that arrival of stickleback and
glass eels at the fish pass has a relation to the tidal cycle. As such, the
research at Roptazijl, shows that in the design and building of tidal fish passes,
possible temporal window of opportunities for migratory diadromous fish, can be an important design criterion.
|Integrating priorities of disadvantaged parents and professionals for community family health
Wink, G. ; Fransen, G.A.J. ; Huisman, M.J. ; Boersma, S.N. ; Assendelft, Willem J.J. ; Wagemakers, A. ; Velden, J. van der; Muijsenbergh, M.E.T.C. van den - \ 2019
Integrating priorities of disadvantaged parents and professionals for community family health
Wink, G. ; Fransen, G.A.J. ; Huisman, M.J. ; Boersma, S.N. ; Assendelft, W.J.J. ; Wagemakers, M.A.E. ; Velden, J. van der; Muijsenbergh, M.E.T.C. van den - \ 2019
European Journal of Public Health 29 (2019)Supplement_4. - ISSN 1101-1262 - p. 374 - 375.
Health inequalities persist, and policymakers, researchers and practitioners seek for effective ways to positively impact the health of disadvantaged people. Researchers point to a multi-component program with an integral design including various perspectives and involving different stakeholders. Few studies address the perspectives on health of disadvantaged people themselves. This study describes what parents in a socially disadvantaged situation and professionals working in that community perceived as 1) priority aspects to improve family health 2) barriers and facilitators for health behaviour changes 3) important health program activities.
Design: Community-based participatory action research. 10 parents participated in 6 panel meetings. 46 professionals received 4 panel meetings summaries. 18 parents and 25 professionals responded to questions in (panel) meetings and consultation by phone and e-mail.
(preliminary) 1) Parents’ top priorities for improving health were: less stress related to finances and communication with related organizations, followed by a safe place for kids to meet. Of the program financers’ aims (reducing tobacco, alcohol use and overweight) reducing overweight got relatively most support of parents. 2) Parents perceived their family financial situation as barrier to behaviours reducing stress and overweight. 3) Program activities related to reducing stress got more support from parents and professionals than activities related to reducing overweight.
Insight in the perspectives of disadvantaged parents and professionals resulted in a program plan supported by them, aiming to reduce stress and overweight. Most participating parents and professionals committed themselves to invest time in program activities execution.
Disadvantaged parents perceived reducing stress related to finances as top priority to improve family health. They perceived family finances as barrier to behaviours reducing stress and overweight.
Community-based participatory action research with disadvantaged parents and professionals can result in an integrated family health program plan with stakeholder support.
Biochar as a carrier : Trichoderma harzianum on Biochar to promote disease suppression in strawberry
Blok, Chris ; Diaz, Andrea ; Oud, Nina ; Streminska, Marta ; Huisman, Ming ; Khanh, Pham ; Fryda, Lydia ; Visser, Rianne - \ 2019
Bleiswijk : Wageningen University & Research, BU Greenhouse Horticulture (Report / Wageningen University & Research, BU Greenhouse Horticulture WPR-893) - 44
For the ministry of economic affairs, ECN (Energy Centre Netherlands, part of TNO) develops energy production from renewable organic sources. Pyrolysis and gasification are technologies by which green bio gas and platform chemicals can be produced. Another option is to co-produce bio-energy and biochar. Biochar is the high-carbon low-solid product of the process. The economic feasibility of the latter processes dependents on the valorisation of biochar. A promising application is as (partial) peat replacement option in potting soil mixtures for greenhouse horticultural production. Wageningen University & Research Greenhouse Horticulture used biochar in dedicated research to accomplish two distinct goals. The first goal was to use biochar as an environmentally more friendly peat alternative in potting soil mixes for the production of strawberries. The second goal was to use biochar as carrier for beneficial micro–organisms for the production of strawberries. In a cultivation experiment the growth effects in a range of biochar–peat mixtures was studied. Trichoderma was added to protect the plant against a wilful addition of the disease Phytophthora. The results show 10, 20 and 30% v/v of biochar in a peat soil does not affect fresh or dry weight production of leaf and stem mass. The biochar addition does increase the fruit fresh weight production with about 5-10%. The addition of Trichoderma with biochar did not lead to an improved survival of the Trichoderma in the potting soil mixes. The added Phytophthora did not lead to a higher disease incidence, but the Phytophthora presence is lower in treatments with a higher dose of biochar.
Erosion of archaeological sites: Quantifying the threat using optically stimulated luminescence and fallout isotopes
Huisman, H. ; Kort, J.W. de; Ketterer, M.E. ; Reimann, T. ; Schoorl, J.M. ; Heiden, M. van der; Soest, Maud van; Egmond, Fenny van - \ 2019
Geoarchaeology: an international journal 34 (2019)4. - ISSN 0883-6353 - p. 478 - 494.
Although visible evidence shows that erosion has damaged many archaeological sites, especially when tilled, there has hitherto been scant attention to its quantitative assessment. Accordingly, the archaeology communities lack insight into whether long‐term threats to the stability and integrity of soils at these sites allow these cultural repositories to be preserved for future human generations. Of the techniques that are available to measure erosion rates, few have been tested on the timescales needed. We selected three archaeological sites with high expected erosion rates. We combined optically stimulated luminescence (OSL) dating with analyses of radioactive fallout isotope distributions to assess erosion patterns and rates. An age–depth representation of OSL single‐aliquot results was developed to determine past erosion, and to identify stable land surfaces on centennial to millennia timescales. Fall‐out isotopes of cesium (Cs) and plutonium (Pu) were suitable for shorter timescales: The 240Pu/239Pu ratios and a correlation between activities of 239+240Pu and 137Cs demonstrated the weapons testing fallout origin of these isotopes in the ~1952–1966 timeframe. Erosion rates in recent decades ranged from 2 to 6 mm/year on the studied sites. Our results indicate that erosion is not only tied to the past, but keeps on threatening archaeological sites.
Fraud vulnerability in the Dutch milk supply chain : Assessments of farmers, processors and retailers
Yang, Y. ; Huisman, W. ; Hettinga, K.A. ; Liu, N. ; Heck, J. ; Schrijver, G.H. ; Gaiardoni, L. ; Ruth, S.M. van - \ 2019
Food Control 95 (2019). - ISSN 0956-7135 - p. 308 - 317.
Dairy supply chain - Fraud factor - Fraud mitigation - Milk adulteration - Organic farm - Vulnerability assessment
Food fraud surfaces regularly, anywhere in the world. Not only the companies involved in food fraud suffer from losses when food fraud occurs, other actors in the supply chain and branch of industry are often painted with the same brush. Milk has been a common fraud target in the past and, therefore, fraud is a concern for companies involved in milk production. In order to manage and prevent fraud in the milk supply chain, a good insight into the vulnerabilities of companies and their supply chain networks is pivotal. The aim of the current study is to understand (a) the fraud vulnerability of the general milk supply chain in the Netherlands and its tiers (farmers, processors, retailers) and (b) the differences in fraud vulnerability of farmers producing organic milk, green intermediate ‘pasture milk’ and conventional milk. The SSAFE food fraud assessment tool was slightly adapted to the milk supply chain and used to examine the fraud vulnerability of the 38 businesses of the three tiers in the study: 30 farmers, 4 milk processors and 4 retailers. Forty-eight fraud factors related to opportunities, motivations and control measures were examined. Subsequently, key fraud factors were identified. The three tier groups showed major similarities in motivation related fraud factors, and large differences in fraud opportunities and controls. There were also differences observed between the organic and non-organic farmers, with organic farmers being slightly more vulnerable than their non-organic counterparts. From this study it appears that the milk supply chain in the Netherlands is low to medium vulnerable to fraud but the key factors contributing to the vulnerability differ between the tiers (farmers, processors, retailers). Management of the fraud risks requires consideration of these differences.
Estuarine fish passes in the northern Netherlands provide contrasting windows of opportunity for migrating fish species (#188)
Huisman, Jeroen - \ 2018
Evergreen – bollen Plantengroei bevorderende rhizobacteriën
Dam, M.F.N. van; Breeuwsma, S.J. ; Huisman, Huei Ming ; Greve, Gerdit ; Wal, A. van der - \ 2018
- 1 p.
Archeologisch onderzoek in de omgeving van het prehistorische vuursteenmijnveld te Rijckholt - St.Geertruid : De resultaten van 2011, 2012 en 2013
Brinkkemper, O. ; Bruinink, A.C. ; Deeben, J. ; Guralnik, B. ; Hoebe, P. ; Huisman, H. ; Kort, J.W. de; Laarman, F. ; Meirvenne, M. van; Orbons, J. ; Os, B. van; Parys, V. van; Schreurs, J. ; Theunissen, L. ; Verhegge, J. ; Versendaal, Alice ; Wallinga, J. - \ 2018
Amersfoort : Rijksdienst voor het Cultureel Erfgoed - ISBN 9789057993022 - 371 p.
Formation of a symbiotic host-microbe interface: the role of SNARE-mediated regulation of exocytosis
Huisman, Rik - \ 2018
Wageningen University. Promotor(en): A.H.J. Bisseling, co-promotor(en): E.H.M. Limpens. - Wageningen : Wageningen University - ISBN 9789463323178 - 158
At the heart of endosymbiosis microbes are hosted inside living cells in specialized membrane compartments that from a host-microbe interface, where nutrients and signal are efficiently exchanged. Such symbiotic interfaces include arbuscules produced by arbuscular mycorrhiza (AM) and organelle-like symbiosomes formed during the rhizobium-legume symbiosis. Also during pathogenic interactions, microbes such as biotrophic fungi and oomycetes are hosted in specialized membrane compartments called haustoria. The formation of such new membrane compartments requires a major reorganization of the host endomembrane system, with a special role for the targeting of secretory/exocytotic vesicles and their cargo to the newly forming interfaces. In this thesis, I studied how exocytotic membrane traffic is regulated to facilitate the formation and maintenance of a host-microbe interface. Therefore, I especially focussed on the role of SNARE (Soluble NSF Attachment Protein Receptor) proteins, as key components of the exocytotic machinery, in symbiotic interface formation.
In Chapter 1, I introduce the different symbioses in which host-microbe interfaces are formed, and the role of the host-microbe interface in these symbioses. Further, I introduce the evolutionary relationship between the different symbioses: AM symbiosis is the most ancient endosymbiosis in plants, which provided the blueprint for different symbioses that evolved later; other symbiotic microbes including rhizobia co-opted the signalling program and adaptations to membrane trafficking required for arbuscule formation, to be hosted inside cells. Finally, I will introduce the symbiosis dedicated SNAREs as key regulators of exocytosis to form a host-microbe interface.
In Chapter 2, we tested the long-standing hypothesis that pathogens make use of the AM symbiotic program to allow the formation of haustoria. To test this, we set up a pathosystem using the biotrophic oomycete Phytophthora palmivora that is able to form haustoria in Medicago truncatula root cells. Using M. truncatula mutants impaired in AM and rhizobium symbioses, we demonstrated that neither the common symbiotic signalling genes, nor symbiosis dedicated regulators of vesicle trafficking are required for haustorium formation. This showed that biotrophic pathogens like P. palmivora, do not hijack the symbiotic program to be accommodated inside plant cells.
In Chapter 3, we identified the t-SNARE SYP132α as a key regulator of both arbuscule and symbiosome formation. During vesicle fusion, a vesicle SNARE (v-SNARE) on the vesicle forms a complex with a target membrane SNAREs (t-SNAREs) on the target membrane. Previous work in our lab identified specific exocytotic v-SNAREs required for arbuscule and symbiosome formation. We identified the t-SNARE counterpart SYP132, and demonstrated that in most dicot plants SYP132 is spliced into two spliceforms; SYP132α and SYP132β. Interestingly, alternative splicing of SYP132 leading to the dominant use of a SYP132α-specific last exon coincides with the accommodation of AM fungi in arbuscule forming root cortex cells and rhizobium bacteria in nodule cells. Using a spliceform-specific RNAi construct, we showed that SYP132α is specifically required for the formation of a stable host-microbe interface in both AM symbiosis and rhizobium symbiosis. Furthermore, we showed that during arbuscular collapse, the two spliceforms localize differently to healthy and degrading arbuscule branches. These results indicated that alternative splicing of SYP132 allows plants to replace a t-SNARE involved in traffic to the plasma membrane with a t-SNARE that is more stringent in its localization to functional arbuscules.
The evolutionary expansion of SNAREs in plants has been hypothesized to have allowed the adaptation of exocytosis to different biological processes. In Chapter 4, we studied what makes the symbiotic SNAREs so special in comparison to their non-symbiotic family members, of which many are also expressed in arbuscule cells. We hypothesized that symbiotic SNAREs define a distinct secretory pathway, that ensures specificity of protein delivery to the host-microbe interface. We show that all tested SYP1 family proteins, and most of the non-symbiotic VAMP72 members, were able to complement the defect in arbuscule formation upon knock-down of their symbiotic counterparts when expressed at sufficient levels. This functional redundancy is in line with the ability of all tested v- and t-SNARE combinations to form SNARE complexes at the peri-arbuscular membrane. This showed that the symbiotic SNAREs do not selectively interact to define a distinct vesicle trafficking pathway, but that their essential role in arbuscule formation can be largely explained by their dominant expression level. Interestingly, the symbiotic t-SNARE SYP132α appeared to occur less in SNARE complexes with v-SNAREs compared to the non-symbiotic syntaxins in the arbuscule cells, suggesting a more strict regulation of symbiotic SNARE complexes at the interface.
Since the alternative splicing of SYP132 does not affect the total transcript levels, we hypothesized that there must be a functional difference between SYP132α and –β, potentially leading to subtle phenotypes that may have gone undetected in the Agrobacterium rhizogenes mediated complementation approach applied in Chapter 4. In Chapter 5, we therefore generated and characterized a stable mutant line in which all SYP132 transcripts are constitutively spliced into the non-symbiotic SYP132β form. Although this mutant is normally colonized by AM fungi, with no effects on arbuscule morphology, it has a severely reduced biomass after mycorrhization. This hints to a yet unknown role for SYP132α to control arbuscule functionality, and offers an explanation for the evolutionary conservation of the SYP132 alternative splicing in dicot plants. Finally, using fluorescent timer fusions to both SYP132 isoforms, we showed that the difference in localization of the two proteins during arbuscular collapse is the result of a different (endocytic) turnover of the two spliceforms at the healthy/functional arbuscule branches, possibly due to a difference in interactions with VAMPs. Together, our data show that, although both SYP132 isoforms can mediate arbuscule formation, SYP132α is functionally different from SYP132β, which may reveal new aspects of the control of nutrient exchange.
In Chapter 6, I discuss the data generated during my thesis research in relation to additional symbiosis dedicated regulators of exocytosis, as well as in relation to other biological processes that depend on specific secretory SNAREs. Following our conclusion that the symbiotic SNAREs do not mark a separate exocytosis pathway, but are functionally different from non-symbiotic SNAREs, I will speculate on the possible scenarios in which symbiosis dedicated SNAREs are specialized for host-microbe interface functionality.
Does a high sugar high fat dietary pattern explain the unequal burden in prevalence of type 2 diabetes in a multi-ethnic population in the Netherlands? The HELIUS study
Huisman, Merel J. ; Soedamah-Muthu, Sabita S. ; Vermeulen, Esther ; Muilwijk, Mirthe ; Snijder, Marieke B. ; Nicolaou, Mary N. ; Valkengoed, Irene G.M. Van - \ 2018
Nutrients 10 (2018)1. - ISSN 2072-6643
HELIUS study - HSHF - Multi-ethnic - T2D - Western dietary pattern
The risk for type 2 diabetes (T2D) in ethnic minorities in Europe is higher in comparison with their European host populations. The western dietary pattern, characterized by high amounts of sugar and saturated fat (HSHF dietary pattern), has been associated with a higher risk for T2D. Information on this association in minority populations is scarce. Therefore, we aimed to investigate the HSHF dietary pattern and its role in the unequal burden of T2D prevalence in a multi-ethnic population in The Netherlands. We included 4694 participants aged 18-70 years of Dutch, South-Asian Surinamese, African Surinamese, Turkish, and Moroccan origin from the HELIUS study. Dutch participants scored the highest on the HSHF dietary pattern, followed by the Turkish, Moroccan, African Surinamese, and South-Asian Surinamese participants. Prevalence ratios (PR) for T2D were then calculated using multivariate cox regression analyses, adjusted for sociodemographic, anthropometric, and lifestyle factors. Higher adherence to an HSHF diet was not significantly related to T2D prevalence in the total study sample (PR 1.04 high versus low adherence, 95% CI: 0.80-1.35). In line, adjustment for HSHF diet score did not explain the ethnic differences in T2D. For instance, the PR of the South-Asian Surinamese vs. Dutch changed from 2.76 (95% CI: 2.05-3.72) to 2.90 (95% CI: 2.11-3.98) after adjustment for HSHF. To conclude, a western dietary pattern high in sugar and saturated fat was not associated with T2D, and did not explain the unequal burden in prevalence of T2D across the ethnic groups.