Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    Genetic variation in Sorghum bicolor strigolactones and their role in resistance against Striga hermonthica
    Mohemed, Nasreldin ; Charnikhova, Tatsiana ; Fradin, Emilie F. ; Rienstra, Juriaan ; Babiker, Abdelgabar G.T. ; Bouwmeester, Harro J. - \ 2018
    Journal of Experimental Botany 69 (2018)9. - ISSN 0022-0957 - p. 2415 - 2430.
    Germination stimulant - Parasitic weed - Resistance - Sorghum - Striga - Strigolactones

    Sorghum is an important food, feed, and industrial crop worldwide. Parasitic weeds of the genus Striga constitute a major constraint to sorghum production, particularly in the drier parts of the world. In this study we analysed the Striga germination stimulants, strigolactones, in the root exudates of 36 sorghum genotypes and assessed Striga germination and infection. Low germination-stimulating activity and low Striga infection correlated with the exudation of low amounts of 5-deoxystrigol and high amounts of orobanchol, whereas susceptibility to Striga and high germination- stimulating activity correlated with high concentrations of 5-deoxystrigol and low concentrations of orobanchol. Marker analysis suggested that similar genetics to those previously described for the resistant sorghum variety SRN39 and the susceptible variety Shanqui Red underlie these differences. This study shows that the strigolactone profile in the root exudate of sorghum has a large impact on the level of Striga infection. High concentrations of 5-deoxystrigol result in high infection, while high concentrations of orobanchol result in low infection. This knowledge should help to optimize the use of low germination stimulant-based resistance to Striga by the selection of sorghum genotypes with strigolactone profiles that favour normal growth and development, but reduce the risk of Striga infection.

    Corrigendum to: Abscisic acid influences tillering by modulation of strigolactones in barley
    Wang, Hongwen ; Chen, Wanxin ; Eggert, Kai ; Charnikhova, Tatsiana ; Bouwmeester, Harro ; Schweizer, Patrick ; Hajirezaei, Mohammad R. ; Seiler, Christiane ; Sreenivasulu, Nese ; Wirén, Nicolaus von; Kuhlmann, Markus - \ 2018
    Journal of Experimental Botany 69 (2018)21. - ISSN 0022-0957 - p. 5307 - 5307.
    Abscisic acid influences tillering by modulation of strigolactones in barley
    Wang, Hongwen ; Chen, Wanxin ; Eggert, Kai ; Charnikhova, Tatsiana ; Bouwmeester, Harro ; Schweizer, Patrick ; Hajirezaei, Mohammad R. ; Seiler, Christiane ; Sreenivasulu, Nese ; Wirén, Nicolaus von; Kuhlmann, Markus - \ 2018
    Journal of Experimental Botany 69 (2018)16. - ISSN 0022-0957 - p. 3883 - 3898.
    Abscisic acid - barley - cereals - hormone regulation - phytohormone cross-talk - shoot branching - strigolactone biosynthesis - tillering

    Strigolactones (SLs) represent a class of plant hormones that are involved in inhibiting shoot branching and in promoting abiotic stress responses. There is evidence that the biosynthetic pathways of SLs and abscisic acid (ABA) are functionally connected. However, little is known about the mechanisms underlying the interaction of SLs and ABA, and the relevance of this interaction for shoot architecture. Based on sequence homology, four genes (HvD27, HvMAX1, HvCCD7, and HvCCD8) involved in SL biosynthesis were identified in barley and functionally verified by complementation of Arabidopsis mutants or by virus-induced gene silencing. To investigate the influence of ABA on SLs, two transgenic lines accumulating ABA as a result of RNAi-mediated down-regulation of HvABA 8'-hydroxylase 1 and 3 were employed. LC-MS/MS analysis confirmed higher ABA levels in root and stem base tissues in these transgenic lines. Both lines showed enhanced tiller formation and lower concentrations of 5-deoxystrigol in root exudates, which was detected for the first time as a naturally occurring SL in barley. Lower expression levels of HvD27, HvMAX1, HvCCD7, and HvCCD8 indicated that ABA suppresses SL biosynthesis, leading to enhanced tiller formation in barley.

    Zeapyranolactone − A novel strigolactone from maize
    Charnikhova, Tatsiana V. ; Gaus, Katharina ; Lumbroso, Alexandre ; Sanders, Mark ; Vincken, Jean Paul ; Mesmaeker, Alain De; Ruyter-Spira, Carolien P. ; Screpanti, Claudio ; Bouwmeester, Harro J. - \ 2018
    Phytochemistry Letters 24 (2018). - ISSN 1874-3900 - p. 172 - 178.
    Maize (Zea mays) - NMR - Prep-HPLC–MS - Strigolactones - Zeapyranolactone
    The structure of a new strigolactone present in the root exudate and root extract of maize hybrid cv NK Falkone plants was elucidated and characterized as zeapyranolactone: Methyl.(E)-3-((4-methyl-5-oxo-2,5-dihydrofuran-2-yl)oxy)-2-(4,4,5-trimethyl-2-oxo-2,3,4,6,7,7a-hexahydrocyclopenta[b]pyran-7-yl)acrylate. Unlike any other strigolactone published so far, it contains a 4,4-dimethyltetrahydropyran-2-one as A ring. The impact of the elucidation of this structure on the earlier postulated biosynthetic pathway of another maize strigolactone, zealactone, is discussed.
    Zealactones. Novel natural strigolactones from maize
    Charnikhova, Tatsiana V. ; Gaus, Katharina ; Lumbroso, Alexandre ; Sanders, Mark ; Vincken, Jean Paul ; Mesmaeker, Alain de; Ruyter-Spira, Carolien P. ; Screpanti, Claudio ; Bouwmeester, Harro J. - \ 2017
    Phytochemistry 137 (2017). - ISSN 0031-9422 - p. 123 - 131.
    Maize (Zea mays) - NMR - Prep-HPLC-MS - Seed germination - Striga hermonthica (Orobanchaceae) - Strigolactones - UHPLC-MS-MS - Zealactone

    In the root exudate and root extracts of maize hybrid cv NK Falkone seven putative strigolactones were detected using UPLC-TQ-MS-MS. All seven compounds displayed MS-MS-fragmentation common for strigolactones and particularly the presence of a fragment of m/z 97 Da, which may indicate the presence of the so-called D-ring, suggests they are strigolactones. The levels of all these putative strigolactones increased upon phosphate starvation and decreased upon fluridone (carotenoid biosynthesis inhibitor) treatment, both of which are a common response for strigolactones. All seven compounds were subsequently isolated with prep-HPLC-MS. They all exhibited Striga hermonthica seed germination inducing activity just as the synthetic strigolactone analog GR24. The structure of two of the seven compounds was elucidated by NMR spectroscopy as: methyl (2E,. 3E)-4-(3,. 3-dimethyl-5-oxo-2-(prop-1-en-2-yl)tetrahydrofuran-2-yl)-2-(((4-methyl-5-oxo-2,. 5-dihydrofuran-2-yl)oxy)methylene)but-3-enoate (two diastereomers 1a and 1b). Strigolactones (1a/b) are closely related to the methyl ester of carlactonoic acid (MeCLA) and heliolactone. However, they contain a unique 4,4-dimethyltetrahydrofuran-2-one motif as the "A-ring" instead of the classical (di)methylcyclohexene. Because these compounds were isolated from maize (Zea mays) we called them "zealactone 1a and 1b". The implications of this discovery for our view on strigolactones and their biosynthesis are discussed.

    Characterization of low-strigolactone germplasm in pea (Pisum sativum L.) resistant to crenate broomrape (Orobanche crenata Forsk.)
    Pavan, Stefano ; Schiavulli, Adalgisa ; Marcotrigiano, Angelo Raffaele ; Bardaro, Nicoletta ; Bracuto, Valentina ; Ricciardi, Francesca ; Charnikhova, Tatsiana ; Lotti, Concetta ; Bouwmeester, Harro ; Ricciardi, Luigi - \ 2016
    Molecular Plant-Microbe Interactions 29 (2016)10. - ISSN 0894-0282 - p. 743 - 749.

    Crenate broomrape (Orobanche crenata Forsk.) is a devastating parasitic weed threatening the cultivation of legumes around the Mediterranean and in theMiddle East. So far, only moderate levels of resistance were reported to occur in pea (Pisum sativum L.) natural germplasm, and most commercial cultivars are prone to severe infestation. Here, we describe the selection of a pea line highly resistant to O. crenata, following the screening of local genetic resources. Time series observations show that delayed emergence of the parasite is an important parameter associated with broomrape resistance. High performance liquid chromatography connected to tandem mass spectrometry analysis and in vitro broomrape germination bioassays suggest that the resistance mechanism might involve the reduced secretion of strigolactones, plant hormones exuded by roots and acting as signaling molecules for the germination of parasitic weeds. Two years of replicated trials in noninfested fields indicate that the resistance is devoid of pleiotropic effects on yield, in contrast to pea experimental mutants impaired in strigolactone biosynthesis and, thus, is suitable for use in breeding programs.

    Evaluation of field resistance to Striga hermonthica (Del.) Benth. in Sorghum bicolor (L.) Moench. The relationship with strigolactones
    Mohemed Ahmed Mohamed, Nasr Eldin ; Charnikhova, Tatsiana ; Bakker, Evert J. ; Ast, Aad van; Babiker, Abdelgabar Gt ; Bouwmeester, Harro J. - \ 2016
    Pest Management Science 72 (2016)11. - ISSN 1526-498X - p. 2082 - 2090.
    Resistance - Sorghum - Striga - Strigolactones

    BACKGROUND: Significant losses in sorghum biomass and grain yield occur in sub-Saharan Africa owing to infection by the root-parasitic weed Striga hermonthica (Del.) Benth. One strategy to avoid these losses is to adopt resistant crop varieties. For further delineation of the role of germination stimulants in resistance, we conducted a field experiment employing six sorghum genotypes, in eastern Sudan, and in parallel analysed the strigolactone levels in the root exudates of these genotypes under controlled conditions in Wageningen. RESULTS: The root exudates of these genotypes displayed large differences in strigolactone composition and Striga-germination-inducing activity. Korokollow, Fakimustahi and Wadfahel exuded the highest amounts of 5-deoxystrigol. Fakimustahi was by far the highest sorgomol producer, and Wadbaco and SRN39 produced the highest amount of orobanchol. The concentration of 5-deoxystrigol in the root exudate showed a significant positive correlation with in vitro Striga germination and was positively associated with Striga infection in the field experiments, whereas orobanchol was negatively associated with Striga infection in the field experiments. CONCLUSION: For the first time a close association is reported between strigolactone levels analysed under laboratory conditions and Striga infection in the field in sorghum genotypes. These genotypes may be used for further study of this resistance mechanism and for the introgression of the low germination trait in other sorghum varieties to breed for a strigolactone composition with low stimulant activity. The use of such improved varieties in combination with other Striga management tools could possibly alleviate the current Striga problem on the African continent.

    Osmotic stress represses strigolactone biosynthesis in Lotus japonicus roots: exploring the interaction between strigolactones and ABA under abiotic stress
    Liu, J. ; He, H. ; Vitali, M. ; Visentin, I. ; Charnikhova, T. ; Haider, I. ; Schubert, A. ; Ruyter-Spira, C.P. - \ 2015
    Planta 241 (2015)6. - ISSN 0032-0935 - p. 1435 - 1451.
    Main conclusion Strigolactone changes and cross talk with ABA unveil a picture of root-specific hormonal dynamics under stress. Abstract Strigolactones (SLs) are carotenoid-derived hormones influencing diverse aspects of development and communication with (micro)organisms, and proposed as mediators of environmental stimuli in resource allocation processes; to contribute to adaptive adjustments, therefore, their pathway must be responsive to environmental cues. To investigate the relationship between SLs and abiotic stress in Lotus japonicus, we compared wild-type and SLdepleted plants, and studied SL metabolism in roots stressed osmotically and/or phosphate starved. SL-depleted plants showed increased stomatal conductance, both under normal and stress conditions, and impaired resistance to drought associated with slower stomatal closure in response to abscisic acid (ABA). This confirms that SLs contribute to drought resistance in species other than Arabidopsis. However, we also observed that osmotic stress rapidly and strongly decreased SL concentration in tissues and exudates of wild-type Lotus roots, by acting on the transcription of biosynthetic and transporter-encoding genes and independently of phosphate abundance. Pretreatment with exogenous SLs inhibited the osmotic stressinduced ABA increase in wild-type roots and downregulated the transcription of the ABA biosynthetic gene
    Rhizobium lipo-chitooligosaccharide signaling triggers accumulation of cytokinins in Medicago truncatula roots
    Zeijl, A.L. van; Camp, R.H.M. Op den; Deinum, E.E. ; Charnikhova, T. ; Franssen, H. ; Camp, H.J.M. op den; Bouwmeester, H.J. ; Kohlen, W. ; Bisseling, T. ; Geurts, R. - \ 2015
    Molecular Plant 8 (2015)8. - ISSN 1674-2052 - p. 1213 - 1226.
    Legume rhizobium symbiosis is initiated upon perception of bacterial secreted lipo-chitooligosaccharides (LCOs). Perception of these signals by the plant initiates a signaling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accumulation and subsequent signaling are an integral part of rhizobium LCO signaling remains elusive. Here, we show that cytokinin signaling is required for the majority of transcriptional changes induced by rhizobium LCOs. In addition, we demonstrate that several cytokinins accumulate in the root susceptible zone 3 h after rhizobium LCO application, including the biologically most active cytokinins, trans-zeatin and isopentenyl adenine. These responses are dependent on calcium- and calmodulin-dependent protein kinase (CCaMK), a key protein in rhizobial LCO-induced signaling. Analysis of the ethylene-insensitive Mtein2/Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signaling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.
    Rice cytochrome P450 MAX1 homologs catalyze distinct steps in strigolactone biosynthesis
    Zhang, Y. ; Dijk, A.D.J. van; Scaffidi, A. ; Flematti, G.R. ; Hofmann, M. ; Charnikhova, T. ; Verstappen, F.W.A. ; Hepworth, J. ; Krol, A.R. van der; Leyser, O. - \ 2014
    Nature Chemical Biology 10 (2014). - ISSN 1552-4450 - p. 1028 - 1033.
    arbuscular mycorrhizal fungi - structural requirements - germination stimulants - biological-activities - arabidopsis-thaliana - crystal-structures - plant hormones - protein - inhibition - expression
    Strigolactones (SLs) are a class of phytohormones and rhizosphere signaling compounds with high structural diversity. Three enzymes, carotenoid isomerase DWARF27 and carotenoid cleavage dioxygenases CCD7 and CCD8, were previously shown to convert all-trans-¿-carotene to carlactone (CL), the SL precursor. However, how CL is metabolized to SLs has remained elusive. Here, by reconstituting the SL biosynthetic pathway in Nicotiana benthamiana, we show that a rice homolog of Arabidopsis MORE AXILLARY GROWTH 1 (MAX1), encodes a cytochrome P450 CYP711 subfamily member that acts as a CL oxidase to stereoselectively convert CL into ent-2'-epi-5-deoxystrigol (B-C lactone ring formation), the presumed precursor of rice SLs. A protein encoded by a second rice MAX1 homolog then catalyzes the conversion of ent-2'-epi-5-deoxystrigol to orobanchol. We therefore report that two members of CYP711 enzymes can catalyze two distinct steps in SL biosynthesis, identifying the first enzymes involved in B-C ring closure and a subsequent structural diversification step of SLs.
    Differential Activity of Striga hermonthica Seed Germination Stimulants and Gigaspora rosea Hyphal Branching Factors in Rice and Their Contribution to Underground Communication
    Cardoso, C. ; Charnikhova, T. ; Jamil, M. ; Delaux, P.M. ; Verstappen, F.W.A. ; Amini, M. ; Lauressergues, D. ; Ruyter-Spira, C.P. ; Bouwmeester, H.J. - \ 2014
    PLoS ONE 9 (2014)8. - ISSN 1932-6203
    arbuscular mycorrhizal fungi - strigolactone production - structural requirements - phosphorus deficiency - phosphate deficiency - gesnerioides seeds - plant hormones - root parasites - red-clover - inhibition
    Strigolactones (SLs) trigger germination of parasitic plant seeds and hyphal branching of symbiotic arbuscular mycorrhizal (AM) fungi. There is extensive structural variation in SLs and plants usually produce blends of different SLs. The structural variation among natural SLs has been shown to impact their biological activity as hyphal branching and parasitic plant seed germination stimulants. In this study, rice root exudates were fractioned by HPLC. The resulting fractions were analyzed by MRM-LC-MS to investigate the presence of SLs and tested using bioassays to assess their Striga hermonthica seed germination and Gigaspora rosea hyphal branching stimulatory activities. A substantial number of active fractions were revealed often with very different effect on seed germination and hyphal branching. Fractions containing (-)-orobanchol and ent-2'-epi-5-deoxystrigol contributed little to the induction of S. hermonthica seed germination but strongly stimulated AM fungal hyphal branching. Three SLs in one fraction, putative methoxy-5-deoxystrigol isomers, had moderate seed germination and hyphal branching inducing activity. Two fractions contained strong germination stimulants but displayed only modest hyphal branching activity. We provide evidence that these stimulants are likely SLs although no SL-representative masses could be detected using MRM-LC-MS. Our results show that seed germination and hyphal branching are induced to very different extents by the various SLs (or other stimulants) present in rice root exudates. We propose that the development of rice varieties with different SL composition is a promising strategy to reduce parasitic plant infestation while maintaining symbiosis with AM fungi.
    OsJAR1 is required for JA-regulated floret opening and anther dehiscence in rice
    Xiao, Y. ; Charnikhova, T. ; Mulder, P.P.J. ; Heijmans, J. ; Hoogenboom, A. ; Agalou, A. ; Michel, C. ; Morel, J.B. ; Dreni, L. ; Kater, M.M. ; Bouwmeester, H.J. ; Wang, B. ; Zhu, Z. ; Ouwerkerk, P.B.F. - \ 2014
    Plant Molecular Biology 86 (2014)1-2. - ISSN 0167-4412 - p. 19 - 33.
    jasmonic acid biosynthesis - male-sterile mutant - l-isoleucine - methyl jasmonate - gene encodes - arabidopsis - enzyme - proteins - tomato - (+)-7-iso-jasmonoyl-l-isoleucine
    Jasmonates are important phytohormones regulating reproductive development. We used two recessive rice Tos17 alleles of OsJAR1, osjar1-2 and osjar1-3, to study the biological function of jasmonates in rice anthesis. The florets of both osjar1 alleles stayed open during anthesis because the lodicules, which control flower opening in rice, were not withering on time. Furthermore, dehiscence of the anthers filled with viable pollen, was impaired, resulting in lower fertility. In situ hybridization and promoter GUS transgenic analysis confirmed OsJAR1 expression in these floral tissues. Flower opening induced by exogenous applied methyl jasmonate was impaired in osjar1 plants and was restored in a complementation experiment with transgenics expressing a wild type copy of OsJAR1 controlled by a rice actin promoter. Biochemical analysis showed that OsJAR1 encoded an enzyme conjugating jasmonic acid (JA) to at least Ile, Leu, Met, Phe, Trp and Val and both osjar1 alleles had substantial reduction in content of JA-Ile, JA-Leu and JA-Val in florets. We conclude that OsJAR1 is a JA-amino acid synthetase that is required for optimal flower opening and closing and anther dehiscence in rice
    Influence of Fertilizer Microdosing on Strigolactone Production and Striga hermonthica Parasitism in Pearl Millet
    Jamil, M. ; Charnikhova, T. ; Jamil, T. ; Ali, Z. ; Mohemed Ahmed Mohamed, N.E. ; Mourik, T. van; Bouwmeester, H.J. - \ 2014
    International Journal of Agriculture & Biology 16 (2014). - ISSN 1560-8530 - p. 935 - 940.
    sorghum-bicolor - infestation - resistance - attachment - cultivars - africa
    Parasitism by the root-parasitic plant, Striga (Striga hermonthica L.), is a main threat to pearl millet production in sub-Saharan Africa and nutrient deficiency aggravates this problem, often leading to complete failure of pearl millet crops. Like many other species, pearl millet secretes germination stimulants (strigolactones) into the soil in response to mineral nutrient deficiency, which triggers Striga seed germination resulting in infection. A greenhouse experiment was conducted to evaluate the influence of different doses of di-ammonium phosphate (DAP) fertilizer on strigolactone production and Striga infection in three different African pearl millet cultivars (KBH, Sadore Local and Striga resistance). All the pearl millet genotypes produced varying amounts of different strigolactones like orobanchol, epi-orobanchol, orobanchyl acetate and 5-deoxystrigol, the level of which decreases with increasing doses of DAP. The control treatment (no DAP) showed maximum Striga germination, emergence and dry biomass production in all cultivars of pearl millet. Supply of DAP fertilizer up to 4 g per hill suppressed Striga germination by 69, 64 and 59%; emergence by 87, 85 and 95% and dry biomass by 91, 98 and 83% in cvs KBH, Sadore Local and Striga Resistance, respectively. The present findings reveal that DAP fertilizer minimizes strigolactones production and, as a result, reduces Striga infection in pearl millet. Low doses of DAP fertilizer is a promising strategy to lower the destructive effect of Striga on pearl millet. The use of small doses of DAP fertilizer combined with resistant crop cultivars, intercropping with legumes and hand pulling of Striga at flowering in an integrated Striga control strategy should be developed to help African farmers control this noxious weed.
    Striga hermonthica MAX2 restores branching but not the Very Low Fluence Response in the Arabidopsis thaliana max2 mutant
    Liu, Q. ; Zhang, Y. ; Matusovaa, R. ; Charnikhova, T. ; Amini, M. ; Jamil, M. ; Fernandez-Aparicio, M. ; Huang, K. ; Timko, M.P. ; Westwood, J.H. ; Ruyter-Spira, C.P. ; Krol, A.R. van der; Bouwmeester, H.J. - \ 2014
    New Phytologist 202 (2014)2. - ISSN 0028-646X - p. 531 - 541.
    arabidopsis seed-germination - box protein max2 - plant hormone - strigolactone - inhibition - photomorphogenesis - stimulants - karrikins - molecule - pathway
    Seed germination of Striga spp. (witchweeds), one of the world’s most destructive parasitic weeds, cannot be induced by light but is specifically induced by strigolactones. It is not known whether Striga uses the same components for strigolactone signaling as host plants, whether it has endogenous strigolactone biosynthesis and whether there is post-germination strigolactone signaling in Striga. Strigolactones could not be detected in in vitro grown Striga, while for host-grown Striga, the strigolactone profile is dominated by a subset of the strigolactones present in the host. Branching of in vitro grown Striga is affected by strigolactone biosynthesis inhibitors. ShMAX2, the Striga ortholog of Arabidopsis MORE AXILLARY BRANCHING 2 (AtMAX2) – which mediates strigolactone signaling – complements several of the Arabidopsis max2-1 phenotypes, including the root and shoot phenotype, the High Irradiance Response and the response to strigolactones. Seed germination of max2-1 complemented with ShMAX2 showed no complementation of the Very Low Fluence Response phenotype of max2-1. Results provide indirect evidence for ShMAX2 functions in Striga. A putative role of ShMAX2 in strigolactone-dependent seed germination of Striga is discussed.
    Effect of phosphate-based seed priming on strigolactone production and Striga hermonthica infection in cereals
    Jamil, M. ; Charnikhova, T. ; Verstappen, F.W.A. ; Ali, Z. ; Wainwright, H. ; Bouwmeester, H.J. - \ 2014
    Weed Research 54 (2014)3. - ISSN 0043-1737 - p. 307 - 313.
    arbuscular mycorrhizal fungi - phosphorus deficiency - root parasites - sorghum - plants - management - exudation - promotes - africa - growth
    Strigolactones, plant-secreted underground signalling molecules, play an important role in agricultural ecosystems, because they mediate the interaction of crops with symbiotic AM fungi and parasitic weeds like Striga hermonthica. Cereal host plants secret these signalling molecules particularly under nutrient-deficient conditions and especially when phosphate (P) is limiting. The objective of the present study was to see the potential of P seed priming for S. hermonthica management in cereals in relation to strigolactone production. It has been demonstrated that P fertiliser application down-regulates the production of these signalling molecules in the rhizosphere, which results in lower S. hermonthica infection of cereals. The laboratory study showed maximum production of strigolactones from dry and water-soaked seeds, while seed soaking in P solution reduced their production. Similarly, maximum S. hermonthica infection was observed under control treatments with dry sowing or water soaking, while P seed soaking decreased S. hermonthica germination, emergence and dry biomass in all cereal crops. Our study shows that P seed priming resulted in lower exudation of strigolactones, which induced less S. hermonthica seeds germination and hence may lead to lower S. hermonthica infection. P-based seed priming could prove to be an effective and affordable strategy to reduce S. hermonthica infection in cereals. Further research for practical field application is needed
    Natural variation of rice strigolactone biosynthesis is associated with the deletion of two MAX1 orthologs
    Cardoso, C. ; Zhang, Y. ; Jamil, M. ; Hepworth, J. ; Charnikhova, T. ; Dimkpa, S.O.N. ; Reiff, C. ; Wright, M.H. ; Liu, J. ; Meng, X. ; Bouwmeester, H.J. ; Ruyter-Spira, C.P. - \ 2014
    Proceedings of the National Academy of Sciences of the United States of America 111 (2014)6. - ISSN 0027-8424 - p. 2379 - 2384.
    arbuscular mycorrhizal fungi - quantitative trait loci - tiller bud outgrowth - striga-hermonthica - oryza-sativa - phosphate deficiency - root morphology - arabidopsis - architecture - inhibition
    Rice (Oryza sativa) cultivar Azucena—belonging to the Japonica subspecies—exudes high strigolactone (SL) levels and induces high germination of the root parasitic plant Striga hermonthica. Consistent with the fact that SLs also inhibit shoot branching, Azucena is a lowtillering variety. In contrast, Bala, an Indica cultivar, is a low-SL producer, stimulates less Striga germination, and is highly tillered. Using a Bala × Azucena F6 population, a major quantitative trait loci— qSLB1.1—for the exudation of SL, tillering, and induction of Striga germination was detected on chromosome 1. Sequence analysis of the corresponding locus revealed a rearrangement of a 51- to 59-kbp stretch between 28.9 and 29 Mbp in the Bala genome, resulting in the deletion of two cytochrome P450 genes—SLB1 and SLB2—with high homology to the Arabidopsis SL biosynthesis gene, MAX1. Both rice genes rescue the Arabidopsis max1-1 highly branched mutant phenotype and increase the production of the SL, ent-2'-epi-5-deoxystrigol, when overexpressed in Bala. Furthermore, analysis of this region in 367 cultivars of the publicly available Rice Diversity Panel population shows that the rearrangement at this locus is a recurrent natural trait associated with the Indica/Japonica divide in rice.
    CAROTENOID CLEAVAGE DIOXYGENASE 7 modulates plant growth, reproduction, senescence, and determinate nodulation in the model legume Lotus japonicas
    Liu, J. ; Novero, M. ; Charnikhova, T. ; Ferrandino, A. ; Schubert, A. ; Ruyter-Spira, C.P. ; Biofante, P. ; Lovisolo, C. ; Bouwmeester, H.J. - \ 2013
    Journal of Experimental Botany 64 (2013)7. - ISSN 0022-0957 - p. 1967 - 1981.
    strigolactone analog gr24 - f-box protein - leaf senescence - germination stimulants - seed-germination - parasitic plants - key component - am fungi - arabidopsis - rice
    Strigolactones (SLs) are newly identified hormones that regulate multiple aspects of plant development, infection by parasitic weeds, and mutualistic symbiosis in the roots. In this study, the role of SLs was studied for the first time in the model plant Lotus japonicus using transgenic lines silenced for CAROTENOID CLEAVAGE DIOXYGENASE 7 (LjCCD7), the orthologue of Arabidopsis More Axillary Growth 3. Transgenic LjCCD7-silenced plants displayed reduced height due to shorter internodes, and more branched shoots and roots than the controls, and an increase in total plant biomass, while their root:shoot ratio remained unchanged. Moreover, these lines had longer primary roots, delayed senescence, and reduced flower/pod numbers from the third round of flower and pod setting onwards. Only a mild reduction in determinate nodule numbers and hardly any impact on the colonization by arbuscular mycorrhizal fungi were observed. The results show that the impairment of CCD7 activity in L. japonicus leads to a phenotype linked to SL functions, but with specific features possibly due to the peculiar developmental pattern of this plant species. It is believed that the data also link determinate nodulation, plant reproduction, and senescence to CCD7 function for the first time.
    New strigolactone mimics: structure-activity relationship and mode of action as germinating stimulants for parasitic weeds.
    Zwanenburg, B. ; Nayak, S.K. ; Charnikhova, T. ; Bouwmeester, H.J. - \ 2013
    Bioorganic and Medicinal Chemistry Letters 23 (2013)18. - ISSN 0960-894X - p. 5182 - 5186.
    seed-germination - orobanche-minor - plant hormones - am fungi - striga-hermonthica - red-clover - analogs - inhibition - ring - phelipanche
    Strigolactones (SLs) are new plant hormones with varies important bio-functions. This Letter deals with germination of seeds of parasitic weeds. Natural SLs have a too complex structure for synthesis. Therefore, there is an active search for SL analogues and mimics with a simpler structure with retention of activity. SL analogues all contain the D-ring connected with an enone moiety through an enol ether unit. A new mechanism for the hydrolysis SL analogues involving bidentate bound water and an a,ß-hydrolase with a Ser-His-Asp catalytic triad has been proposed. Newly discovered SL mimics only have the D-ring with an appropriate leaving group at C-5. A mode of action for SL mimics was proposed for which now supporting evidence is provided. As predicted an extra methyl group at C-4 of the D-ring blocks the germination of seeds of parasitic weeds.
    ABA-deficiency results in reduced plant and fruit size in tomato
    Nitsch, L. ; Kohlen, W. ; Oplaat, C. ; Charnikhova, T. ; Cristescu, S. ; Michieli, P. ; Wolters-Arts, M. ; Bouwmeester, H.J. ; Mariani, C. ; Vriezen, W.H. ; Rieu, I. - \ 2012
    Journal of Plant Physiology 169 (2012)9. - ISSN 0176-1617 - p. 878 - 883.
    abscisic-acid biosynthesis - shoot growth - arabidopsis-thaliana - endogenous aba - ethylene - mutants - drought - stress - gene - expression
    Abscisic acid (ABA) deficient mutants, such as notabilis and flacca, have helped elucidating the role of ABA during plant development and stress responses in tomato (Solanum lycopersicum L.). However, these mutants have only moderately decreased ABA levels. Here we report on plant and fruit development in the more strongly ABA-deficient notabilis/flacca (not/flc) double mutant. We observed that plant growth, leaf-surface area, drought-induced wilting and ABA-related gene expression in the different genotypes were strongly correlated with the ABA levels and thus most strongly affected in the not/flc double mutants. These mutants also had reduced fruit size that was caused by an overall smaller cell size. Lower ABA levels in fruits did not correlate with changes in auxin levels, but were accompanied by higher ethylene evolution rates. This suggests that in a wild-type background ABA stimulates cell enlargement during tomato fruit growth via a negative effect on ethylene synthesis.
    The tomato CAROTENOID CLEAVAGE DIOXYGENASE8 (SlCCD8) regulates rhizosphere signaling, plant architecture and affects reproductive development through strigolactone biosynthesis
    Kohlen, W. ; Charnikhova, T. ; Lammers, M. ; Pollina, T. ; Toth, P. ; Haider, I. ; Pozo, M.J. ; Maagd, R.A. de; Ruyter-Spira, C.P. ; Bouwmeester, H.J. ; Lopez-Raez, J.A. - \ 2012
    New Phytologist 196 (2012)2. - ISSN 0028-646X - p. 535 - 547.
    arbuscular mycorrhizal fungi - tiller bud outgrowth - phosphate deficiency - parasitic plants - orobanche spp. - arabidopsis - gene - mutant - germination - rice
    •Strigolactones are plant hormones that regulate both above- and belowground plant architecture. Strigolactones were initially identified as rhizosphere signaling molecules. In the present work, the tomato (Solanum lycopersicum) CAROTENOID CLEAVAGE DIOXYGENASE 8 (SlCCD8) was cloned and its role in rhizosphere signaling and plant physiology assessed by generating knock-down lines. •Transgenic SlCCD8 plants were generated by RNAi-mediated silencing. Lines with different levels of strigolactone reduction – confirmed by UPLC-MS/MS – were selected and their phenotypes investigated. •Lines exhibiting reduced SlCCD8 levels displayed increased shoot branching, reduced plant height, increased number of nodes and excessive adventitious root development. In addition, these lines exhibited reproductive phenotypes such as smaller flowers, fruits, as well as fewer and smaller seeds per fruit. Furthermore, we show that strigolactone loading to the xylem sap is possibly restricted to orobanchol. •Infestation by Phelipanche ramosa was reduced by 90% in lines with a relatively mild reduction in strigolactone biosynthesis and secretion while arbuscular mycorrhizal symbiosis, apical dominance and fruit yield were only mildly affected. This demonstrates that reduction of strigolactone biosynthesis could be a suitable tool in parasitic weed management. Furthermore, our results suggest that strigolactones are involved in even more physiological processes than so far assumed.
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