Opening of Iris flowers is regulated by endogenous auxins
Doorn, W.G. van; Dole, I. ; Celikel, F.G. ; Harkema, H. - \ 2013
Journal of Plant Physiology 170 (2013)2. - ISSN 0176-1617 - p. 161 - 164.
ipomoea-nil convolvulaceae - ethylene - arabidopsis - corolla - growth - acid - gibberellin - elongation - roles
Flower opening in Iris (Iris x hollandica) requires elongation of the pedicel and ovary. This moves the floral bud upwards, thereby allowing the tepals to move laterally. Flower opening is requires with elongation of the pedicel and ovary. In cv. Blue Magic, we investigated the possible role of hormones other than ethylene in pedicel and ovary elongation and flower opening. Exogenous salicylic acid (SA) and the cytokinins benzyladenine (N6-benzyladenine, BA) and zeatin did not affect opening. Jasmonic acid (JA) and abscisic acid (ABA) were slightly inhibitory, but an inhibitor of ABA synthesis' (norflurazon) was without effect. Flower opening was promoted by gibberellic acid (GA(3)), but two inhibitors of gibberellin synthesis (4-hydroxy-5-isopropyl-2-methylphenyltrimethyl ammonium chloride-l-piperidine carboxylate, AMO-1618; ancymidol) did not change opening. The auxins indoleacetic acid (IAA) and naphthaleneacetic acid (NAA) strongly promoted elongation and opening. An inhibitor of auxin transport (2,3,5-triodobenzoic acid, TIBA) and an inhibitor of auxin effects [alpha-(p-chlorophenoxy)-isobutyric acid; PCIB] inhibited elongation and opening. The data suggest that endogenous auxins are among the regulators of the pedicel and ovary elongation and thus of flower opening in Iris. (C) 2012 Elsevier GmbH. All rights reserved.
ABA Inhibits Embryo Cell Expansion and Early Cell Division Events During Coffee (Coffea arabica 'Rubi') Seed Germination
Silva, E.A.A. da; Toorop, P.E. ; Lammeren, A.A.M. van; Hilhorst, H.W.M. - \ 2008
Annals of Botany 102 (2008)3. - ISSN 0305-7364 - p. 425 - 433.
abscisic-acid - tomato seeds - endosperm development - arabidopsis-thaliana - replication - gibberellin - cytoskeleton - deficient - dormancy
Background and Aims: Coffee seed germination represents an interplay between the embryo and the surrounding endosperm. A sequence of events in both parts of the seed determines whether germination will be successful or not. Following previous studies, the aim here was to further characterize the morphology of endosperm degradation and embryo growth with respect to morphology and cell cycle, and the influence of abscisic acid on these processes. Methods: Growth of cells in a fixed region of the axis was quantified from light micrographs. Cell cycle events were measured by flow cytometry and by immunocytochemistry, using antibodies against ß-tubulin. Aspects of the endosperm were visualized by light and scanning electron microscopy. Key Results: The embryonic axis cells grew initially by isodiametric expansion. This event coincided with reorientation and increase in abundance of microtubules and with accumulation of ß-tubulin. Radicle protrusion was characterized by a shift from isodiametric expansion to elongation of radicle cells and further accumulation of ß-tubulin. Early cell division events started prior to radicle protrusion. Abscisic acid decreased the abundance of microtubules and inhibited the growth of the embryo cells, the reorganization of the microtubules, DNA replication in the embryonic axis, the formation of a protuberance and the completion of germination. The endosperm cap cells had smaller and thinner cell walls than the rest of the endosperm. Cells in the endosperm cap displayed compression followed by loss of cell integrity and the appearance of a protuberance prior to radicle protrusion. Conclusions: Coffee seed germination is the result of isodiametric growth of the embryo followed by elongation, at the expense of integrity of endosperm cap cells. The cell cycle, including cell division, is initiated prior to radicle protrusion. ABA inhibits expansion of the embryo, and hence subsequent events, including germination. Key words: Abscisic acid, ß-tubulin, Coffea arabica, coffee seed, cell morphology, germination, microtubules
Mechanism and control of Solanum lycocarpum
Pinto, L.V.A. ; Silva, E.A.A. Da; Davide, A.C. ; Mendes de Jesus, V.A. ; Toorop, P.E. ; Hilhorst, H.W.M. - \ 2007
Annals of Botany 100 (2007)6. - ISSN 0305-7364 - p. 1175 - 1187.
cell-wall extensibility - beta-mannanase activity - abscisic-acid - tomato seeds - micropylar endosperm - radicle emergence - embryo - expression - growth - gibberellin
Background Solanaceae seed morphology and physiology have been widely studied but mainly in domesticated crops. The present study aimed to compare the seed morphology and the physiology of germination of Solanum lycocarpum, an important species native to the Brazilian Cerrado, with two species with endospermic seeds, tomato and coffee. Methods Morphological parameters of fruits and seeds were determined by microscopy. Germination was monitored for 40 d under different temperature regimes. Endosperm digestion and resistance, with endo-beta-mannanase activity and required force to puncture the endosperm cap as respective markers, were measured during germination in water and in abscisic acid. Key Results Fruits of S. lycocarpum contain dormant seeds before natural dispersion. The best germination condition found was a 12-h alternating light/dark and high/low (20/30 degrees C) temperature cycle, which seemed to target properties of the endosperm cap. The endosperm cap contains 7-8 layers of elongated polygonal cells and is predestined to facilitate radicle protrusion. The force required to puncture the endosperm cap decreased in two stages during germination and showed a significant negative correlation with endo-beta-mannanase activity. As a result of the thick endosperm cap, the puncture force was significantly higher in S. lycocarpum than in tomato and coffee. Endo-beta-mannanase activity was detected in the endosperm cap prior to radicle protrusion. Abscisic acid inhibited germination, increase of embryo weight during imbibition, the second stage of weakening of the endosperm cap and of endo-beta-mannanase activity in the endosperm cap. Conclusions The germination mechanism of S. lycocarpum bears resemblance to that of tomato and coffee seeds. However, quantitative differences were observed in embryo pressure potential, endo-beta-mannanase activity and endosperm cap resistance that were related to germination rates across the three species.
Targeted transcript mapping for agronomic traits in potato
Fernandez del Carmen, M.A. ; Celis-Gamboa, C. ; Visser, R.G.F. ; Bachem, C.W.B. - \ 2007
Journal of Experimental Botany 58 (2007)11. - ISSN 0022-0957 - p. 2761 - 2774.
differential gene-expression - kaurenoic acid oxidase - tuber development - solanum-tuberosum - phytochrome-b - late blight - 20-oxidase gene - linkage maps - in-vitro - gibberellin
A combination of cDNA-amplified fragment length polymorphism (AFLP) and bulked segregant analysis (BSA) was used to identify genes co-segregating with earliness of tuberization in a diploid potato population. This approach identified 37 transcript-derived fragments with a polymorphic segregation pattern between early and late tuberizing bulks. Most of the identified transcripts mapped to chromosomes 5 (19 markers) and 12 (eight markers) of the paternal map. Quantitative trait locus (QTL) mapping of tuberization time also identified earliness QTLs on these two chromosomes. A potato bacterial artificial chromosome (BAC) library was screened with four of the markers linked to the main QTL. BAC contigs containing the markers showing the highest association with the trait have been identified. One of these contigs has been anchored to chromosome 5 on an ultradense genetic map of potato, which could be used as a starting point for map-based cloning of genes associated with earliness.
Gene expression programs during Brassica oleracea seed maturation, osmopriming and germination process and the stress tolerance level
Soeda, Y. ; Konings, M.C.J.M. ; Vorst, O.F.J. ; Houwelingen, A.M.M.L. van; Stoopen, G.M. ; Maliepaard, C.A. ; Kodde, J. ; Bino, R.J. ; Groot, S.P.C. ; Geest, A.H.M. van der - \ 2005
Plant Physiology 137 (2005)1. - ISSN 0032-0889 - p. 354 - 368.
zaadkieming - genexpressie - brassica oleracea - seed germination - gene expression - brassica oleracea - heat-shock proteins - arabidopsis-thaliana - tomato seeds - lea proteins - dormancy - accumulation - beta-1,3-glucanase - replication - gibberellin - performance
During seed maturation and germination, major changes in physiological status, gene expression, and metabolic events take place. Using chlorophyll sorting, osmopriming, and different drying regimes, Brassica oleracea seed lots of different maturity, stress tolerance, and germination behavior were created. Through careful physiological analysis of these seed lots combined with gene expression analysis using a dedicated cDNA microarray, gene expression could be correlated to physiological processes that occurred within the seeds. In addition, gene expression was studied during early stages of seed germination, prior to radicle emergence, since very little detailed information of gene expression during this process is available. During seed maturation expression of many known seed maturation genes, such as late-embryogenesis abundant or storage-compound genes, was high. Notably, a small but distinct subgroup of the maturation genes was found to correlate to seed stress tolerance in osmoprimed and dried seeds. Expression of these genes rapidly declined during priming and/or germination in water. The majority of the genes on the microarray were up-regulated during osmopriming and during germination on water, confirming the hypothesis that during osmopriming, germination-related processes are initiated. Finally, a large group of genes was up-regulated during germination on water, but not during osmopriming. These represent genes that are specific to germination in water. Germination-related gene expression was found to be partially reversible by physiological treatments such as slow drying of osmoprimed seeds. This correlated to the ability of seeds to withstand stress
Comparing potato tuberization and sprouting: opposite phenomena
Vreugdenhil, D. - \ 2004
American Journal of Potato Research 81 (2004)4. - ISSN 1099-209X - p. 275 - 280.
solanum-tuberosum-l - gene-expression - developmental-changes - hexose-phosphate - abscisic-acid - dormancy - conversion - enzymes - sucrose - gibberellin
The regulation of tuber formation and tuber sprouting are compared. As a starting point it is hypothesized that these two phenomena are opposite to each other. This idea is tested from three points of view: hormonal regulation, gene expression, and carbohydrate metabolism. It is concluded that there is only limited evidence to support the hypothesis. On the contrary, several examples are given indicating that similar mechanisms might be operative during tuber formation and tuber sprouting.
Changes in the sensitivity of parasitic weed seeds to germination stimulants
Matusova, R. ; Mourik, T.A. van; Bouwmeester, H.J. - \ 2004
Seed Science Research 14 (2004)4. - ISSN 0960-2585 - p. 335 - 344.
seasonal dormancy patterns - sisymbrium-officinale - arabidopsis-thaliana - ethylene biosynthesis - striga-hermonthica - orobanche-minor - gibberellin - temperature - light - broomrape
The effects of preconditioning temperature and preconditioning period on the sensitivity of parasitic weed seeds to the synthetic germination stimulant GR24 were studied under laboratory and field conditions. The temperature during preconditioning of Orobanche cumana and Striga hermonthica seeds strongly affected the responsiveness of the seeds to the applied germination stimulant. Preconditioning at an optimal temperature (21degreesC for O. cumana and 30degreesC for S. hermonthica) rapidly released dormancy and increased the sensitivity to GR24 by several orders of magnitude. After reaching maximum sensitivity, prolonged preconditioning rapidly induced secondary dormancy, i.e. decreased sensitivity of O. cumana and S. hermonthica to GR24. The rapid change in sensitivity of preconditioned seeds to germination stimulants during prolonged preconditioning was particularly visible at low concentrations of GR24. GR24 at higher concentrations (0.1 and 1 mg l(-1)) usually induced high germination of both species, regardless of the preconditioning period. The striking similarities between the response of parasitic weed seeds to GR24, described here, and results in the literature on non-parasitic wild plant seeds are discussed. Our results show that parasitic weed seeds are highly sensitive to the germination stimulant for a short period of time only, and then enter into secondary dormancy relatively quickly. The similar germination pattern of S. hermonthica seeds preconditioned for prolonged periods of time under laboratory and field conditions suggests that the mechanism observed is of ecological significance.
Analysis of natural allelic variation at seed dormancy loci of Arabidopsis thaliana
Alonso-Blanco, C. ; Bentsink, L. ; Hanhart, C.J. ; Vries, M.H.C. de; Koornneef, M. - \ 2003
Genetics 164 (2003)2. - ISSN 0016-6731 - p. 711 - 729.
quantitative trait loci - flowering time - abscisic-acid - l heynh - linkage map - germination - mutants - gibberellin - gene - light
Arabidopsis accessions differ largely in their seed dormancy behavior. To understand the genetic basis of this intraspecific variation we analyzed two accessions: the laboratory strain Landsberg erecta (Ler) with low dormancy and the strong-dormancy accession Cape Verde Islands (Cvi). We used a quantitative trait loci (QTL) mapping approach to identify loci affecting the after-ripening requirement measured as the number of days of seed dry storage required to reach 50% germination. Thus, seven QTL were identified and named delay of germination (DOG) 1-7. To confirm and characterize these loci, we developed 12 near-isogenic lines carrying single and double Cvi introgression fragments in a Ler genetic background. The analysis of these lines for germination in water confirmed four QTL (DOG1, DOG2, DOG3, and DOG6) as showing large additive effects in Ler background. In addition, it was found that DOG1 and DOG3 genetically interact, the strong dormancy determined by DOG1-Cvi alleles depending on DOG-3-Ler alleles. These genotypes were further characterized for seed dormancy/germination behavior in five other test conditions, including seed coat removal, gibberellins, and an abscisic acid biosynthesis inhibitor. The role of the Ler/Cvi allelic variation in affecting dormancy is discussed in the context of current knowledge of Arabidopsis germination.