ABSTRACT
Gibberellins (GA) are key positive regulators of seed germination. Although the GA effects on seed germination have been studied in a number of species, little is known about the transcriptional reprogramming modulated by GA during this phase in species other than Arabidopsis thaliana. Here we report the transcriptome analysis of soybean embryonic axes during germination in the presence of paclobutrazol (PBZ), a GA biosynthesis inhibitor. We found a number of differentially expressed cell wall metabolism genes, supporting their roles in cell expansion during germination. Several genes involved in the biosynthesis and signaling of other phytohormones were also modulated, indicating an intensive hormonal crosstalk at the embryonic axis. We have also found 26 photosynthesis genes that are up-regulated by PBZ at 24 hours after imbibition (HAI) and down-regulated at 36 HAI, which led us to suggest that this is part of a strategy to implement an autotrophic growth program in the absence of GA-driven mobilization of reserves. Finally, 30 transcription factors (mostly from the MYB, bHLH, and bZIP families) were down-regulated by PBZ and are likely downstream GA targets that will drive transcriptional changes during germination.
Subject(s)
Gene Expression Regulation, Plant/drug effects , Germination/drug effects , Gibberellins/antagonists & inhibitors , Glycine max/genetics , Triazoles/pharmacology , Arabidopsis/genetics , Arabidopsis/metabolism , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Gibberellins/metabolism , Photosynthesis/drug effects , Plant Growth Regulators/antagonists & inhibitors , Plant Growth Regulators/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Seeds/genetics , Seeds/growth & development , Seeds/metabolism , Glycine max/growth & development , Glycine max/metabolism , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
The relationship between the phytohormones, gibberellin (GA) and abscisic acid (ABA) and light and temperature on seed germination is still not well understood. We aimed to investigate the role of the ABA and GA on seed germination of Vellozia caruncularis, V. intermedia and V. alutacea in response to light/dark conditions on different temperature. Seeds were incubated in GA (GA3 or GA4 ) or ABA and their respective biosynthesis inhibitors (paclobutrazol - PAC, and fluridone - FLU) solutions at two contrasting temperatures (25 and 40 °C). Furthermore, endogenous concentrations of active GAs and those of ABA were measured in seeds of V. intermedia and V. alutacea during imbibition/germination. Exogenous ABA inhibited the germination of Vellozia species under all conditions tested. GA, FLU and FLU + GA3 stimulated germination in the dark at 25 °C (GA4 being more effective than GA3 ). PAC reduced seed germination in V. caruncularis and V. alutacea, but did not affect germination of V. intermedia at 40 °C either under light or dark conditions. During imbibition in the dark, levels of active GAs decreased in the seeds of V. intermedia, but were not altered in those of V. alutacea. Incubation at 40 °C decreased ABA levels during imbibition in both V. caruncularis and V. alutacea. We conclude that the seeds of Vellozia species studied here require light or high temperature to germinate and ABA has a major role in the regulation of Vellozia seed germination in response to light and temperature.
Subject(s)
Abscisic Acid/pharmacology , Gene Expression Regulation, Plant , Germination/drug effects , Gibberellins/pharmacology , Magnoliopsida/drug effects , Plant Growth Regulators/pharmacology , Abscisic Acid/antagonists & inhibitors , Darkness , Gibberellins/antagonists & inhibitors , Hot Temperature , Light , Magnoliopsida/physiology , Magnoliopsida/radiation effects , Plant Growth Regulators/antagonists & inhibitors , Pyridones/pharmacology , Seeds/drug effects , Seeds/physiology , Seeds/radiation effects , Triazoles/pharmacologyABSTRACT
Annona mucosa é uma árvore frutífera da família Annonaceae, produtora de importantes metabólitos secundários de interesse medicinal, como lignanas, acetogeninas e alcaloides. A cultura in vitro de calos representa um importante recurso para a produção contínua de metabólitos, viabilizando a conservação da biodiversidade química e a obtenção controlada de material para estudos biológicos e fitoquímicos. O objetivo deste trabalho foi otimizar a produção de calos friáveis de A. mucosa, avaliando o efeito de diferentes meios nutritivos e fitorreguladores. Segmentos de folha e de hipocótilo de plântulas germinadas in vivo foram utilizados como explantes e inoculados nos meios de cultura MS, WPM e B5 suplementados com picloram (2 - 20µM) isolado ou combinado com as citocininas BAP, KIN ou TDZ (0,2 - 1µM). As culturas foram mantidas a 26±2ºC, no escuro, com subcultivos mensais. A produção de calos foi avaliada por aferição do peso dos calos, após 90 dias. Em todos os tratamentos na presença da auxina picloram, o cultivo de hipocótilos resultou em maior porcentagem de formação de calos, sobretudo no meio de cultura WPM. A associação com TDZ produziu massa calogênica friável altamente proliferativa e ausente de oxidação, alcançando valores superiores àqueles obtidos em trabalhos prévios com a espécie. Os resultados viabilizam o uso do material em suspensões celulares e posterior caracterização fitoquímica para a exploração da produção in vitro de metabólitos da espécie.
The Annona mucosa is a fruit tree of the Annonaceae family that produces a range of secondary metabolites of medicinal interest, such as lignans, acetogenins and alkaloids. The callus culture represents a renewable source of valuable medicinal compounds and controlled supply of material for biological and phytochemical studies. Therefore, this study was carried out to investigate the effects of three nutrient media, different concentrations of picloram and cytokinin types, in order to optimize the biomass yield and friability of calluses of A. mucosa. Leaf and hypocotyl segments from seedlings produced from in vivo seed germination were used as explants, which were inoculated in MS, WPM and B5 culture media supplemented with picloram (2-20µM) only or in addition to the cytokinins BAP, KIN or TDZ (0,2 - 1µM ). Cultures were maintained at 26±2ºC in the dark, with monthly subcultures. After 90 days, biomass production was evaluated. In all treatments, hypocotyl explants provided the highest percentage of callus formation, particularly in WPM. The association with TDZ produced highly proliferative friable callus, with no oxidation, reaching higher values than the previous works with this species. The results enable the use of the calluses produced in cell suspensions and the subsequent phytochemical characterization, in order to explore the in vitro production of metabolites of the species.
Subject(s)
Plants, Medicinal/classification , Annona/anatomy & histology , Plant Growth Regulators/antagonists & inhibitors , In Vitro Techniques/instrumentation , Culture Media/analysisABSTRACT
The present study was designed to establish the role of an essential hormone controlling sex expression in cucumber. A potent anti-ethylene agent, AgNO3, completely inhibited pistillate flower formation caused by IAA, ACC or ethephon. Inhibitors of ethylene biosynthesis, AVG and CoCl2 also suppressed feminization due to exogenous IAA or ACC. Though AVG also suppressed ethephon-induced feminization, this may be due to the second effect of AVG rather than the effect on ACC biosynthesis. These results confirm that ethylene is a major factor regulating feminization and that exogenous auxin induces pistillate flower formation through its stimulation of ethylene production, rather than ACC production.