Project description:A great majority of plants synchronize flowering with day length. In rice, the most important environmental cue that triggers flowering is the photoperiod. Here, we show that the s73 mutant, identified in a gamma irradiated Bahia collection, displays early flowering and photoperiodic insensitivity due to a null mutation in the SE5 gene, which encodes an enzyme implicated in phytochrome chromophore biosynthesis. s73 mutant plants showed a number of alterations in the characteristic diurnal expression patterns of master genes involved in photoperiodic control of flowering, resulting in up-regulation of Hd3a, the most important floral integrator. Ehd1, an additional rice floral activator, was also highly expressed in the s73 mutant, suggesting that SE5 represses Ehd1 in wild-type plants. Silencing of Ehd1 in both Bahia and s73 backgrounds implies that SE5 regulates Ehd1 expression. The data also indicate that SE5 confers photoperiodic sensitivity through regulation of Hd1. These results provide direct evidence that phytochromes inhibit flowering affecting both Hd1 and Ehd1 flowering pathways.
Project description:A great majority of plants synchronize flowering with day length. In rice, the most important environmental cue that triggers flowering is the photoperiod. Here, we show that the s73 mutant, identified in a gamma irradiated Bahia collection, displays early flowering and photoperiodic insensitivity due to a null mutation in the SE5 gene, which encodes an enzyme implicated in phytochrome chromophore biosynthesis. s73 mutant plants showed a number of alterations in the characteristic diurnal expression patterns of master genes involved in photoperiodic control of flowering, resulting in up-regulation of Hd3a, the most important floral integrator. Ehd1, an additional rice floral activator, was also highly expressed in the s73 mutant, suggesting that SE5 represses Ehd1 in wild-type plants. Silencing of Ehd1 in both Bahia and s73 backgrounds implies that SE5 regulates Ehd1 expression. The data also indicate that SE5 confers photoperiodic sensitivity through regulation of Hd1. These results provide direct evidence that phytochromes inhibit flowering affecting both Hd1 and Ehd1 flowering pathways. Four biological replicates from each genotype (s73 mutant and Bahia wt) were labelled with Cy3 and Cy5 alternatively (2+2) following a dye-swap design. In total, 4 microarrays were hybridized. The supplementary file 'GSE16796_stat_analysis.txt' contains the final statistical analysis of study GSE16796.
Project description:Flowering of rice is triggered by transcriptional reprogramming at the shoot apical meristem (SAM) mediated by florigenic proteins produced in leaves in response to changes in the photoperiod. Florigens are more rapidly expressed under short day (SD) and include the HEADING DATE 3a (Hd3a) and RICE FLOWERING LOCUS T1 (RFT1) Phosphatidyl Ethanolamine Binding Proteins (PEBP). Hd3a and RFT1 are largely redundant at converting the SAM into an inflorescence, but whether they activate the same target genes and convey all photoperiodic information that modifies gene expression at the SAM is currently unclear. We uncoupled the contribution of Hd3a, RFT1 and SD to transcriptome reprogramming at the SAM, by RNA-sequencing of dex-inducible over-expressors of single florigens and wild type plants exposed to photoperiodic induction. Fifteen highly differentially expressed genes common to Hd3a, RFT1 and SD were retrieved, ten of which still uncharacterized. Detailed functional studies on some candidates revealed a role for LOC_Os04g13150 in determining tiller angle and bract development and the gene was renamed BROADER TILLER ANGLE 1 (BRT1). We identified a core set of genes common to florigenic and photoperiodic induction and defined the function of a novel florigen target controlling tiller angle.
Project description:Two aspects of light are very important for plant development: the length of the light phase or photoperiod and the quality of incoming light. Photoperiod detection allows plants to anticipate the arrival of the next season, whereas light quality, mainly the red to far-red ratio (R:FR), is an early signal of competition by neighbouring plants. phyB represses flowering by antagonising CO at the transcriptional and post-translational levels. A low R:FR decreases active phyB and consequently increases active CO, which in turn activates the expression of FT, the plant florigen. Other phytochromes like phyD and phyE seem to have redundant roles with phyB. PFT1, the MED25 subunit of the plant Mediator complex, has been proposed to act in the light-quality pathway that regulates flowering time downstream of phyB. However, whether PFT1 signals through CO and its specific mechanism are unclear. Here we show that CO-dependent and -independent mechanisms operate downstream of phyB, phyD and phyE to promote flowering, and that PFT1 is equally able to promote flowering by modulating both CO-dependent and -independent pathways. Our data are consistent with the role of PFT1 as an activator of CO transcription, and also of FT transcription, in a CO-independent manner. Our transcriptome analysis is also consistent with CO and FT genes being the most important flowering targets of PFT1. Furthermore, comparison of the pft1 transcriptome with transcriptomes after fungal and herbivore attack strongly suggests that PFT1 acts as a hub, integrating a variety of interdependent environmental stimuli, including light quality and jasmonic acid-dependent defences.
Project description:This study was performed to study the effect of silicon (Si) nutrition on suberization and lignification in roots of rice. Besides physiological and histochemical examinations of the roots, transcription of candidate genes related to synthesis of suberin and lignin was investigated using microarray analysis. 14 days old rice seedlings (Oryza sativa, cv. Selenio) were cultivated for 28 days in non-aerated nutrient solution (mM: 1.43 NH4NO3, 0.32 NaH2PO4 x H2O, 0.51 K2SO4, 1 CaCl2 x 2 H2O, 1.6 MgSO4 x 7 H2O; µM: 1.82 MnSO4, 0.03 (NH4)6Mo7O24, 9 H3BO3, 0.3 ZnSO4 x 7 H2O and 0.15 CuSO4). The pH-value was adjusted to 6.0 by addition of 10 % (v/v) H2SO4 and 0.75 M KOH.Plants were supplied with Si in form of K2SiO3 at concentrations 0 ppm Si (control) and 50 ppm Si (1.78 mM) and potassium in the control treatment was balanced with K2SO4 supply. The plants were grown in a growth chamber (photoperiod: 14 h light, 10 h dark; temperature 25°C day / 20°C night; relative humidity 75 %; light intensity 220 µmol m2 s-1). Adventitious roots were harvested at 0-2 cm and 4-6 cm distance from the root tip and frozen immediately in liquid nitrogen. For RNA isolation, roots were ground under liquid nitrogen and total RNA was isolated using TRIsure® Reagent (Bioline, Luckenwalde, Germany) following the instructions of the manufacturer. To examine transcription of genes related to suberin and lignin synthesis, a self developed microarray containing amongst others ABC transporter, aclytransferases, ß-ketoacyl-CoA synthases and peroxidases was used .
Project description:Two aspects of light are very important for plant development: the length of the light phase or photoperiod and the quality of incoming light. Photoperiod detection allows plants to anticipate the arrival of the next season, whereas light quality, mainly the red to far-red ratio (R:FR), is an early signal of competition by neighbouring plants. phyB represses flowering by antagonising CO at the transcriptional and post-translational levels. A low R:FR decreases active phyB and consequently increases active CO, which in turn activates the expression of FT, the plant florigen. Other phytochromes like phyD and phyE seem to have redundant roles with phyB. PFT1, the MED25 subunit of the plant Mediator complex, has been proposed to act in the light-quality pathway that regulates flowering time downstream of phyB. However, whether PFT1 signals through CO and its specific mechanism are unclear. Here we show that CO-dependent and -independent mechanisms operate downstream of phyB, phyD and phyE to promote flowering, and that PFT1 is equally able to promote flowering by modulating both CO-dependent and -independent pathways. Our data are consistent with the role of PFT1 as an activator of CO transcription, and also of FT transcription, in a CO-independent manner. Our transcriptome analysis is also consistent with CO and FT genes being the most important flowering targets of PFT1. Furthermore, comparison of the pft1 transcriptome with transcriptomes after fungal and herbivore attack strongly suggests that PFT1 acts as a hub, integrating a variety of interdependent environmental stimuli, including light quality and jasmonic acid-dependent defences. Two genotypes, WT (Columbia) and pft1-1 mutants. Three biological replicates for each condition (genotype X temperature combination). RNA prepared independently for each sample.
Project description:The plant circadian clock is linked to development on every scale, from control of the cell cycle to determination of flowering time. Of particular importance is the photoperiodic pathway, through which changes of day length (photoperiod) are interpreted. Circadian regulation of this pathway is generally studied in seedlings. This allows researchers to test the effect of different environmental conditions, such as extreme photoperiods or temperature, more rapidly than in adult plants. However, this approach fails to identify links between the photoperiodic pathway and other ageing-related processes, such as senescence. To close this knowledge gap, we collected data from Arabidopsis thaliana at two different timescales: the ‘flowering’ timescale and the ‘daily’ timescale. By shifting the photoperiod from short days (SD) to long days (LD), we induced flowering, via the photoperiodic pathway. We then sampled across 24h at 2, 7, and 12 days after this transition. We find that the regulation of senescence-associated genes begins soon after the transition from SD to LD. We explore how downstream targets of the circadian clock have changes in expression across the flowering timescale. Surprisingly, many genes shift from their time of peak expression, suggesting a widespread rewiring of the circadian clock’s targets during the flowering transition.
Project description:Chilling stress is a major abiotic stress that affects rice growth and development. Rice seedlings are quite sensitive to chilling stress and this harms global rice production. Comprehensive studies of the molecular mechanisms for response to low temperature are of fundamental importance to chilling tolerance improvement. The number of identified cold regulated genes (CORs) in rice is still very small. Circadian clock is an endogenous timer that enables plants to cope with forever changing surroundings including light–dark cycles imposed by the rotation of the planet. Previous studies have demonstrated that the circadian clock regulates stress tolerances in plants show circadian clock regulation of plant stress tolerances. However, little is known about coordination of the circadian clock in rice chilling tolerance. In this study, we investigated rice responses to chilling stress under conditions with natural light-dark cycles. We demonstrated that chilling stress occurring at nighttime significantly decreased chlorophyll content and photosynthesis efficiency in comparison with that occurring at daytime. Transcriptome analysis characterized novel CORs in indica rice, and suggested that circadian clock obviously interferes with cold effects on key genes in chlorophyll (Chl) biosynthesis pathway and photosynthesis-antenna proteins. Expression profiling revealed that chilling stress during different Zeitberger times (ZTs) at nighttime repressed the expression of those genes involved Chl biosynthesis and photosynthesis, whereas stress during ZTs at daytime increases their expression dramatically. Moreover, marker genes OsDREBs for chilling tolerance were regulated differentially by the chilling stress occurring at different ZTs. The phase and amplitude of oscillation curves of core clock component genes such as OsLHY and OsPRR1 are regulated by chilling stress, suggesting the role of chilling stress as an input signal to the rice circadian clock. Our work revealed impacts of circadian clock on chilling responses in rice, and proved that the effects on the fitness costs are varying with the time in a day when the chilling stress occurs.
Project description:This study aim to understand how the long and short day flowering pathways are integrated and the mechanism of photoperiod perception in rice. Trascriptome at different time points under LD and SD conditions reveal that photoperiodism in rice is controlled by the evening complex. Mutants in LUX ARRYTHMO (LUX) and EARLY FLOWERING3 (ELF3) orthologs abolish flowering. We show that light causes a rapid and sustained degradation of ELF3-1, and this response is dependent on phyB. ChIP-seq of ELF3 and LUX reveal that EC controls both LD and SD flowering pathways by directly binding and suppressing the expression of key floral repressors, including PRR7 orthologs and Ghd7.