Project description:The hormones gibberellins (GA) control many aspects of plant growth and development thruough the whole life cycle of the plant. For instance, GA participate in the establishment of the skotomorphogenic developmental program that is triggered when seeds germinate in darkness, i.e. under the soil. Under these conditions seedlings appear etiolated and developmental features usually triggered by light are kept repressed. The GA signaling elements GAI and RGA have a major, partially redundant role in this process. These proteins belong to the DELLA family of transcriptional regulators and are destabilized by GA, acting as negative regulators of the pathway. In order to understand the molecular basis of the regulation of the skotomorphogenesis by GA, we sought to identify early target genes of the activity of GAI in etiolated seedlings. For that purpose we analyzed rapid, global changes in gene expression in response to a transient accummulation of a dominant version of GAI, gai-1, which is resistant to GA-induced destabilization.
Project description:Ovule development is a key process for plant reproduction that ensures correct seed production. Understanding the molecular mechanisms that control ovule formation will also provide new approaches to increase crop yield for breeding. Several molecular factors and plant hormones, including gibberellins, are involved in ovule initiation and development. Gibberellins control ovule development by the destabilization of DELLA proteins, whereas DELLA activity has been proved to act as a positive factor for ovule primordia emergence. But the molecular mechanism by which DELLA act remained unknown. Here we have proved that DELLA proteins control ovule initiation by the formation of a protein complex with the CUC2 transcription factor. The DELLA protein GAI requires CUC2 to promote ovule primordia formation, thus GAI would function by its direct protein-protein interaction with CUC2 in cells of the placenta that determine the boundary regions between ovules during pistil development. Analysis of GAI-CUC2 interaction and colocalization in placenta support this hypothesis. Moreover, molecular analysis of the loci at which GAI protein may act as transcriptional co-regulators in a CUC2-dependent manner identified a subset of target genes that would be regulated by the GAI-CUC2 complex and contribute to regulate ovule primordia emergence.
Project description:The hormones gibberellins (GA) control many aspects of plant growth and development thruough the whole life cycle of the plant. For instance, GA participate in the establishment of the skotomorphogenic developmental program that is triggered when seeds germinate in darkness, i.e. under the soil. Under these conditions seedlings appear etiolated and developmental features usually triggered by light are kept repressed. The GA signaling elements GAI and RGA have a major, partially redundant role in this process. These proteins belong to the DELLA family of transcriptional regulators and are destabilized by GA, acting as negative regulators of the pathway. In order to understand the molecular basis of the regulation of the skotomorphogenesis by GA, we sought to identify early target genes of the activity of GAI in etiolated seedlings. For that purpose we analyzed rapid, global changes in gene expression in response to a transient accummulation of a dominant version of GAI, gai-1, which is resistant to GA-induced destabilization. Experiments were performed using wild type Col-0 and the transgenic line HS:gai-1 that expresses the dominant version gai-1 under the control of the promoter of the HSP18.2 gene, which is highly and rapidly induced at 37ºC. Three biological repeats were performed, and wild type and transgenic samples were labelled with Cy3 and Cy5, respectively. For each point in the time course (0, 1, 2 and 4h after a 30 minute treatment at 37ºC), a sample from the transgenic line was compared to the corresponding wild type control.
Project description:To understand how GA functions in regulating embryo development, a genome-wide transcriptomic analysis was carried out using 9DAF seeds dissected from siliques of dellaq (rga28 gai rgl1 rgl2) and the wild-type (col-0-2) grown in full-spectrum white fluorescent light at 22°C under long day conditions (16 h light/8 h dark). Then we found that GA regulates embryo development via DELLA-LEC1interaction, a subsequent genome-wide transcriptomic analysis was carried out using 9DAF seeds dissected from siliques of lec1-4 and the wild-type (col-0-1) in the same growth condition. Basing on the criteria of 1.5-fold cutoff for the genes with 5% false discovery rate, we first identified the differentially expressed genes in dellaq vs col-0-2, lec1-4 vs Col-0-1 subsets, which are referred to as DELLA and LEC1 regulated genes. These data reveal that DELLAs and LEC1 co-target a set of common genes in late embryogenesis, strongly supporting the role of DELLA-LEC1 in embryo development.
Project description:Upon illumination, etiolated seedlings experience a transition from heterotrophic to photoautotrophic growth. During this process, the tetrapyrrole biosynthesis pathway provides chlorophyll for photosynthesis. This pathway has to be tightly controlled to prevent the accumulation of photoreactive metabolites and to provide stoichiometric amounts of chlorophyll for its incorporation into photosynthetic protein complexes. Therefore, plants have evolved regulatory mechanisms to synchronize the biosynthesis of chlorophyll and chlorophyll-binding proteins. Two phytochrome-interacting factors (PIF1 and PIF3) and the DELLA proteins, which are controlled by the gibberellin pathway, are key regulators of this process. Here, we show that impairment of TARGET OF RAPAMYCIN (TOR) activity in Arabidopsis (Arabidopsis thaliana), either by mutation of the TOR complex component RAPTOR1B or by treatment with TOR inhibitors, leads to a significantly reduced accumulation of the photoreactive chlorophyll precursor protochlorophyllide in darkness but an increased greening rate of etiolated seedlings after exposure to light. Detailed profiling of metabolic, transcriptomic, and physiological parameters revealed that the TOR-repressed lines not only grow slower, they grow in a nutrient-saving mode, which allows them to resist longer periods of low nutrient availability. Our results also indicated that RAPTOR1B acts upstream of the gibberellin-DELLA pathway and its mutation complements the repressed greening phenotype of pif1 and pif3 after etiolation.