Project description:Drought is an important environmental factor affecting plant growth and biomass production. Despite this importance, little is known on the molecular mechanisms regulating plant growth under water limiting conditions. The main goal of this work was to investigate, using a combination of growth and molecular profiling techniques, how Arabidopsis thaliana leaves adapt their growth to prolonged mild osmotic stress. Fully proliferating, expanding and mature leaves were harvested from plants grown on plates without (control) or with 25mM mannitol (osmotic stress) and compared to seedlings at stage 1.03.
Project description:Drought is an important environmental factor affecting plant growth and biomass production. Despite this importance, little is known on the molecular mechanisms regulating plant growth under water limiting conditions. The main goal of this work was to investigate, using a combination of growth and molecular profiling techniques, how Arabidopsis thaliana leaves adapt their growth to prolonged mild osmotic stress. Fully proliferating, expanding and mature leaves were harvested from plants grown on plates without (control) or with 25mM mannitol (osmotic stress) and compared to seedlings at stage 1.03. Total RNAs were extracted using Trizol method from vegetative part of seedlings at stage 1.03 and leaves that are fully proliferating, expanding or mature. All plants were grown in vitro on medium without (0mM) or with mannitol (25mM) in three independent biological experiments. Each sample was pooled from multiple plants and multiple plates in one experiment. RNA samples were submitted to ATH1 array hybridization.
Project description:Leaf growth is a complex developmental process that is continuously fine-tuned by the environment. Various abiotic stresses, including mild drought stress, have been shown to inhibit leaf growth in Arabidopsis thaliana (Arabidopsis), but the underlying mechanisms remain largely unknown. Here we identify the redundant Arabidopsis transcription factors ETHYLENE RESPONSE FACTOR 5 (ERF5) and ERF6 as master regulators which adapt leaf growth to environmental changes. ERF5 and ERF6 gene expression is induced very rapidly and specifically in actively growing leaves after sudden exposure to osmotic stress that mimics mild drought. Subsequently, enhanced ERF6 expression inhibits cell proliferation and leaf growth by a process involving GA and DELLA signaling. Using an ERF6 inducible overexpression line, we demonstrate that the GA-degrading enzyme GA2-OX6 is transcriptionally induced by ERF6 and that consequently DELLA proteins are stabilized. As a result, ERF6 gain-of-function lines are dwarfed and hypersensitive to osmotic stress, while growth of erf5erf6 loss-of-function mutants is less affected by stress. Next to its role in plant growth under stress, ERF6 also activates the expression of a plethora of osmotic stress-responsive genes, including the well-known stress tolerance genes STZ, MYB51 and WRKY33. Interestingly, the activation of the stress tolerance genes by ERF6 occurs independently from the ERF6-mediated growth inhibition. Together, these data fit into a leaf growth regulatory model in which ERF5 and ERF6 form a missing link between the previously observed stress-induced 1-aminocyclopropane-1-carboxylic acid (ACC) accumulation and DELLA-mediated cell cycle exit and execute a dual role by regulating both stress tolerance and growth-inhibition.
Project description:Genome-wide transcriptome analysis of Arabidopsis thaliana was performed to understand the role of auxin in the response of leaf growth to osmotic stress. We studied transcriptional changes in proliferating leaves of the seedlings grown in vitro on control medium, medium supplemented with 25mM mannitol, 0.1μM NAA and 0.1μM NAA + 25mM mannitol.
Project description:Leaf growth is a complex developmental process that is continuously fine-tuned by the environment. Various abiotic stresses, including mild drought stress, have been shown to inhibit leaf growth in Arabidopsis thaliana (Arabidopsis), but the underlying mechanisms remain largely unknown. Here we identify the redundant Arabidopsis transcription factors ETHYLENE RESPONSE FACTOR 5 (ERF5) and ERF6 as master regulators which adapt leaf growth to environmental changes. ERF5 and ERF6 gene expression is induced very rapidly and specifically in actively growing leaves after sudden exposure to osmotic stress that mimics mild drought. Subsequently, enhanced ERF6 expression inhibits cell proliferation and leaf growth by a process involving GA and DELLA signaling. Using an ERF6 inducible overexpression line, we demonstrate that the GA-degrading enzyme GA2-OX6 is transcriptionally induced by ERF6 and that consequently DELLA proteins are stabilized. As a result, ERF6 gain-of-function lines are dwarfed and hypersensitive to osmotic stress, while growth of erf5erf6 loss-of-function mutants is less affected by stress. Next to its role in plant growth under stress, ERF6 also activates the expression of a plethora of osmotic stress-responsive genes, including the well-known stress tolerance genes STZ, MYB51 and WRKY33. Interestingly, the activation of the stress tolerance genes by ERF6 occurs independently from the ERF6-mediated growth inhibition. Together, these data fit into a leaf growth regulatory model in which ERF5 and ERF6 form a missing link between the previously observed stress-induced 1-aminocyclopropane-1-carboxylic acid (ACC) accumulation and DELLA-mediated cell cycle exit and execute a dual role by regulating both stress tolerance and growth-inhibition. Samples were obtained from three independent experiments and from multiple plates within the experiment. Whole seedlings were harvested rapidly in an excess of RNAlater® solution (Ambion), and after overnight storage at 4°C, dissected under a binocular microscope on a cooling plate with precision microscissors. Dissected leaves were transferred to a new tube, frozen in liquid nitrogen, and ground with a Retsch machine and 3-mm metal balls. RNA was extracted with TriZol (Invitrogen) and further purified with the RNeasy Mini Kit (Qiagen). DNA digestion was done on columns with RNase-free DNase I (Roche). For the identification of genome-wide expression changes, samples of the strong ERF6-overexpressing line (ERF6IOE-S) and the control line (GFP:IOE) were harvested 4 h after transfer to DEX. Two µg of pure RNA samples were hybridized to AGRONOMICS1 Arabidopsis Tiling Arrays (Rehrauer et al., 2010) at the VIB Microarray Facility (Leuven, Belgium).
Project description:Plant responses to abiotic stresses are accompanied by massive changes in transcriptome composition. To provide a comprehensive view of stress-induced changes in the Arabidopsis thaliana transcriptome, we have used whole-genome tiling arrays to analyze the effects of salt, osmotic, cold and heat stress as well as application of the hormone abscisic acid (ABA), an important mediator of stress responses.
Project description:Typically, when fully developed leaves of Arabidopsis thaliana are exposed to an increase in light intensity, they are able to increase their photosynthetic capacity in a process known as dynamic acclimation. Fully developed leaves of Arabidopsis thaliana were exposed to a fourfold increase in light intensity for 7 days to induce high light acclimation. This treatment was subjected to wild-type and a non-acclimating mutant lacking the gpt2 gene. The proteomic responses of the leaves were investigated using label-free mass spectrometry. A large reorganisation of the proteome was shown, with increases in the abundance of proteins of photosynthesis and carbon metabolism. Subtle differences were seen between the WT and gpt2 mutant: in the mutant, an increased stress response was seen, and some differences in the responses of metabolism. Proteomic responses generally correlated with physiological responses.