Project description:ISD-starch (initiation, synthesis, and degradation): an integrated approach toward the understanding of starch metabolism and formation in plants
Project description:isd-starch-Initiation synthesis and degradation : an integrated approach toward the understanding of starch metabolism and formation in plants
Project description:● Adjustment to energy starvation is crucial to ensure growth and survival. In Arabidopsis thaliana (Arabidopsis), this process relies in part on the phosphorylation of the circadian clock regulator bZIP63 by SnRK1, a key mediator of responses to low energy. ● We investigated the effects of mutations in bZIP63 on plant carbon (C) metabolism and growth. Results from phenotypic, transcriptomic, and metabolomic analysis of bZIP63 mutants prompted us to investigate the starch accumulation pattern and the expression of genes involved in starch degradation and in the circadian oscillator. ● In order to get some clues about the role of transcription factor bZIP type bZIP63 in growth and development, we performed a comparative gene expression analysis of bzip63-2 mutant and wild type Ws, harvested at the end of night (EN = ZT 24), immediately before the onset of the light, to maximize the discovery of genes misregulated in bzip63-2. The resulting gene expression profiles revealed 230 upregulated and 117 downregulated genes in bzip63-2 compared to Ws. ● bZIP63 mutation impairs growth under light-dark cycles, but not under constant light. The reduced growth likely results from the accentuated C depletion towards the end of the night, which is caused by the accelerated starch degradation of bZIP63 mutants. The diel expression pattern of bZIP63 is dictated by both the circadian clock and energy levels, which could determine the changes in the circadian expression of clock and starch metabolic genes observed in bZIP63 mutants. ● We conclude that bZIP63 composes a regulatory interface between the metabolic and circadian control of starch breakdown to optimize C usage and plant growth.
Project description:When grown under phosphate (Pi) deficiency, plants adjust their developmental program and metabolic activity to cope with this nutritional stress. For Arabidopsis, the developmental responses include inhibition of primary root growth and enhanced formation of lateral roots and root hairs. Pi deficiency also inhibits photosynthesis by suppressing the expression of photosynthetic genes. Interestingly, early studies showed that photosynthetic gene expression was also suppressed in roots, a non-photosynthetic tissue. The biological relevance of this phenomenon, however, is not known. In this work, we characterized an Arabidopsis mutant, hps7, which is hypersensitive to Pi deficiency; the hypersensitivity includes an increased inhibition of root growth. HPS7 encodes a tyrosylprotein sulfotransferase (TPST). Accumulation of TPST proteins, but not mRNA, is induced by Pi deficiency. Comparative RNA-Seq analyses indicated that expression of many photosynthetic genes was activated in the roots of hps7. Under Pi deficiency, the expression of the photosynthetic genes in hps7 is further increased, which leads to the enhanced accumulation of chlorophyll, starch, and reactive oxygen species. The increased inhibition of root growth in hps7 under Pi deficiency was completely reversed by growing plants in the dark. Based on these results, we propose that suppression of photosynthetic gene expression in roots is required for sustained root growth under Pi deficiency.