Project description:We examined the changes in gene expression in Arabidopsis thaliana grown under arsenate stress. The transcriptional profiling reveals antioxidant activity and repression of the phosphate starvation response. Keywords: dual label, stress response
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.
Project description:Inorganic phosphate (Pi) is an essential nutrient, which is often served as a limiting factor in plant growth. It has been reported that SPL family members, such as SPL3, regulate Pi deficiency responses by controlling the expression of Pi deficiency responsive genes. To elucidate whether SPL9 respond to low phosphorus stress, we investigated the phenotypes and conduct RNA sequencing analysis in transgenic Arabidopsis thaliana with overexpressing SPL9 (R9) under conditions of both normal and low Pi availability. Compared with wild-type plants, R9 showed decreased anthocyanin accumulation and increased Pi contents in shoots under Pi deficiency. Through RNA-seq analysis compared with wild-type plants, we detected 217 genes significantly differentially expressed in conditions of Pi sufficiency, and 121 genes differentially expressed in conditions of Pi deficiency in R9 plants. Under Pi deficiency, these genes included multiple protein kinases, jasmonic acid response genes and genes related to salt stress responses. Genes associated with hydrolase and transferase activity were also differentially regulated by Pi deficiency, such as cytochrome P450 monooxygenases. Of particular note, the transcription factor AP2-EREBP and members of the bHLH family were among the most significantly differentially regulated genes identified under both Pi sufficient and Pi deficient conditions.
Project description:Background: The UK horticultural and agricultural industries routinely apply large amounts of inorganic fertiliser to maintain crop yield and quality, since chemical assays of soil nutrients are unreliable. Excessive fertiliser applications are costly and can lead to unnecessary pollution. A possible solution is to use sensor (GM or non-GM) technologies that exploit the changes in plant gene expression under incipient nutrient deficiency. Aim: The aim of this project is to use mutants with reduced leaf phosphate contents to identify genes upregulated in response to phosphate stress. Preliminary gene expression analysis has identified several phosphate responsive genes to be upregulated in the pho1 mutant. However, further replicates of the experiment are required to confirm these changes. Methods: Arabidopsis mutant pho1 (N8507) and its parent ecotype Columbia 2 (N907) will be grown on MS agar under identical conditions. RNA will be extracted from the rosette leaves of both parent and mutant and the same growth stage. By comparing the expression profiles, we will be able to differentiate between genes that are upregulated in leaves experiencing phosphate stress. Previously, two GeneChips have been used (mutant and parent) to provide preliminary data. A further two biological replicates are now required to confirm these results. Promoters and transcripts of these genes will underpin the development of novel sensor technologies, and knowledge of the gene expression profiles will improve our understanding of the physiology of plant mineral nutrition.