Differential transcriptome modulation leads to variation in arsenic stress response in Arabidopsis thaliana accessions.

Arsenic (As) is a ubiquitous metalloid and a health hazard to millions of people worldwide. The presence of As in groundwater poses a threat as it not only affects crop productivity but also contaminates food chain. Therefore, it is essential to understand molecular mechanisms underlying uptake, transport and accumulation of As in plants. In recent past, natural variation in Arabidopsis thaliana has been utilized to understand molecular and genetic adaptation under different stresses. In this study, responses of Arabidopsis accessions were analyzed at biochemical and molecular levels towards arsenate [As(V)] stress. On the basis of reduction in root length, accessions were categorized into tolerant and sensitive ones towards As(V). Root length analysis led to the identification of Col-0 (<10% reduction) and Slavi-1 (>60% reduction) as the most tolerant and sensitive accessions, respectively. Comparative genome-wide expression analysis revealed differential expression of 168 and 548 genes in Col-0 and Slavi-1, respectively, with 120 common differentially expressed genes. A number of genes associated with defense and stress-response, transport system, regulatory mechanisms and biochemical processes showed differential expression in contrasting accessions. The study provides an insight into the molecular mechanisms associated with stress response and processes involved in adaptation strategies towards As stress.

Differential sulphur assimilation mechanism regulates response of Arabidopsis thaliana natural variation towards arsenic stress under limiting sulphur condition.

Arsenic (As) is a ubiquitous element, which imposes threat to crops productivity and human health through contaminated food chain. As a part of detoxification mechanism, As is chelated and sequestered into the vacuoles via sulphur containing compounds glutathione (GSH) and phytochelatins (PCs). Under limiting sulphur (LS) conditions, exposure of As leads to enhanced toxic effects in plants. Therefore, it is a prerequisite to understand molecular mechanisms involved in As stress response under sulphur deficiency conditions in plants. In recent years, natural variation has been utilized to explore the genetic determinants linked to plant development and stress response. In this study, natural variation in Arabidopsis has been utilized to understand the molecular mechanisms underlying LS and As(III) stress response. Analysis of different accession of Arabidopsis led to the identification of Koz2-2 and Ri-0 as the most tolerant and sensitive accessions, respectively, towards As(III) and LS+As(III) stress. Biochemical analysis and expression profiling of the genes responsible for sulphur transport and assimilation as well as metal detoxification and accumulation revealed significantly enhanced sulphur assimilation mechanism in Koz2-2 as compared to Ri-0. Analyses suggest that genetic variation regulates differential response of accessions towards As(III) under LS condition.

Natural variations in expression of regulatory and detoxification related genes under limiting phosphate and arsenate stress in Arabidopsis thaliana.

Abiotic stress including nutrient deficiency and heavy metal toxicity severely affects plant growth, development, and productivity. Genetic variations within and in between species are one of the important factors in establishing interactions and responses of plants with the environment. In the recent past, natural variations in Arabidopsis thaliana have been used to understand plant development and response toward different stresses at genetic level. Phosphorus deficiency negatively affects plant growth and metabolism and modulates expression of the genes involved in Pi homeostasis. Arsenate, As(V), a chemical analog of Pi, is taken up by the plants via phosphate transport system. Studies suggest that during Pi deficiency, enhanced As(V) uptake leads to increased toxicity in plants. Here, the natural variations in Arabidopsis have been utilized to study the As(V) stress response under limiting Pi condition. The primary root length was compared to identify differential response of three Arabidopsis accessions (Col-0, Sij-1, and Slavi-1) under limiting Pi and As(V) stress. To study the molecular mechanisms responsible for the differential response, comprehensive expression profiling of the genes involved in uptake, detoxification, and regulatory mechanisms was carried out. Analysis suggests genetic variation-dependent regulatory mechanisms may affect differential response of Arabidopsis natural variants toward As(V) stress under limiting Pi condition. Therefore, it is hypothesized that detailed analysis of the natural variations under multiple stress conditions might help in the better understanding of the biological processes involved in stress tolerance and adaptation.