Genome–wide transcriptional response of contrasting genotypes of industrial crop castor to As(V) stress: Identification of genes and mechanisms associated with As(V) tolerance

Abstract

Arsenic (As) is toxic to living organisms at high concentrations. Utilization of an industrial non-edible oilseed crop like Ricinus communis L. (castor) for revegetation and phytoremediation of As–contaminated land can be highly beneficial. Although a lot of research has been conducted on castor, little is known about As toxicity and tolerance mechanisms in this bioenergy crop. In the present study, genome-wide transcriptional analysis was performed using RNA sequencing (RNA-Seq) to identify differentially expressed genes in As-tolerant and As-sensitive castor genotypes in response to As(V) treatment. RNA-Seq data showed a differential expression pattern for stress-related genes between WM (tolerant) and GCH 2 (sensitive) genotype in response to 200 μM As(V) treatment. A total of 19 DEGs (13 up and 6 downregulated) and 7157 DEGs (4093 up and 3064 downregulated) were identified in leaves of 200 µM As(V)-treated WM and GCH 2 genotypes, respectively. Expression of genes associated with metal transport such as ZIP1, ZIP4, ZIP5, NRAMP3, metal chelators (MT-2, MT-3, PCS, NAS), photosynthesis responsive genes corresponding to Chl a-b binding proteins, RuBisCO small subunit and protein low PSII accumulation 3 were downregulated in GCH 2 whereas expression of these genes were either maintained or upregulated in WM in response to 200 µM toxicity. Expression level of genes involved in As uptake and transport such as phosphate transporters, aquaporins, and mitochondrial dicarboxylate transporter (DIT1, DIT2.1) were upregulated in 200 µM As(V)-treated sensitive genotype GCH 2 but maintaind in WM.