Project description:In low rainfall regions soils are naturally conditioned with frequent co-occurrence of salinity and alkalinity. Plant salinity responses both at physiological and molecular level have been extensively researched. However, effects of the combined treatment of alkaline salinity that could greatly reduce plant growth and the mechanisms responsible for tolerance remain indeterminate. In Brassica juncea, large reductions in biomass and increased leaf Na+ concentration under alkaline salinity indicates that the combined treatment had greater negative effect than salinity on both growth and the physiological responses of the plant. To determine molecular mechanisms potentially controlling adaptive tolerance responses to salinity and alkaline salinity, the moderately tolerant genotype NDR 8501 was further investigated using microarray analysis. The transcripts of treated leaf tissues verses those of the untreated control sample were analysed after prolonged stress of four weeks. In total, 528 salinity responsive and 1245 alkaline salinity responsive genes were indentified and only 101 genes were expressed jointly in either of the two treatments. Transcription of 37% more genes involved in response to alkaline salinity than salinity alone, which suggests the increased impact and severity of the combined stress on the plant, indicating the transcription of a far greater number of genes likely involved in mitigation and damage control. Transcription of KUP2 and KUP7 genes involved in potassium homeostasis under salinity alone and NHX1 and ENH1 genes for ion (K+ and Na+) homeostasis under alkaline salinity, clearly demonstrated that different genes and genetic pathways are involved in response to each stress. They further provide supporting evidence for the physiological responses that occur in the plant, with massive reprogramming of the transcriptome leading to partial ion exclusion, shuttling and compartmentation. Salinity and alkaline salinity induced gene expression in Brassica juncea leaf was measured at 4 weeks of prolonged treatment of 50 mM NaCl alone and combined with 2.5 mM HCO3- versus non-stressed control. A single experiment was conducted using Brassica juncea genotype NDR 8501 at a single time point (fours weeks after treatment) with three replications per treatment.
Project description:Here, we employed high-throughput sequencing to identify microRNAs in CMS and its maintainer fertile (MF) lines of Brassica juncea. We identified 197 known and 78 new candidate microRNAs during reproductive development of B. juncea. A total of 47 differentially expressed microRNAs between CMS and its maintainer fertile lines were discovered, according to their sequencing read number.
Project description:Oilseed mustard, Brassica juncea, exhibits high levels of genetic variability for salinity tolerance. To obtain the global view of transcriptome and investigate the molecular basis of salinity tolerance in a salt-tolerant variety CS52 of B. juncea, we performed transcriptome sequencing of control and salt-stressed seedlings. De novo assembly of 184 million high-quality paired-end reads yielded 42,327 unique transcripts longer than 300 bp with RPKM ≥1. When compared with non-redundant proteins, we could annotate 67% unigenes obtained in our study. Based on the mapping to expressed sequence tags (ESTs), 52.6% unigenes are novel compared to EST data available for B. juncea and constituent genomes. Differential expression analysis revealed altered expression of 1469 unigenes in response to salinity stress. Of these, 587, mainly associated with ROS detoxification, sulfur assimilation and calcium signaling pathways, are up regulated. Notable of these is RSA1 (SHORT ROOT IN SALT MEDIUM 1) INTERACTING TRANSCRIPTION FACTOR 1 (RITF1) homolog up regulated by >100 folds in response to stress. RITF1, encoding a bHLH transcription factor, is a positive regulator of SOS1 and several key genes involved in scavenging of salt stress-induced reactive oxygen species (ROS). Further, we performed comparative expression profiling of key genes implicated in ion homeostasis and sequestration (SOS1, SOS2, SOS3, ENH1, NHX1), calcium sensing pathway (RITF1) and ROS detoxification in contrasting cultivars, B. juncea and B. nigra, for salinity tolerance. The results revealed higher transcript accumulation of most of these genes in B. juncea var. CS52 compared to salt-sensitive cultivar even under normal growth conditions. Together, these findings reveal key pathways and signaling components that contribute to salinity tolerance in B. juncea var. CS52.