Rice is the staple food for more than fifty percent of the world's population, and is therefore an important crop. However, its production is hindered by several biotic and abiotic stresses. Although rice is the only crop that can germinate even in the complete absence of oxygen (i.e. anoxia), flooding (low oxygen) is one of the major causes of reduced rice production. Rice germination under anoxia is characterized by the elongation of the coleoptile, but leaf growth is hampered. In this work, a comparative proteomic approach was used to detect and identify differentially expressed proteins in the anoxic rice coleoptile compared to the aerobic coleoptile. Thirty-one spots were successfully identified by MALDI-TOF MS analysis. The majority of the identified proteins were related to stress responses and redox metabolism. The expression levels of twenty-three proteins and their respective mRNAs were analyzed in a time course experiment.

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Drought stress causes lower crop production globally. Plants have acquired many adaptations to overcome drought stress. Mungbean (Vigna radiata (L.) R.Wilczek) is a legume crop widely cultivated in South, East and Southeast Asia. It is grown in high-temperature areas where drought is the main cause of reduced plant growth and productivity. Plants cope with drought stress by activating different signalling mechanisms. The sucrose non-fermenting-1-related protein kinase 2 family (SnRK2s) is known to play vital roles in osmotic stress and in abscisic acid (ABA) signalling pathways by phosphorylating downstream targets. The genes encoding SnRK2s in mungbean and their detailed characterisation remain unexplored. We have conducted extensive genome-wide analysis for gene prediction, in silico gene analysis, evolutionary analysis and gene-expression profiling under drought-stress conditions by quantitative real-time PCR. Through genome-wide analysis, eight SnRK2 genes were predicted in the mungbean genome and were assigned the names VrSnRK2.1–VrSnRK2.8, according to their order on the chromosomes. The VrSnRK2 genes identified were classified into three clusters based on their phylogenetic relationship with those of Arabidopsis thaliana. Drought stress was imposed on 11-day-old mungbean plants by completely withholding water for 3 days. According to real-time qPCR data, the expression of most of the VrSnRK2 genes was induced by drought stress, indicating their role in the drought-stress response. One of the genes, namely SnRK2.6c, showed highest expression level (12-fold) under drought stress, possibly indicating a critical role under water-deficit conditions. These data provide important information about the VrSnRK2 gene family in mungbean. The results will help in future functional characterisation of VrSnRK2 genes.

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Mungbean (Vigna radiata L.) is a valuable legume crop grown in tropical and subtropical areas of Asia. Drought is one of the major factors hindering its growth globally. APETALA2/ethylene-responsive element factor binding proteins (AP2/ERF) are an important family of plant-specific transcription factors (TFs) involved in drought-stress tolerance. We identified 71 AP2/ERF TFs in the mungbean genome by using bioinformatics tools and classified them into subfamilies: AP2 (16 members), ERF (22), RAV (2), DREB (30) and soloist (other proteins with no domain, 1). Members of DREB play a critical role in drought-stress tolerance. Ten-day-old mungbean plants cv. AZRI-06 were exposed to drought stress by complete withholding of water for 7 days. Root samples were collected from control and drought-stressed plants, and the expression pattern of 30 identified VrDREB genes was determined by qPCR. Most VrDREB genes exhibited differential expression in response to drought. Five genes (VrDREB5, VrDREB12, VrDREB13, VrDREB22, VrDREB30) were highly expressed under drought stress and might be considered excellent candidates for further functional analysis and for improvement of mungbean drought tolerance.