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Plants are subjected to several abiotic stresses that adversely affect growth, metabolism and yield. The dynamic research in plant genetics complemented by genome sequencing has opened up avenues to address multiple problems caused by abiotic stresses. Though many drought-induced genes have been phytoengineered in a wide range of plants, the drought signal transduction pathways, and the alteration of plant sensing and signaling systems to adverse environments still remain an intriguing subject for comprehensive investigation. To impart enhanced drought tolerance in plants, a thorough perception of physiological, biochemical and gene regulatory networks is essential. Recent functional genomics tools have facilitated the progress in our understanding of stress signaling and of the linked molecular regulatory networks. This has revealed several stress-inducible genes and various transcription and signaling factors that regulate the drought stress-inducible systems. Translational genomics of these drought specific genes using model plants have provided encouraging outcomes, but the in-depth knowledge of the specific roles of various metabolites in plant stress tolerance will lead to evolvement of strategies for the phytoengineering of drought tolerance in plants in future.

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Agrobacterium-mediated transformation of indica rice has been established in only a limited number of cultivars because the regeneration of plants from transformed embryogenic calli is highly cultivar-specific. Establishment of a highly efficient plant regeneration system from shoot apex explants applicable to many cultivars of indica rice will accelerate the application of transformation technology in breeding programs and functional genomics study. We established an efficient shoot multiplication and plant regeneration system from shoot apices of indica rice using thidiazuron (TDZ) as a plant growth regulator. Shoot apices cultured on MS basal medium devoid of plant growth regulators formed solitary shoots in 90% of cultures. Addition of TDZ or benzylaminopurine to regeneration medium significantly influenced formation of multiple shoots directly from shoot apex explants without an intervening callus stage. Best shoot proliferation response (10.3 shoots per explant) was recorded when shoot apices were cultured on media supplemented with 4 mg/l TDZ. No synergistic effect on shoot proliferation was observed when indole-3-acetic acid and indole-3-butyric acid were supplemented to media containing 4 mg/l TDZ. The regeneration system was efficient in evoking multiple shoot proliferation in eight different cultivars of indica rice. Shoots were rooted in MS basal medium and plantlets were acclimatized with 100% survival rate. The shoot apex explants of all the eight cultivars of indica rice were found competent to Agrobacterium-mediated transformation while explants from IR-64 showed highest transient GUS expression. This variety-independent transformation amenable regeneration system from shoot apices may widely be applicable for genetic transformation of indica varieties.