Genetic improvement of rice crop under high temperature stress: bridging plant physiology with molecular biology

Rice crop meets the calorific needs of the masses. High temperature stress has negative effects on the physiology and biochemistry of this crop. This is amply reflected from studies showing that heat stress has strong detrimental effects on photosynthetic efficiency, electrolyte leakage, lipid peroxidation, enzyme (superoxide dismutase, peroxidase, catalase, etc.) activities and transpiration rate at varied growth stages, ultimately affecting the total harvest of this crop. The macro cellular- and plant-level changes as of aboveare rooted inalterations at the molecular level, affecting the gene expression profiles, protein abundance and their interaction at the genomic level. With global warming at its pace, the cultivation of rice under field conditions is greatly threatened. Molecular analyses show that the response of rice to heat stress involves a host of genes including transcription factors, genes involved in calcium and hormonal signalling, reactive oxygen species metabolism genes and chaperones. Heat shock proteins (Hsps) are considered the key players with role in maintaining proteostasis under heat and related stresses. The expression of Hsps is centrally governed by heat shock factors (Hsfs). Hsps and Hsfs have emerged as the potential candidates for engineering stress tolerance in crop plants. Several attempts have been made in which rice genes have been incorporated in varied hosts and concurrently rice has been used as trans-host with various genes cloned from rice and other plant species. In this review, we provide an account of physiological, biochemical, transcriptomic and proteomic responses of rice crop to heat stress. The importance of ClpB-C/Hsp100 gene in heat stress tolerance and the potential heat shock factor(s) governing regulation of ClpB-C/Hsp100 for engineering heat stress tolerance in rice has been discussed.