Drought stress adaptation: metabolic adjustment and regulation of gene expression

Plants cope with drought stress by manipulating key physiological processes like photosynthesis, respiration, water relations, antioxidant and hormonal metabolism. There exist multiple and often redundant stress sensors, which transduce the stress signal through secondary signalling molecules to the nucleus, where the expression of stress-response genes is regulated. Transcription factors play an important role in regulating the expression of the stress-response genes. Another level of regulation of gene expression is at the epigenetic level and involves modifications either at the chromatin level or at the mRNA level. Crop plants show various adaptive and acclimatization strategies to drought stress, which range from seemingly simple morphological or physiological traits that serve as important stress tolerance markers to major upheavals in gene expression in which a large number of transcription factors are induced. Studies on contrasting crop genotypes or genetic engineering of crops help in differentiating responses to drought from those leading to drought tolerance. Of specific importance to crop plants is not whether they survive stress, but whether they show good yields under stress conditions.