Drought- and desiccation-induced modulation of gene expression in plants.

Desiccation is the extreme form of dehydration. Tolerance of desiccation is acquired by seeds and in resurrection plants, a small group of angiosperms. Desiccation tolerance is the result of a complex cascade of molecular events, which can be divided into signal perception, signal transduction, gene activation and biochemical alterations leading to acquisition of tolerance. Many of these molecular processes are also observed during the dehydration of non-tolerant plants. Here we try to give an overview of the gene expression programmes that are triggered by dehydration, with particular reference to protective molecules and the regulation of their expression. Potential transgenic approaches to manipulating stress tolerance are discussed.

Response of some Calvin cycle enzymes subjected to salinity shock in vitro.

Leaf enzyme extracts of 10 day old seedlings of horsegram were subjected to NaCl or Na2SO4 treatment in vitro. Salinity shock caused decline in the activities of RuBP carboxylase, R-5-P kinase, R-5-P isomerase and NADP-Gly-3-P dehydrogenase. At low concentrations, Na2SO4 did not alter the activities of R-5-P kinase, R-5-P isomerase and NADP-Gly-3-P dehydrogenase. RuBP carboxylase was found to be more sensitive to salt shock than the other enzymes studied. Further, NaCl was more toxic to the enzyme activities as compared to Na2SO4.