Induction of a cysteine protease cDNA from Mesembryanthemum crystallinum leaves by environmental stress and plant growth regulators

A cDNA clone encoding a cysteine protease was isolated from salinity-stressed Mesembryanthemum crystallinum. The deduced sequence of this full-length clone of 1483 bp encodes a pre-proprotein of 367 amino acids with a predicted molecular mass of 41 kDa. Southern blot analysis of genomic DNA indicated that this cDNA is a member of a small multigenic family. Northern and western blot analysis showed that both mRNA and protein expression are strongly induced in leaves in response to salinity stress. mRNA abundance is also enhanced by drought stress and exogenous application of cytokinin and methyl jasmonate, but not ABA. Sequence comparisons showed the encoded gene product shows highest sequence homology (47.7-57.2% identity) to a group of cysteine proteases proposed to have diverse proteolytic functions in higher plants. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.