XXXX metacaspase 2d is a positive mediator of cell death induced during biotic and abiotic stresses.

@entity462 @entity958 @entity18639 @entity3437 @entity204
@entity462 proteases such as caspases play important roles in @entity204 ( @entity204 ) of metazoans. Plant metacaspases (MCPs), a family of @entity462 proteases structurally related to caspases, have been hypothesized to be ancestors of metazoan caspases, despite their different substrate specificity. @entity958 contains six type II MCP genes (AtMCP2a-f). Whether and how these individual members are involved in controlling @entity204 in plants remains largely unknown. Here we investigated the function and regulation of AtMCP2d, the predominant and constitutively expressed member of type II MCPs, in stress-inducible @entity204 . Two AtMCP2d mutants (mcp2d-1 and mcp2d-3) exhibited reduced sensitivity to @entity204 -inducing mycotoxin @entity18639 as well as oxidative stress inducers, whereas AtMCP2d over-expressors were more sensitive to these agents, and exhibited accelerated cell-death progression. We found that AtMCP2d exclusively localizes to the cytosol, and its accumulation and self-processing patterns were age-dependent in leaves. Importantly, active proteolytic processing of AtMCP2d proteins dependent on its catalytic activity was observed in mature leaves during mycotoxin-induced cell death. We also found that mcp2d-1 leaves exhibited reduced cell death in response to @entity3437 carrying avirulent gene avrRpt2, and that self-processing of AtMCP2d was also detected in wild-type leaves in response to this pathogen. Furthermore, increases in processed AtMCP2d proteins were found to correlate with conditional cell-death induction in two lesion-mimic mutants (cpr22 and ssi4) that exhibit spontaneous cell-death phenotypes. Taken together, our data strongly suggest that AtMCP2d plays a positive regulatory role in biotic and abiotic stress-induced @entity204 .
