Knowledge Bank

Senescence is a highly regulated process and the final stage of plant development, which ultimately results in the programmed death of cells, organs, tissues or whole plants. Caspases are key regulators of the cell death program in animals, but to date no homologs of caspases have been found in plant genome databases. While caspase-like activity has recently been demonstrated in various plant cell death models, the corresponding genes for these activities have never been identified. While a caspase related family of proteases (metacaspases) has been identified in plant and fungal genomes using iterative PSI-BLAST, the function of metacaspases in plants is still largely unknown. As a first step to understanding the role of metacaspases, a type I (PhMCA1) and a type II (PhMCA2) metacaspase have been cloned from Petunia x hybrida cv Mitchel Diploid. The expression of PhMCA1 and PhMCA2 has been investigated in various petunia tissues using real-time RT-PCR PhMCA1 transcript abundance increased during flower senescence, while abundance of PhMCA2 increased following Botrytis cinerea infection. PhMCA1 expression was not increased in ethylene insensitive petunias during flower senescence. In order to further investigate the functional role of PhMCA1, RNAi lines have been generated and phenotypic analyses of T1 plants is underway.