Arabidopsis CPR5 is a senescence-regulatory gene with pleiotropic functions as predicted by the evolutionary theory of senescence.

Evolutionary theories of senescence predict that genes with pleiotropic functions are important for senescence regulation. In plants there is no direct molecular genetic test for the existence of such senescence-regulatory genes. Arabidopsis cpr5 mutants exhibit multiple phenotypes including hypersensitivity to various signalling molecules, constitutive expression of pathogen-related genes, abnormal trichome development, spontaneous lesion formation, and accelerated leaf senescence. These indicate that CPR5 is a beneficial gene which controls multiple facets of the Arabidopsis life cycle. Ectopic expression of CPR5 restored all the mutant phenotypes. However, in transgenic plants with increased CPR5 transcripts, accelerated leaf senescence was observed in detached leaves and at late development around 50 d after germination, as illustrated by the earlier onset of senescence-associated physiological and molecular markers. Thus, CPR5 has early-life beneficial effects by repressing cell death and insuring normal plant development, but late-life deleterious effects by promoting developmental senescence. As such, CPR5 appears to function as a typical senescence-regulatory gene as predicted by the evolutionary theories of senescence.

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