Stress Related Genes

Genes involved in stress responses may directly affect longevity and senescence through protection of cells and tissues from environmental stresses. Recently, expression profiles of 402 potential stress-related genes that encode known or putative transcription factors from Arabidopsis were monitored in various organs, at different developmental stages, and under various biotic and abiotic stresses (Chen et al., 2002). Among the 43 transcription factor genes that have been reported to be induced during senescence, 28 of them also are induced by stress treatment, suggesting extensive overlap responses to these stresses. There are several reports on increasing plant tolerance to various environmental stresses through genetic manipulation, for example, expression of DREB1A from the stress-inducible rd29A promoter gives rise to drought, salt, and freezing tolerance (Kasuga et al., 1999). There is no formal report on the role of stress response genes in plant senescence yet; however, it seems likely that enhanced stress resistance would also increase longevity. Preliminary evidence, albeit with oxidative stress, suggests that this is true (Kurepa et al., 1998).

It is also known that many stress-related genes are induced during senescence. These include metallothionein-like genes from rice and Arabidopsis (Hensel et al., 1993; Hsieh et al., 1995) and genes involved in the oxidative stress response such as ascorbate oxidase (Callard et al., 1996) and anionic peroxidase (Tournaire et al., 1996). These genes may play a role in protecting the cellular functions required for progression and completion of senescence. It is likely that they affect progression of senescence at least partially. Interestingly, the Arabidopsis thaliana protein CEF makes yeast more tolerant to hydroperoxides, affirming the genetic control of stress resistance (Belles-Boix et al., 2000).

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