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We have analyzed macromolecular changes that are associated with natural leaf senescence in Arabidopsis thaliana . The loss of chlorophyll that is characteristic of leaf senescence is accompanied by a specific pattern of decline of total RNA and protein levels. We have constructed two cDNA libraries representing mRNAs from Arabidopsis leaves at different senescence stages. Six cDNA clones corresponding to mRNAs that substantially increase in abundance during senescence were isolated. The levels of these mRNAs remain elevated into the late stages of senescence when most of the chlorophyll and protein of the leaf has been degraded. Sis cDNA clones that correspond to mRNAs that exhibit contrasting behavior were also identified: the levels of these mRNAs decrease to undetectable levels during senescence. The changes in the levels of these specific mRNAs during the course of senescence are presented. The results indicate that major changes in gene expression occur in Arabidopsis leaves during the process of senescence.
Lohman et al. (Sat,) studied this question.