Figure 7.

Senescence-Related Gene Expression and Chlorophyll Degradation Are Not Detected in mex1.

(A) Changes in expression in mex1 relative to the wild-type of 105 genes previously identified as senescence-induced (Gepstein et al., 2003). Expression levels obtained from the ATH1 GeneChip analyses of mature leaves are given on a log₂ scale. Note that most expression levels differ less than two-fold from the wild-type (indicated by the gray area).

(B) HPLC analysis of extracts of mature leaves of the wild-type and mex1. Chlorophyll catabolites were not detectable in either line. After induction of senescence by incubating the leaves in the dark for 5 d, fluorescent chlorophyll catabolites (FCCs), non-fluorescent chlorophyll catabolites (NCCs), and pheophorbide-like catabolites (PLs), identified by their characteristic spectra, were readily detectable in both lines. The quantification of total NCCs from analyses of four replicate, dark-treated samples, each comprising eight 7-mm leaf discs, is inset.