Figure 3.
crwn double mutants exhibit cell death and PR gene expression, which are exacerbated with aging. A, Trypan Blue staining showed that crwn1 crwn2 and crwn1 crwn4 mutants form spontaneous lesions. As plants matured, cell death was more apparent and more frequent. B, PR1 expression in leaves from crwn1 crwn2 mutants of different ages. Expression of PR1 is higher in chronologically older leaves of crwn1 crwn2 mutants, consistent with our observation that older plants develop more lesions. PR1 expression at each stage was normalized to transcript levels in wild-type samples for the housekeeping gene ROC1. Error bars indicate se (n = 3). Student’s t tests were performed based on delta-Ct values (*, P < 0.05 and ***, P < 0.001). C, The sid2-1 mutation suppressed cell death in 22-d-old crwn1 crwn2 mutants; however, 30-d-old plants still exhibited some lesion formation. Bars = 100 mm.