Chlorophyll catabolism pathway in fruits of Capsicum annuum (L.): stay-green versus red fruits

The aim of the present study is to investigate the chlorophyll catabolism pathway of wild-type red and stay-green mutants of Capiscum annuum (L.) fruits. In the wild-type red lines chlorophyll catabolism is concomitant with the start of carotenogenesis, whereas in the stay-green mutant lines the chlorophylls coexist with that process, even in over-ripe fruit. During the first stages of ripening, the chlorophyll a/chlorophyll b ratio is similar for both genotypes, but as ripening proceeds, the ratio in the stay-green lines becomes very high as a result of a blocked degradation of chlorophyll a while chlorophyll b is degraded at a normal rate. The absence of dephytylated chlorophylls in the wild-type lines distinguishes these from the mutant lines, in which there is a sequential accumulation of chlorophyllide a and pheophorbide a. Allomerized chlorophylls (13(2)-OH-chlorophyll a and b) have also been identified in the catabolic process of the mutant lines, but are absent from the wild type. Consequently, an alteration in pheophorbide a oxygenase (PaO) activity seems to be responsible for the stay-green genotype in the lines of pepper analyzed in this study.