Chlorophyll catabolism and gene expression in the peel of ripening banana fruits

The biochemical and molecular basis of chlorophyll (Chl) catabolism in bana nas was investigated during ripening at 20 degrees C and at an elevated tem perature (35 degrees C) where degreening is inhibited. Biochemical analysis showed that Chl breakdown products could be isolated from fruit ripened at both temperatures. The coloured breakdown products, chlorophyllide and phe ophorbide, were not detected at any stage of ripening in the two treatments ; however, a non-fluorescent Chi catabolite accumulated to a higher concent ration at 20 than at 35 degrees C. To investigate the ripening-related gene expression associated with these changes, a cDNA library was generated fro m the peel of fruit ripened at 20 degrees C, Differential screening of this library produced 20 non-redundant families of clones including those encod ing enzymes involved in ethylene biosynthesis, respiration, starch metaboli sm, cell wall degradation and other metabolic events. The expression of the se genes was followed by northern analysis in fruit ripened at 20 and 35 de grees C.