ISOLATION AND CHARACTERIZATION OF A GENE ENCODING ENDO-BETA-1,4-GLUCANASE FROM PEPPER (CAPSICUM-ANNUUM-L)

The endo-beta-1,4-glucanases, or cellulases, of higher plants are cell wall-associated enzymes believed to function in cell wall changes ass ociated with the diverse processes of fruit ripening, organ abscission and cell elongation. We have isolated and characterized cDNA and geno mic clones encoding a cellulase, PCEL1, which is abundant in ripening pepper fruit. Genomic analysis indicates that PCEL1 is encoded by a si ngle gene, PCEL1, which belongs to a small, structurally divergent gen e family. In ripening fruit, PCEL1 transcription is initiated at two d istinct sites which yields overlapping mRNA species of 1.7 and 2.1 kb. High-level accumulation of both transcripts occurs in red fruit, whil e the 1.7 kb transcript is detected at a much lower level in stem and petiolar tissue. The increase in cellulase activity which is measured during fruit ripening is the product of PCEL1 expression and is tightl y coupled to fruit reddening. High-level applications of ethylene serv e to enhance the rate of ripening and the accumulation of PCEL1 mRNA. A direct role for ethylene in regulating PCEL1 expression is shown by the exclusive induction, in immature green fruit, of the 1.7 kb transc ript in response to prolonged high-level exposure to ethylene - a patt ern of expression not observed in fruit development on the vine.