GENE-EXPRESSION IN THE PULP OF RIPENING BANANAS - 2-DIMENSIONAL SODIUM DODECYL SULFATE-POLYACRYLAMIDE GEL-ELECTROPHORESIS OF IN-VITRO TRANSLATION PRODUCTS AND CDNA CLONING OF 25 DIFFERENT RIPENING-RELATED MESSENGER-RNAS

mRNA was extracted from the pulp and peel of preclimacteric (d 0) bana nas (Mesa AAA group, cv Grand Nain) and those exposed to ethylene gas for 24 h and stored in air alone for a further 1 (d 2) and 4 d (d 5). Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophore sis of in vitro translation products from the pulp and peel of these f ruits revealed significant up-regulation of numerous transcripts durin g ripening. The majority of the changes were initiated by d 2, with th e level of these messages increasing during the remainder of the ripen ing period. Pulp tissue from d 2 was used for the construction of a cD NA library. This library was differentially screened for ripening-rela ted clones using cDNA from d-0 and d-2 pulp by a novel microtiter plat e method. In the primary screen 250 up-and down-regulated clones were isolated. Of these, 59 differentially expressed clones were obtained f rom the secondary screen. All of these cDNAs were partially sequenced and grouped into families after database searches. Twenty-five nonredu ndant groups of pulp clones were identified. These encoded enzymes wer e involved in ethylene biosynthesis, respiration, starch metabolism, c ell wall degradation, and several other key metabolic events. We descr ibe the analysis of these clones and their possible involvement in rip ening.