Gene expression in the pulp of ripening bananas. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of in vitro translation products and cDNA cloning of 25 different ripening-related mRNAs.

摘要

mRNA was extracted from the pulp and peel of preclimacteric (day 0) bananas (Musa AAA group, cv. Grand Nain) and those exposed to ethylene gas for 24 h and stored in air alone for a further 1 (day 2) and 4 days (day 5). Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of in vitro translation products from the pulp and peel of these fruits revealed significant up-regulation of numerous transcripts during ripening. The majority of the changes were initiated by day 2, with thelevel of these messages increasing during the remainder of the ripening period. Pulp tissue from day 2 was used for the construction of a cDNA library. This library was differentially screened for ripening-related clones using cDNA from day 0 and day 2pulp by a novel microtitre plate method. In the primary screen 250 up- and down-regulated clones were isolated. Of these, 59 differentially expressed clones were obtained from the secondary screen. All of these cDNAs were partially sequenced and groupedinto families after database searches. Twenty-five non-redundant groups of pulp clones were identified. These encoded enzymes were involved in ethylene biosynthesis, respiration, starch metabolism, cell wall degradation, and several other key metabolic events. The analysis of these clones and their possible involvement in ripening are described.