DIFFERENTIAL EXPRESSION OF 2 ENDO-1,4-BETA-GLUCANASE GENES IN PERICARP AND LOCULES OF WILD-TYPE AND MUTANT TOMATO FRUIT

The mRNA accumulation of two endo-1,4-beta-D-glucanase genes, Cell and CeI2, was examined in the pericarp and locules throughout the develop ment of normal tomato (Lycopersicon esculentum) fruit and the ripening -impaired mutants rin and Nr. Both Cell and CeI2 were expressed transi ently at the earliest stages of fruit development during a period corr esponding to cell division and early cell expansion. In the pericarp, the mRNA abundance of both genes increased markedly at the breaker sta ge; the level of Cell mRNA decreased later in ripening, and that of Ce I2 increased progressively. CeI2 mRNA levels also increased at the bre aker stage in locules but after initial locule liquefaction was alread y complete. In rin fruit mRNA abundance of Cell was reduced and CeI2 w as virtually absent, whereas in Nr Cell was expressed at wild-type lev els and CeI2 was reduced. In wild-type fruit ethylene treatment slight ly promoted the mRNA accumulation of both genes. In rin fruit ethylene treatment strongly increased the mRNA abundance of Cell to an extent greater than in wild-type fruit, but CeI2 mRNA was absent even after e thylene treatment. These two endo-1,4-beta-D-glucanase genes, therefor e, do not show coordinated expression during fruit development and are subject to distinct regulatory control. These results suggest that th e product of the CeI2 gene contributes to ripening-associated cell-wal l changes.