Transcriptional Analysis of Polygalacturonase and Other Ripening Associated Genes in Rutgers, rin, nor, and Nr Tomato Fruit

We have studied the transcription of polygalacturonase (PG) and several other riponing-associated genes in wild-type tomato (Lycopersicon esculentum) fruit and three ripening-impaired mutants, rin, nor, and Nr. In wild-type fruit, the PG gene becomes transcriptionally active early in ripening and remains transcriptionally active during the ripening process. Fruit of the three ripening-impaired mutants, which have reduced levels of PG mRNA, have correspondingly reduced PG transcription rates. Other ripening-associated genes showed diverse patterns of expression in the ripening-impaired mutant backgrounds. These results indicate that transcriptional activation of the PG gene is an important control point regulating the expression of PG during ripening in wild-type fruit and that PG expression in rin, nor, and Nr fruit is blocked at the level of transcription. A comparison of PG transcription rates and mRNA levels with those of other ripening-associated genes suggests that posttranscriptional processes may also contribute to the large accumulation of PG mRNA during ripening.