Use of a tomato mutant constructed with reverse genetics to study fruit ripening, a complex developmental process

摘要

AbstractFruit ripening is one of the most dramatic developmental transitions associated with extensive alteration in gene expression. The plant hormone ethylene is considered to be the causative ripening agent. Transgenic tomato plants were constructed expressing antisense or sense RNA to the key enzyme in the ethylene (C2H4) biosynthetic pathway, 1 ‐aminocyclopropane‐1‐carboxylate (ACC) synthase using the constitutive CaMV 35S and fruit specific E8 promoters. Fruits expressing antisenseLE‐ACS2RNA produce less ethylene and fail to ripen only when ethylene production is suppressed by more than 99 (>0.1 nl/g fresh weight). Ethylene production is considerably inhibited (50) in fruits expressing senseLE‐ACS2RNA. Antisense fruits accumulate normal levels of polygalacturonase(PG), ACC oxidase(pTOM13),E8, E17, J49, and phytoene desaturase(D2)mRNAs which were previously thought to be ethylene‐inducible.E4gene expression is inhibited in antisense fruits and its expression is not restored by treatment with exogenous propylene (C3H6). Antisense fruits accumulate PG mRNA, but it is not translated. Immunoblotting experiments indicate that the PG protein is not expressed in antisense fruits but its accumulation is restored by propylene (C3H6) treatment. The results suggest that at least two signal‐transduction pathways are operating during tomato fruit ripening. The independent (developmental) pathway is responsible for the transcriptioncl activation of genes such asPG, ACC oxidase,E8, E17, D2, andJ49.The ethylene‐dependent pathway is responsible for the transcriptional and posttranscriptional regulation of genes involved in lycopene, aroma biosynthesis, and the translatability of developmentally regulated genes such asPG. © 1993Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.©