Microarray analysis of ripening tomato fruits with RNAi knockdown of a direct RIN-target GRAS family gene

The tomato (Solanum lycopersicum) MADS-box transcription factor RIPENING INHIBITOR (RIN) acts as a master regulator of tomato fruit ripening. We previously identified a direct RIN target gene Solyc07g052960, which encodes a putative GRAS family protein belonging to the SHORT-ROOT (SHR) branch, but its role was unknown. RNA interference (RNAi)-mediated gene silencing reduced Solyc07g052960 expression in transgenic fruits, but the fruits appeared to ripen normally. However, the transgenic fruits at the ripening stage showed a marked decrease of the expression levels of several ripening-induced genes, especially involved in cell wall modification and secondary metabolism. This suggests that Solyc07g052960 participates in the regulation of these processes as one component of the RIN-activated transcriptional cascade regulating fruit ripening in tomato. For a preliminary screening, we monitored global gene expression in tomato fruits from untransformed control (Ailsa Craig [AC] cultivar) and three transgenic lines with Solyc07g052960 knockdown by RNAi (lines T-7, T-22 and T-23) at the ripening (pink coloring) stage using microarray without biological replication.