Changes in tomato ovary transcriptome demonstrate complex hormonal regulation of fruit set

Abstract

Summary• Plant hormones are considered to be important mediators of the fruit developmental signal after pollination. The role of phytohormones in tomato ( Solanum lycopersicum ) fruit set was investigated here.• Transcriptome analysis of ovaries was performed using two complementary approaches: cDNA-amplified fragment length polymorphism (AFLP) and microarray analysis.• The gene expression profiles obtained suggest that, in addition to auxin and gibberellin, ethylene and abscisic acid (ABA) are involved in regulating fruit set. Before fruit development, many genes involved in biotic and abiotic responses are active in the ovary. In addition, genes involved in ethylene and ABA biosynthesis were strongly expressed, suggesting relatively high ethylene and ABA concentrations before fruit set. Induction of fruit development, either by pollination or by gibberellin application, attenuated expression of all ethylene and ABA biosynthesis and response genes within 24 h.• It is proposed that the function of ABA and ethylene in fruit set might be antagonistic to that of auxin and gibberellin in order to keep the ovary in a temporally protected and dormant state; either to protect the ovary tissue or to prevent fruit development before pollination and fertilization occur.

Abscisic acid levels in tomato ovaries are regulated by LeNCED1 and SlCYP707A1

“…Gibberellins and auxins were known previously to induce fruit growth and, by demonstrating that ABA signaling is high in mature ovaries and decreases after pollination, we have recently suggested a role for ABA in fruit set (Vriezen et al 2008). In additional, ABA has been immuno-localized in the ovary of Arabidopsis and cucumber, indicating a function for ABA in these tissues (Peng et al 2006).…”

“…Abscisic acid signaling and ABA response genes are highly expressed in unpollinated ovaries and their expression decreases upon pollination (Vriezen et al 2008), suggesting a concomitant decrease in ABA concentration. To conWrm this assumption, ABA concentration was determined in ovaries at several time points before and after pollination.…”

“…In plant cells, ABA is mainly inactivated by 8Ј-hydroxylation (Nambara and Marion-Poll 2005), which is in Arabidopsis catalyzed by four cytochrome P450 mono-oxygenases, AtCYP707A1 to AtCYP707A4 (Kushiro et al 2004). We previously identiWed a tomato homolog of AtCYP707A4, which was strongly induced in the ovary after pollination (Vriezen et al 2008). We have now isolated and characterized the corresponding full-length (1,742 bp) cDNA clone from a tomato ovary cDNA library.…”

“…We have used transcript proWling to gain a better insight into the genes involved in fruit initiation, focusing on genes involved in hormonal signaling. Several groups of genes were found to have altered mRNA levels after pollination including genes involved in the cell cycle, posttranscriptional gene regulation, GA biosynthesis and auxin signaling (Vriezen et al 2008). Notably, several genes related to abscisic acid (ABA), such as ABA RESPONSE ELEMENT BINDING PROTEIN 1, ABA INSENSITIVE1-like genes, and dehydrin genes, were found to be highly expressed in mature ovaries while their expression decreased after pollination (Vriezen et al 2008).…”

“…Several groups of genes were found to have altered mRNA levels after pollination including genes involved in the cell cycle, posttranscriptional gene regulation, GA biosynthesis and auxin signaling (Vriezen et al 2008). Notably, several genes related to abscisic acid (ABA), such as ABA RESPONSE ELEMENT BINDING PROTEIN 1, ABA INSENSITIVE1-like genes, and dehydrin genes, were found to be highly expressed in mature ovaries while their expression decreased after pollination (Vriezen et al 2008). Many factors related to ABA signaling and ABA responses are thus higher in mature, unpollinated ovaries and are quickly reduced after pollination.…”