关键词: 番茄, 番茄生长素响应因子12, RNA干扰, 果实形态, 细胞膨大, 基因表达

Abstract:

In order to explore the molecular mechanism by which auxin signal transduction mediates fruit set and development，we used tomato variety‘Micro-Tom’to evaluate the biological function of an auxin responsive factor，SlARF12（HM565127.1），in fruit development. Real-time PCR analysis showed that the SlARF12 mRNA levels gradually decreased before the flower was fully open，however，it became significantly higher in self-pollinated ovaries than that in emasculated and unpollinated ones. Inhibition of SlARF12 by RNA interference（RNAi）method had no significant influence on tomato vegetative growth and flower development，but the RNAi fruits in transgenic plants were significantly larger and heavier than those in wild-type plants and empty vector transgenic lines. In addition，no parthenocarpic fruit was developed after artificial emasculation before anthesis. The semi-thin section was performed to compare cytological characteristics in early fruits between RNAi and wild-type plants. The fruit pericap cells of transgenic lines were significantly larger than those of wild-type fruits，but the number of pericap cell layers of transgenic fruit was similar to that of the control fruit. Gene expression analysis showed that the mRNA levels of cell differentiation genes including CycB1.1 and CDKB2.1 in the ovary and young fruit of SlARF12 RNAi transgenic plants decreased when compared with the wild-type fruits，but the expression level of cell expansion gene such as SlPEC was significantly higher than that of the control fruit. Therefore，the inhibition of the SlARF12 expression level would up-regulate the expression levels of cell expansion genes，which might enhance the ability of fruit expansion and result in larger fruits of transgenic plants. The data suggest that SlARF12 can negatively regulate the fruit expansion process in tomato but is not required for fruit initiation，revealing the auxin can finely regulate fruit development at various stages through ARF signal conduction pathway.

Key words: tomato, SlARF12, RNA interference, fruit morphology, cell expansion, gene expression