RNAi silencing of chalcone synthase , the first step in the flavonoid biosynthesis pathway , leads to parthenocarpic tomato fruits

Parthenocarpy, the formation of seedless fruits in the absence of functional fertilisation, is a desirable trait for several important crop plants including tomato (Solanum lycopesicum). Seedless fruits can be of great value for consumers, processing industry and breeding companies. In this paper we propose a novel strategy to obtain parthenocarpic tomatoes, by down-regulation of the flavonoid biosynthesis pathway using RNAi mediated suppression of chalcone synthase, the first gene in the flavonoid pathway. In CHS RNAi plants, total flavonoid levels, transcript levels of both Chs-1 and Chs-2, as well as CHS enzyme activity were reduced up to a few percent of the corresponding wild type values. Surprisingly, all strong Chs silenced tomato lines developed parthenocarpic fruits. Although a relation between flavonoids and parthenocarpic fruit development has never been described, it is well-known that flavonoids are essential for pollen development and pollen tube growth, and hence play an essential role in plant reproduction. The observed parthenocarpic fruit development appeared to be pollination-dependent and Chs RNAi fruits displayed impaired pollen tube growth. Our results lead to novel insight in the mechanisms underlying parthenocarpic fruit development. The potential of this technology for applications in plant breeding and biotechnology will be discussed.