New Evidence for the Role of Ethylene in Strawberry Fruit Ripening

It has been suggested that the phytohormone ethylene plays a role in strawberry fruit ripening, and new genetic evidence for the role of this hormone in strawberry ripening is provided in this study. The combined analysis of ethylene production and transcripts of the ethylene biosynthesis-related gene FaSAMS1 and the signaling gene FaCTR1 in 'Camarosa' strawberry (Fragaria ananassa) fruit showed that an increase in ethylene production was concomitant with a rise in transcripts of the two genes during fruit red-coloring, suggesting that FaSAMS1 and FaCTR1 might play a role in fruit ripening. Downregulation of the FaSAMS1 or FaCTR1 transcript via a recently reported tobacco rattle virus-induced gene-silencing technique not only inhibited fruit red-coloring and firmness, but it also promoted ethylene biosynthesis. Furthermore, the latter also affected a series of ethylene-signaling components. Importantly, applied ethephon could promote natural strawberry fruit red-coloring and softening and partially rescue anthocyanin biosynthesis in the two-type RNAi fruit, but could not markedly affect RNAi fruit firmness. These data provide new evidence that FaCTR1 positively regulates strawberry fruit ripening and that ethylene is required for strawberry fruit ripening.