Date: Saturday, January 14, 2012
Time: 12:00 PM
Time: 12:00 PM
Room: Pacific Salon 2
Seasonal fluctuations in day length regulate important aspects of plant development such as flowering transition or, in potato, storage organ formation. Short days (SD) were reported to induce the synthesis of a mobile tuberization-inducing signal or tuberigen in the leaves, that is transported to the underground stems or stolons to initiate tuber formation. A daylength-dependent pathway involving function of the potato CONSTANS homologue appears to mediate synthesis of this leaf-derived signal, but remained to be established whether the FT florigen or a different sort of mobile signal plays in tuberization control. Here we show that ectopic expression of the rice FT Hd3a gene in andigena potatoes induces tuberization under non-inductive long days (LD), FT therefore acting as a strong tuberization inducer. Tuberization promotion is transmitted to wild-type stocks across the graft junction and the transported Hd3a protein is detected in the stolon tips of the recipient plants. Analysis of the potato FT gene family identified two different FT paralogs, i.e. the potato StSP6A and StSP3D genes, that are up-regulated in response to short day conditions or high light irradiance and that play major roles in SD tuberization or day neutral floral transition. While StSP3D lost photoperiodic control, StSP6A is regulated in a day length-dependent manner by CO. We show that activation of this gene mediates strict short-day tuberization control of andigena species and its up-regulation correlates with early/late tuberization transition of commercial varieties. Hence, potato FT-like genes acquired major roles in flowering and tuberization control through changes in their expression profiles, although they encode for functionally similar proteins. Data will also be presented for different light dependent regulation of the potato and Arabidopsis CONSTANS proteins, different light-stability of these proteins likely accounting for LD/SD-dependent FT-activation in these species.