PP 1530: An IDD Transcription Factor Involved in Sugar-Induced Flowering and Tuberization in Solanum Tuberosum

In potato plants (Solanum tuberosum) both flower and tuberization transitions employ similar inducing pathways. Since potato is cultivated for its underground storage organs, the time to tuberization and the tuber yield is of growing significance in terms of food security, which is why the identification of factors and tuber inducing mechanisms also affecting tuber quality traits is of broadest interest in plant research and agriculture. In this proposal we suggest the characterization of pathways affecting flowering and tuberization in potato within the framework of the priority program SPP1530 (Phase II). The POTATO COUCH POTATO1 (StPCP1) protein is a transcription factor of the IDD transcription factor family. StPCP1 RNAi plants show a flowering and tuberization phenotype. Preliminary quantitative real time PCR analyses suggest that StPCP1 is a general regulator of sugar transporters thereby influencing the carbohydrate status in potato plants. Several phloem mobile signals have been suggested to report of the sucrose status of source leaves to sink organs such as the shoot apical meristem or the stolon tips. We plan on investigating these putative phloem mobile factors in more detail, in particular trehalose-6 phosphate, miR156 and miR172 as well as their targets. We further propose characterizing the nature of StPCP1 as a transcription factor as well as its downstream targets. This specifically involves the direct regulation of sucrose transporters (e.g. StSUT4) and the regulation of further downstream targets via the binding of the known ID1 domain. At the same time we will address open questions regarding the interaction with known signaling pathways leading to flowering and tuberization in potato, i.e. the photoperiod, the T6P and the GA pathways, as they have been shown to be affected by StPCP1.