Biology

Professor David J. Hannapel
Iowa State University Ames, USA

Potato is the third most important subsistence crop grown worldwide. Identifying signals that control tuberization can readily lead to molecular strategies to yield enhancement. Tuberization in potato is activated by signals that arise in leaves moving down into stolon tips, inducing tuber formation. Three critical signals have recently been identified: StCDF1 for earliness and StBEL5 and StSP6A protein as mobile signals arising from the leaf. StCDF1 is a transcriptional regulator that controls maturity and onset of tuberization by downregulating the repressive activity of StCONSTANS. StSP6A is a co-regulator, a potato FT ortholog, whereas StBEL5 is a transcription factor that is transported as a full-length mRNA escorted by its protein chaperones to stolons where it is translated. StBEL5 front-loads activity in the leaf through the transcriptional induction of both StCDF1 and StSP6A. Localization of the signal into stolons is regulated by transport of StSP6A and StBEL5 mRNA. Amplification of the signals occurs in stolons, where StBEL5 plus its KNOX partner induces transcription of both StSP6A and StBEL5. In this evolving model, StBEL5 functions to activate tuberization, and at the same time, to amplify other pivotal signals in the pathway. This presentation will illuminate our current understanding of tuberization by focusing on the dynamic interactions of its three most important signals and comparing these to components in the floral signaling pathway.