Proteomic analysis of the regulatory network involved in long-distance signaling in potato
Project leader: Shweta Shah, Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University (firstname.lastname@example.org)
The objective of this study is to uncover the network of signals that are responsible for the photoperiod-activated induction of tuber formation. In potato (Solanum tuberosum), BEL5 mRNA is a mobile RNA which is involved in the signaling system that activates tuber formation. Short day (SD) induces tuberization and long day (LD) inhibits the process. The mobility of StBEL5 RNA is induced by a SD photoperiod. It is likely that the movement of StBEL5 is facilitated by the formation of a RNA-protein complex. To verify this proposed mechanism of downstream signaling we have undertaken a detailed proteomic analysis and have successfully identified several RNA-binding proteins. Proteins from potato petioles (as the transcriptional source of StBEL5 RNA is leaf veins and petioles) grown under LD and SD photoperiod conditions were separated by 2-dimensional gel electrophoresis (2-DE). Proteins which were differentially expressed in response to changes in photoperiods were analyzed by Progenesis SameSpots software and identified by MALDI MS/MS. Because phosphorylation of proteins is central to signal transduction, phosphoproteins from LD and SD potato petioles were also enriched, separated on 2-DE and similarly analyzed by MALDI MS/MS. RNA-binding proteins were also specifically enriched from LD and SD potato petioles by using a poly(U) sepharose column followed by 2-DE and mass spectrometric identification of proteins. We have so far identified nearly fifty proteins that are differentially expressed in response to LD or SD photoperiods and that exhibit differences greater than 1.5-fold. A comprehensive profile of the phosphoproteomes of LD and SD potato petioles has been established. Significantly, the presence of the RNA-binding protein, elF-5A, has been detected in multiple phosphorylation states specifically under LD conditions. Numerous poly(U)-binding proteins which contain RNA recognition motifs have also been isolated and identified.