Proteomics analysis of the regulatory network involved in long‐distance signaling in potato

Abstract

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 we have undertaken a proteomic analysis. 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. Phosphoproteins (phosphorylation of proteins is central to signal transduction) and RNA binding proteins were also enriched from LD and SD potato petioles, separated on 2‐DE and analyzed by MALDI MS/MS. We have identified many proteins that are differentially expressed in response to LD or SD photoperiods. 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 only under LD conditions. Numerous RNA‐binding proteins have also been isolated and identified.