A vacuolar cysteine proteinase, SLCYSPRO, and programmed cell death in tomato following germination

Programmed cell death (PCD) is a fundamental process that is commonly utilized by plants to recover and re-use valuable nutrients from unwanted cells. Recently a novel cysteine proteinase, SLCYSPRO, was identified in tomato. SLCYSPRO protein was shown to accumulate in post-germinative endosperms after storage protein mobilization and when PCD was predominant. Localization experiments using GFP fusion constructs indicated that SLCYSPRO is vacuolar and that the SLCYSPRO prodomain is both sufficient and necessary for vacuolar targeting. This cysteine proteinase also appears to be regulated by various plant hormones; in particular that the addition of gibberellic acid and ethylene synergistically promote the accumulation of the enzyme in isolated tomato endosperms. An expression profile across the entire plant and immunohistochemistry suggest that SLCYSPRO is involved in vasculature development. Based on the localization, expression and accumulation patterns of SLCYSPRO it can be suggested that this proteinase plays a role in PCD.