Investigating a potential role for SQUAMOSA promoter-binding protein (SBP) transcription factors as positive regulators of programmed cell death in tomato
R. KESSENS (1) (1) University of Wisconsin - Madison, U.S.A.

Treatments for many human diseases have greatly advanced due in part to extensive research on programmed cell death (PCD) in animals. The misregulation of PCD has also been implicated in many plant diseases but our understanding of this process in plants is severely lacking. This is largely due to the absence of conserved animal PCD regulators in plant genomes. This includes caspases, which are cysteine proteases responsible for executing the death signal, and the Inhibitor of Apoptosis (IAP) proteins, which negatively regulate caspase activity. While plants lack homologues of caspases and IAPs, heterologous expression of an insect IAP from Spodoptera frugiperda (SfIAP) can inhibit PCD caused by the mycotoxin fumonisin B1 (FB1) and the necrotrophic fungus Alternaria alternata in tomato. To determine the biochemical context of SfIAP in tomato, we conducted a yeast two-hybrid assay using SfIAP as bait to screen a tomato cDNA library. Putative interactors of SfIAP were enriched with members of the SQUAMOSA promoter binding protein (SBP) family of plant-specific transcription factors. Overexpression of our top SfIAP-interactor, SlySBP12a, induces lesion mimics in N. benthamiana leaves in a manner dependent on its nuclear localization. Additionally, we have evidence that SlySBP12a activity requires cleavage from an intracellular membrane as overexpression of SlySBP12a lacking a putative transmembrane domain causes enhanced cell death as determined by electrolyte leakage. These results suggest that SlySBP12a is a positive regulator of PCD that controls the expression of PCD-associated genes.

Abstract Number: P9-267
Session Type: Poster