UDP-Glucose Pyrophosphorylase Is a Novel Plant Cell Death Regulator

Programmed cell death (PCD) is an essential process that functions
in plant organ sculpture, tissue differentiation, nutrient recycling,
and defense against pathogen attack. A full understanding of the mechanism
of PCD in plants is hindered by the limited identification of protein
components of the complex signaling circuitry that underpins this
important physiological process. Here we have used Arabidopsis
thaliana and fumonisin B1 (FB1) to identify proteins that
constitute part of the PCD signaling network. We made an inadvertent,
but important observation that exogenous sucrose modulates FB1-induced
cell death and identified sucrose-induced genes from publicly available
transcriptomic data sets for reverse genetic analyses. Using transfer-DNA
gene knockout plants, UDP-glucose pyrophosphorylase 1 (UGP1), a sucrose-induced gene, was demonstrated to be a critical factor
that regulates FB1-induced PCD. We employed 2D-DiGE to identify proteomic
changes preceding PCD after exposure of Arabidopsis to FB1 and used UGP1 knockout plants to refine
the analysis and isolate downstream candidate proteins with a putative
PCD regulatory function. Our results reveal chloroplasts as the predominantly
essential organelles in FB1-induced PCD. Overall, this study reveals
a novel function of UGP1 as a cell death regulator and provides candidate
proteins likely recruited downstream in the activation of plant PCD.