Phosphate deficiency-dependent upregulation of UDP-glucose pyrophosphorylase genes is insensitive to ABA and ethylene status in Arabidopsis leaves

Abstract

The effects of inorganic phosphate (Pi) deficiency and ABA/ethylene status on expression of UDP-glucose pyrophosphorylase (UGPase) genes (Ugp), involved in sucrose/polysaccharide metabolism, were investigated. Both wild-type (wt), aba and abi mutants (ABA-deficient and -in-sensitive), etr, ein and eto (ethylene resistant and overproducing) grown on Pi-deficient and complete nutrient solution, as well as phol (Pi-deficient) mutants of Arabidopsis thaliana were used for experiments. Generally, Pi-deficiency conditions (including mannose feeding to decrease cytosolic Pi pool) resulted in an increase of Ugp expression in the leaves, under all experimental conditions. Mutant backgrounds reflecting differences in ABA or ethylene status/ sensitivity had no effect on the level of Ugp up-regulation by Pi-stress. Furthermore, feeding ABA to the leaves of wt and pho1 plants had no effect on Ugp expression, regardless of the sucrose status in the leaves. The data suggest that Pi deficiency leading to up-regulation of Ugp acts independently of ABA and ethylene status.