Chloroplast nitrite uptake is enhanced in Arabidopsis PII mutants

Abstract 

In higher plants, the PII protein is a nuclear-encoded plastid protein that regulates the activity of a key enzyme of arginine biosynthesis. We have previously observed that Arabidopsis PII mutants are more sensitive to nitrite toxicity. Using intact chloroplasts isolated from Arabidopsis leaves and ¹⁵N-labelled nitrite we show that a light-dependent nitrite uptake into chloroplasts is increased in PII knock-out mutants when compared to the wild-type. This leads to a higher incorporation of ¹⁵N into ammonium and amino acids in the mutant chloroplasts. However, the uptake differences do not depend on GS/GOGAT activities. Our observations suggest that PII is involved in the regulation of nitrite uptake into higher plant chloroplasts.

Abbreviations: Col, Colombia ecotype, Chl, Chlorophyll, DCMU, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, MSO, methionine sulfoximine, WS, Wassilewskija ecotype

Keywords: Arabidopsis, AtGLB1 gene, Chloroplasts, uptake, PII protein, T-DNA insertion mutant