Methyl viologen induced changes in the Arabidopsis proteome implicate PATELLIN 4 in oxidative stress responses.

The photosynthesis-induced accumulation of reactive oxygen species in chloroplasts can lead to oxidative stress, triggering changes in protein synthesis, degradation, and the assembly/disassembly of protein complexes. We identified methyl viologen (MV)-induced changes in protein abundance in wild type (WT) Arabidopsis and in the oxidative stress-hypersensitive fsd1-1 and fsd1-2 knockout mutants that are deficient in the chloroplast IRON SUPEROXIDE DISMUTASE, FSD1, using shot-gun proteomics. The levels of proteins that are localized in chloroplasts and the cytoplasm were modified in all lines treated with MV. The fsd1 mutants showed significant remodelling of metabolic protein and chloroplast chaperone levels, together with increases in cytoplasmic, peroxisomal and mitochondrial proteins compared to the WT. Different responses in proteins involved in the disassembly of photosystem II/light harvesting chlorophyll a/b binding proteins were observed. Moreover, the abundance of PATELLIN 4, a phospholipid-binding protein highly expressed in stomata precursors, was decreased in response to MV. Reverse genetic studies using patl4 knockout mutants and a PATL4 complemented line indicate that PATELLIN 4 affects plants responses to oxidative stress by effects on stomatal closure.