Proteomic analysis of preharvest sprouting in rye using two-dimensional electrophoresis and mass spectrometry

Qualitative and quantitative differences were found between two-dimensional electrophoretic spectra of 546 proteins from two bulked samples of mature rye grain representing: (1) 20 recombinant inbred lines extremely resistant to preharvest sprouting and (2) 20 recombinant inbred lines extremely susceptible to preharvest sprouting. Mass spectrometry of resolved proteins showed that four spots specific for PHS susceptibility represented high molecular weight glutenin subunit, glutathione transferase, 16.9 kDa heat-shock protein, and monomeric alpha-amylase inhibitor. Two spots specific for PHS resistance contained cytosolic malate dehydrogenase and functionally unrecognized protein with sequence homology to rubber elongation factor protein. Majority of 14 proteins with at least two-fold higher accumulation level in preharvest sprouting susceptible lines relative to that found in sprouting resistant lines, showed sequence homology to proteins involved in defense mechanisms against biotic and abiotic stresses including oxidative stress, and those taking part in energy supply. Two spots were identified as regulatory proteins from the 14-3-3 family with one molecular form prevailing in sprouting susceptible and another form highly accumulated in sprouting resistant lines. Further study establishing map positions of the revealed structural genes in respect to quantitative trait loci for preharvest sprouting in rye should answer the question on their possible status as candidate genes.