Patterns of protein synthesis and tolerance of anoxia in root tips of maize seedlings acclimated to a low-oxygen environment, and identification of proteins by mass spectrometry

Tolerance of anoxia in maize root tips is greatly improved when seedlings a re pretreated with 2 to 4 h of hypoxia. We describe the patterns of protein synthesis during hypoxic acclimation and anoxia. We quantified the incorpo ration of [S-35]methionine into total protein and 262 individual proteins u nder different oxygen tensions. Proteins synthesized most rapidly under nor moxic conditions continued to account for most of the proteins synthesized during hypoxic acclimation, while the production of a very few proteins was selectively enhanced. When acclimated root tips were placed under anoxia, protein synthesis was depressed and no "new" proteins were detected. We pre sent evidence that protein synthesis during acclimation, but not during sub sequent anoxia, is crucial for acclimation. The complex and quantitative ch anges in protein synthesis during acclimation necessitate identification of large numbers of individual proteins. We show that mass spectrometry can b e effectively used to identify plant proteins arrayed by two-dimensional ge l electrophoresis. Of the 48 protein spots analyzed, 46 were identified by matching to the protein database. We describe the expression of proteins in volved in a wide range of cellular functions, including previously reported anaerobic proteins, acid discuss their possible roles in adaptation of pla nts to low-oxygen stress.