Proteomic Analyses of Thioredoxins and Mutants Indicate Specific Functions for These Proteins in Plants.

A large number of plastidial thioredoxins (TRX) are present in chloroplast and the specificity versus the redundancy of their functions is currently under discussion. Several results have highlighted the fact that each TRX has a specific target protein and thus a specific function. In this study we have found that in vitro activation of the fructose-1,6-bisphosphatase (FBPase) enzyme is more efficient when and type thioredoxins (TRXs) are used, whilst the type TRX did not have any effect. In addition, we have carried out a two-dimensional electrophoresis-gel to obtain the protein profiling analyses of the , , , , and Arabidopsis mutants. The results revealed quantitative alteration of 86 proteins and demonstrated that the lack of both the and type thioredoxins have diverse effects on the proteome. Interestingly, 68% of the differentially expressed proteins in and mutants were downregulated, whilst 75% were upregulated in , , and lines. The lack of TRX provoked a higher number of down regulated proteins. The contrary occurred when TRX was absent. Most of the differentially expressed proteins fell into the categories of metabolic processes, the Calvin⁻Benson cycle, photosynthesis, response to stress, hormone signalling and protein turnover. Photosynthesis, the Calvin⁻Benson cycle and carbon metabolism are the most affected processes. Notably, a significant set of proteins related to the answer to stress situations and hormone signalling were affected. Despite some studies being necessary to find specific target proteins, these results show signs that are suggest that the and type plastidial TRXs most likely have some additional specific functions.