Identification of thioredoxin genes and analysis of their expression under abiotic stresses in Medicago truncatula

Thioredoxin (Trx) is a ubiquitous heat-stable protein that acts as an electron donor in many reduction reactions and is expressed in all organisms. In this study, the Trxs were searched from the whole genome of Medicago truncatula. As a result, 46 MtTrx genes were found and grouped into four groups by phylogenetic analysis. Chromosomal location and synteny analyses have suggested that both fragmental and tandem duplication contribute to MtTrx gene expansion. Tissue expression analysis has shown that several MtTrx genes may play vital functions in specific tissues, e.g., MtTrx30, MtTrx33 and MtTrx39. Moreover, the expression profiles of MtTrx genes under stresses revealed that 21, 27, and 29 MtTrxs were regulated by cold, drought and salt, respectively, and 11 of these genes responded to all stresses mentioned above (MtTrx3, 13, 17, 18, 22, 24, 25, 31, 32, 33, and 39). Combined with the results of promoter analysis, multiple MtTrx genes were deduced to participate in abiotic stress responses. Results from this study will inspire the future research on functional analysis of MtTrx genes, especially their roles in response to abiotic stress.