Analysis of Aldo–Keto Reductase Gene Family and Their Responses to Salt, Drought, and Abscisic Acid Stresses in Medicago truncatula

Salt and drought stresses are two primary abiotic stresses that inhibit growth and reduce the activity of photosynthetic apparatus in plants. Abscisic acid (ABA) plays a key role in abiotic stress regulation in plants. Some aldo–keto reductases (AKRs) can enhance various abiotic stresses resistance by scavenging cytotoxic aldehydes in some plants. However, there are few comprehensive reports of plant AKR genes and their expression patterns in response to abiotic stresses. In this study, we identified 30 putative AKR genes from Medicago truncatula. The gene characteristics, coding protein motifs, and expression patterns of these MtAKRs were analyzed to explore and identify candidate genes in regulation of salt, drought, and ABA stresses. The phylogenetic analysis result indicated that the 52 AKRs in Medicago truncatula and Arabidopsis thaliana can be divided into three groups and six subgroups. Fifteen AKR genes in M. truncatula were randomly selected from each group or subgroup, to investigate their response to salt (200 mM of NaCl), drought (50 g·L(−1) of PEG 6000), and ABA (100 µM) stresses in both leaves and roots. The results suggest that MtAKR1, MtAKR5, MtAKR11, MtAKR14, MtAKR20, and MtAKR29 may play important roles in response to these stresses.