Endogenous NO-mediated transcripts involved in photosynthesis and carbohydrate metabolism in alfalfa (Medicago sativa L.) seedlings under drought stress.

Alfalfa (Medicago sativa L.) is an important perennial legume and used as a forage crop worldwide, and has extensive resistance to various abiotic stresses. Nitric oxide (NO) plays a critical role in response to external and internal cues to regulate plant growth and development. However, endogenous NO-mediated molecular mechanisms of drought tolerance in alfalfa is poorly understood. To get a deeper insight into the regulate pathway of NO, RNA-Seq was used to profile transcriptome changes of alfalfa seedlings, which were treated with NO scavenger under normal and drought conditions. A total of 1,025 and 3,461 differently-expressed genes (FDR < 0.0001; fold change ≥ 2) were observed while NO absence under normal and drought conditions, respectively. Based on GO enrich and KEGG pathway analysis, we found NO absence induced photosynthesis, carbon fixation in photosynthetic organisms and primary metabolism were significantly up-enriched. Most oxidoreductase, dehydrogenase, reductase and transferase genes were down-regulated in the above processes. Moreover, NO absence restrained chlorophyll biosynthesis and decreased different sugar content. Therefore, this work provides insights into the mechanism that NO-mediated enhanced photosynthesis and carbohydrate metabolism in alfalfa under drought stress.