Graphene enhances photosynthesis and the antioxidative defense system and alleviates salinity and alkalinity stresses in alfalfa (Medicago sativa L.) by regulating gene expression

Soil salinity and alkalinity are important factors affecting the growth, development, and productivity of alfalfa (Medicago sativa), while nanomaterials could affect the growth and alleviate stress. However, the molecular regulation mechanisms remain largely unknown about how nanoparticle-treated alfalfa responds and adapts to the abiotic stress. We sequenced the transcriptomic changes in graphene-treated leaves under salt and alkali stresses. A total of 19.4 Gb of clean reads were generated by SMRT sequencing including 265 811 CCS and 219 162 FLNC reads, and 12 960 non-redundant transcripts were obtained. RNA-seq analysis revealed 930, 1114 and 880 DEGs in leaves treated with graphene, graphene–salt and graphene–alkali, respectively, among which hundreds of genes are involved in hormonal signaling, photosynthesis, respiration, and transcriptional regulation pathways. Notably, specific differential gene expression patterns such as the antioxidant defense system and photosynthesis may rapidly confer abiotic tolerance in alfalfa leaves treated with graphene. Moreover, the physiological changes were consistent with the complex transcript profiles of the genes involved, suggesting that photosynthesis and the antioxidant defense mechanism played a critical role in reacting to salt and alkali stresses. These observations provide a full characterization of gene transcription and promote the understanding of the molecular mechanisms of nanoparticle-treated alfalfa adaptation to abiotic stresses.