Poly-γ-glutamic acid enhanced drought resistance of maize by improving photosynthesis and affecting rhizosphere microbial community

Background: Compared with other abiotic stresses, drought stress is a serious causal factor leading to crop yield reduction. Poly-γ-glutamic acid (γ-PGA), as an environmentally friendly biomacromolecule, plays an important role in plant growth and regulation. Results In this project, the effect of exogenous application of γ-PGA on drought tolerance of maize ( Zea mays . L) and its mechanism were studied. Drought dramatically inhibited the growth and development of maize, but the exogenous application of γ-PGA significantly increased the dry weight of maize and the contents of ABA, soluble sugar, proline, chlorophyll and the photosynthetic rate under severe drought stress. RNAseq data showed that γ-PGA may enhance drought resistance of maize by affecting the expression of ABA biosynthesis and signal transduction related genes, photosynthesis-related genes and other stress-responsive genes, which were also confirmed by RT-PCR and promoter motif analysis. In addition, diversity and structure analysis of rhizosphere soil bacterial community demonstrated that γ-PGA enriched the plant growth promoting bacteria such as Actinobacteria , Chloroflexi , Firmicutes , Alphaproteobacteria and Deltaproteobacteria . Meanwhile, γ-PGA significantly improved roots development, urease activity and ABA contents of maize rhizospheric soil under drought stress. This study emphasized the possibility of using γ-PGA to improve crop drought resistance and soil environment under drought condition and revealed its preliminary mechanism. Conclusions Exogenous application of poly-γ-glutamic acid could significantly enhance the drought resistance of maize by improving photosynthesis, root development and affecting rhizosphere microbial community.