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

Background: Compared with other abiotic stresses, drought stress causes serious crop yield reductions. Poly-gamma-glutamic acid (gamma-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 gamma-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 gamma-PGA significantly increased the dry weight of maize, the contents of ABA, soluble sugar, proline, and chlorophyll, and the photosynthetic rate under severe drought stress. RNA-seq data showed that gamma-PGA may enhance drought resistance in maize by affecting the expression of ABA biosynthesis, signal transduction, and photosynthesis-related genes and other stress-responsive genes, which was also confirmed by RT-PCR and promoter motif analysis. In addition, diversity and structure analysis of the rhizosphere soil bacterial community demonstrated that gamma-PGA enriched plant growth promoting bacteria such as Actinobacteria, Chloroflexi, Firmicutes, Alphaproteobacteria and Deltaproteobacteria. Moreover, gamma-PGA significantly improved root development, urease activity and the ABA contents of maize rhizospheric soil under drought stress. This study emphasized the possibility of using gamma-PGA to improve crop drought resistance and the soil environment under drought conditions and revealed its preliminary mechanism. Conclusions: Exogenous application of poly-gamma-glutamic acid could significantly enhance the drought resistance of maize by improving photosynthesis, and root development and affecting the rhizosphere microbial community.

Automated summary

This study investigated the effect of exogenous application of gamma-PGA on drought tolerance of maize and its mechanism. The results showed that gamma-PGA significantly increased the dry weight, ABA, soluble sugar, proline, and chlorophyll contents, as well as the photosynthetic rate of maize under severe drought stress. The study also demonstrated that gamma-PGA improved root development and affected the rhizosphere microbial community. This research revealed the potential of using gamma-PGA to enhance crop drought resistance.