Mitigating abiotic stress: microbiome engineering for improving agricultural production and environmental sustainability.

MAIN CONCLUSION: The responses of plants to different abiotic stresses and mechanisms involved in their mitigation are discussed. Production of osmoprotectants, antioxidants, enzymes and other metabolites by beneficial microorganisms and their bioengineering ameliorates environmental stresses to improve food production. Progressive intensification of global agriculture, injudicious use of agrochemicals and change in climate conditions have deteriorated soil health, diminished the microbial biodiversity and resulted in environment pollution along with increase in biotic and abiotic stresses. Extreme weather conditions and erratic rains have further imposed additional stress for the growth and development of plants. Dominant abiotic stresses comprise drought, temperature, increased salinity, acidity, metal toxicity and nutrient starvation in soil, which severely limit crop production. For promoting sustainable crop production in environmentally challenging environments, use of beneficial microbes has emerged as a safer and sustainable means for mitigation of abiotic stresses resulting in improved crop productivity. These stress-tolerant microorganisms play an effective role against abiotic stresses by enhancing the antioxidant potential, improving nutrient acquisition, regulating the production of plant hormones, ACC deaminase, siderophore and exopolysaccharides and accumulating osmoprotectants and, thus, stimulating plant biomass and crop yield. In addition, bioengineering of beneficial microorganisms provides an innovative approach to enhance stress tolerance in plants. The use of genetically engineered stress-tolerant microbes as inoculants of crop plants may facilitate their use for enhanced nutrient cycling along with amelioration of abiotic stresses to improve food production for the ever-increasing population. In this chapter, an overview is provided about the current understanding of plant-bacterial interactions that help in alleviating abiotic stress in different crop systems in the face of climate change. This review largely focuses on the importance and need of sustainable and environmentally friendly approaches using beneficial microbes for ameliorating the environmental stresses in our agricultural systems.

Interkingdom signaling in plant-rhizomicrobiome interactions for sustainable agriculture.

The rhizosphere is a complex ecosystem around plant roots that comprises an integrated network of plant roots, the microbiome and soil. Wide spread communication between prokaryotes and eukaryotes occurs within this integrated network via a complex set of signal molecules secreted during both beneficial and harmful interactions. Intra- and inter-species communication among microbes occurs through various signal molecules that coordinate and control the behaviours of microorganisms in mixed communities. In addition, interkingdom signal exchange between plants and microbes occurs through the release of root exudates from the host plants. The diverse chemical substances released in root exudates affect the structural and physical heterogeneity of the soil. Moreover, chemical compounds released in root exudates trigger various signaling pathways in microbial populations that influence rhizosphere biology. Therefore, deciphering the language of interkingdom communication and understanding the mechanisms involved is innovative and promising approach for improving crop production in sustainable agriculture. This chapter describes briefly the shaping of the rhizomicrobiome in response to released root exudates. Moreover, predicting and controlling the microbiome structure and its function in the rhizosphere by understanding of rhizomicrobiome communication through different secreted compounds will allow us to better harness beneficial plant-microbe interactions. The recent progress in understanding interkingdom communication and interactions between plants and microbes is discussed in relation to plant growth, gene expression, nutrient uptake and resistance to pests and diseases along with mitigation of abiotic stresses in plants to improve plant ecosystem productivity for sustainable agriculture.