Role of trehalose in plant–rhizobia interaction and induced abiotic stress tolerance

Trehalose, an osmoprotectant, acts as a source of carbon and energy accumulated in late-logarithmic and stationary phases under microaerophilic conditions inside the nodule of the rhizobium-legume association and in the free-living stage. Among five different biosynthesis pathways, ots AB and MOTS pathways are the predominant pathways utilized by rhizobia to synthesize trehalose in almost all legume interactions. However, the trehalose concentration inside the symbiotic system is determined by trehalase, phosphorylase, and hydrolase enzymes, which keep the concentration in the desired range. Its accumulation plays a vital role as an osmoprotectant for the survivability of the rhizobium under free-living and symbiotic conditions and is involved in the alleviation of abiotic and biotic stresses in the plants. Trehalose synthesis triggers during the onset of symbiotic relationships and has a positive role in nodulation parameters under abiotic stresses. Additionally, the Trehalose-6-phosphate plays a role in sugar transport and the availability of sucrose and starch or sugar partitioning. Transferring trehalose synthesizing genes of the biosynthetic pathways into plant systems or bacterial systems could be a game-changer for the abiotic stress tolerance in plants and microbial systems. In this chapter, we discussed the trehalose biosynthesis pathways in plants and rhizobia. Provided the role of rhizobial trehalose in abiotic and biotic stress protectants and legume-rhizobia interaction for higher nodulation and nitrogen fixation. The role of trehalase in maintaining trehalose concentration inside legume and rhizobia and genetic alterations for expression of trehalose synthesis for abiotic stress tolerance are also discussed.