Chapter 2 - Role of strigolactones in rhizobiology: Plant-microbe interactions

Abstract

Plants interact with a wide variety of microorganisms that exist belowground in the rhizosphere and aboveground in the phyllosphere in their surrounding environment. The rhizosphere is a soil zone near the plant roots that is home to various organisms, primarily arbuscular mycorrhizal fungi (AMF) and rhizobacteria. Some plant-microbial associations, including antagonistic, amensalism, parasitism, and symbiotic, defend host plants from harmful microbial and nonmicrobial invaders and provide essential nutrients, whereas others negatively impact plants. These interactions have considerable effects on the biomass development of both belowground and aboveground plants, and thus, they play a vital role in plant survival. Understanding microbial association in the rhizosphere and phyllosphere is therefore critical to sustainable agriculture at the field level. Strigolactones (SLs) are a class of phytohormones that play a key role in plant development and adaptability. Strigolactones are assumed to play a crucial role in the plant's association with beneficial microorganisms such as AMF and PGPR. This class of phytohormones, which are generated from carotenoids, has been linked to various physiological processes, including seed germination, plant architecture, photomorphogenesis, nodulation, and physiological responses to environmental stimuli. Prior to root colonization, SL has an influence on AM fungi. SLs secreted from plant roots into the rhizosphere cause several fungal reactions, including germination of spores, growth of hyphal length, respiratory activity, mitosis, gene expression, and the production of chitotetraose and pentaose, all of which stimulate symbiotic responses in the plant. Furthermore, researchers have recently devoted their focus on the importance of SLs in plant-microbe interactions. They have identified that SLs play the main role in the interaction of legumes with nitrogen-fixing rhizobacteria and with disease-causing pathogens. The involvement of SLs in binary plant-microbe interactions has gotten a lot of attention so far. As a result, future research could concentrate on the significance of SLs in plant-microbe interactions for plant growth, balanced nutrition, yield, and quality under abiotic stress. This chapter focuses on the role of SLs in plant interactions with beneficial and harmful species under various environmental conditions.