Metabolic engineering of fungal secondary metabolism in plants for stress tolerance

Fungi synthesize many secondary metabolites which play a vital role in their adaptation to changing environments and during biological stresses such as drought, temperature, salt, etc. Major types of secondary metabolites, including isoprenoids, carotenoids, and flavonoids can tolerate stress. Secondary metabolite formation and deposition increased significantly under abiotic stress to adapt to harsh stress conditions, revealing a close relationship between secondary metabolite deposition and plant tolerance to stresses. Moreover, secondary metabolite formation and deposition can be manipulated to improve plants' resistance to stress. To influence the synthesis and deposition of secondary metabolic compounds, such as isoprenoids, carotenoids, and flavonoids, as well as plant hormones like abscisic acid, metabolic engineering methods have been confirmed to be very effective. In recent years, metabolic engineering of secondary metabolic pathways has been effectively applied to tobacco (Nicotiana tabacum), alfalfa (Medicago sativa L.), brassica (Brassica oleracea), sweet potato (Ipomoea batatas), and Arabidopsis (Arabidopsis thaliana) to assign stress tolerance. The current chapter focuses on the roles of stress-protecting secondary metabolites. It explains the progress and prospects of metabolic engineering of fungal secondary metabolite biosynthesis to improve plant stress tolerance.