Endophytic fungi as partners in a holistic approach to enhance plant growth and stress tolerance for sustainable agriculture

Plants mutually associate with different taxonomic groups of endophytic fungi. Endophytic fungi can promote plant growth through increased micronutrient acquisition, nitrogen uptake, activity of proton pumps, shoot branching, leaf number, root development and hair formation, metabolism, anti-insect activity, and suppressing plant cell death. They produce volatile organic compounds with a wide range of activities. Endophytic fungi induce plant immune responses to fight against viruses. Plants defend themselves against herbivores through salicylic acid (SA) and jasmonic acid (JA) signaling, regulated by endophytic fungi. They can improve growth under arsenic stress by modulating anti-oxidative enzymes and reducing mobilization from root to shoot and reproductive organs. Endophytic fungi reduce the translocation of arsenic, cadmium, and chromium to the upper parts of plants by chelating them and producing indole-3-acetic acid and gibberellic acid to combat toxic metal and metalloid stress. The molecular mechanisms employed by a taxonomically diverse group of endophytic fungi for conferring toxic metal and metalloid tolerance and enhancing plant growth are discussed.