Abstract
Phytohormones play vital roles in the growth and development of plants as well as in interactions of plants with microbes such as endophytic fungi. The endophytic root-colonizing fungus Piriformospora indica promotes plant growth and performance, increases resistance of colonized plants to pathogens, insects and abiotic stress. Here, we discuss the roles of the phytohormones (auxins, cytokinin, gibberellins, abscisic acid, ethylene, salicylic acid, jasmonates, and brassinosteroids) in the interaction of P. indica with higher plant species, and compare available data with those from other (beneficial) microorganisms interacting with roots. Crosstalks between different hormones in balancing the plant responses to microbial signals is an emerging topic in current research. Furthermore, phytohormones play crucial roles in systemic signal propagation as well as interplant communication. P. indica interferes with plant hormone synthesis and signaling to stimulate growth, flowering time, differentiation and local and systemic immune responses. Plants adjust their hormone levels in the roots in response to the microbes to control colonization and fungal propagation. The available information on the roles of phytohormones in beneficial root–microbe interactions opens new questions of how P. indica manipulates the plant hormone metabolism to promote the benefits for both partners in the symbiosis.
Highlights
Growth and yield benefits are largely attributed to the production of the phytohormones indole-3-acetic acid (IAA), CK, and GA, whereas enhanced stress tolerance is often explained by a systemic resistance response involving ABSCISIC ACID (ABA), ET, salicylic acid (SA), and jasmonates, and their interactions with P. indica have been reported recently (Varma et al, 2012; Gill et al, 2016)
These results clearly demonstrate the involvement of auxin in the symbiotic interaction of various plant species with P. indica, the source of the phytohormone and how it is generated and active remained unclear, until Hilbert et al (2012) showed that indole derivative production by P. indica is not required for growth promotion but for biotrophic colonization of barley roots
The mechanism of drought and salt tolerance mediated by fungi in plants involves the action of CK (Miller, 1974), ABA (Nishiyama et al, 2011), and fungal 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase to utilize ACC (Viterbo et al, 2010)
Summary
Zhang W (2018) Role of Phytohormones in Piriformospora indica-Induced Growth Promotion and Stress Tolerance in Plants: More. Phytohormones play vital roles in the growth and development of plants as well as in interactions of plants with microbes such as endophytic fungi. P. indica interferes with plant hormone synthesis and signaling to stimulate growth, flowering time, differentiation and local and systemic immune responses. Plants adjust their hormone levels in the roots in response to the microbes to control colonization and fungal propagation. The available information on the roles of phytohormones in beneficial root–microbe interactions opens new questions of how P. indica manipulates the plant hormone metabolism to promote the benefits for both partners in the symbiosis
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