AUXIN RESPONSE FACTOR 1 Acts as a Positive Regulator in the Response of Poplar to Trichoderma asperellum Inoculation in Overexpressing Plants

Numerous strains have been reported to be optimal biofertilizers and biocontrol agents with low production costs and environmentally friendly properties. spp. promote the growth and immunity of plants by multiple means. Interfering with the hormonal homeostasis in plants is the most critical strategy. However, the mechanisms underlying plants' responses to remain to be further elucidated. Auxin is the most important phytohormone that regulates almost every aspect of a plant's life, especially the trade-off between growth and defense. The AUXIN RESPONSE FACTOR (ARF) family proteins are key players in auxin signaling. We studied the responses and functions of the gene in a hybrid poplar during its interaction with beneficial . strains using transformed poplar plants with overexpression (on transcription level in this study). We report that is a positive regulator for promoting poplar growth and defense responses, as does . inoculation. also turned out to be a positive stimulator of adventitious root formation. Particularly, the overexpression of induced a 32.3% increase in the height of 40-day-old poplar plants and a 258% increase in the amount of adventitious root of 3-week-old subcultured plant clones. Overexpressed exerted its beneficial functions through modulating the hormone levels of indole acetic acid (IAA), jasmonic acid (JA), and salicylic acid (SA) in plants and activating their signaling pathways, creating similar results as inoculated with . Particularly, in the overexpressing poplar plants, the IAA level increased by approximately twice of the wild-type plants; and the signaling pathways of IAA, JA, and SA were drastically activated than the wild-type plants under pathogen attacks. Our report presents the potential of s as the crucial and positive responders in plants to inducing.