The rhizosphere is a dynamic environment in which the interaction and communication between plants and soil microbes are the basis of the survival of both types of organisms (Lundberg et al. 2012; Bailly et al. 2014). Many studies have demonstrated that plant probiotics improve host plant growth and root system development through secretion- or volatile organic compound (VOC)-mediated increases in the uptake of nutrients, changes in phytohormone equilibrium or the triggering of plant systemic resistance, and the auxin signaling pathway plays a central role in these processes (Ryu et al. 2003; Felten et al. 2009; Contreras-Cornejo et al. 2009; Bulgarelli et al. 2012; Zamioudis et al. 2013; Bailly et al. 2014).
VOCs act as info-chemicals that mediate short- and long-distance organismal interactions due to their ability to travel in the atmosphere and in liquid and porous soil (Bitas et al. 2013). Many studies have indicated that microbial VOCs can act as regulators of plant growth and stress resistance (Contreras-Cornejo et al. 2009; Patel et al. 2008; Buée et al. 2009; Saunders et al. 2010; Porras-Alfaro and Bayman 2011; Zamioudis et al. 2013; Bennett et al. 2013; Bailly et al. 2014). As one of the major VOCs produced by Bacillus amyloliquefaciens, B. subtilis, and Pseudomonas chlororaphis, 2,3-butanediol promotes plant growth and development in Arabidopsis and tobacco (Ryu et al. 2003; Han et al. 2006; Farag et al. 2006).
Several mushroom VOCs have been identified and proved to modulate plant growth and development (Kishimoto et al. 2007; Splivallo et al. 2007; Choi et al. 2010a, b, 2014; Kawagishi 2018, 2019). For example, 3-octenol, also known as mushroom alcohol, is a VOC produced by fungi that can induce the expression of genes involved in jasmonic acid/ethylene-dependent pathogen or wound defense signaling pathways (Kishimoto et al. 2007). Splivallo et al. (2007) suggested that 3-octenol negatively affects plant growth by modifying the oxidative metabolism of plants. 2-azahypoxanthine (AHX), isolated from the fairy-ring-forming mushroom fungus Lepista sordida, is the first identified potential ‘fairy chemical’ that forms fairy ring (Choi et al. 2010a, b). Exogenous AHX improves plant growth and increases nitrogen uptake in rice. However, AHX do not affect cell proliferation and its promotive effect on plant growth is independent of cytokinin and auxin (Choi et al. 2010a, b). In addition to AHX, another fairy chemical, imidazole-4-carboxamide (ICA) was also isolated from Lepista sordida. AHX is converted into 2-aza-8-oxohypoxanthine (AOH) in plants (Choi et al. 2014; Kawagishi 2018, 2019). Further studies indicated that these fairy chemicals endogenously exist in plants and are biosynthesized via a new purine metabolic pathway, and exogenous fairy chemicals improve crop yields (Choi et al. 2014, 2018; Kawagishi 2018, 2019).
Floccularia luteovirens is an edible mushroom fungus that grows widely on the Qinghai-Tibet Plateau. F. luteovirens can form a fairy ring, consisting of a visible green ring composed of mushroom fruiting bodies and a green plant stimulation zone (Xing et al. 2018; Yang et al. 2019), suggesting that the effect of the passage of F. luteovirens produce a particular enhancement of the growth of alpine meadow plants on the Qinghai-Tibet Plateau. However, the underlying physiological and molecular mechanisms of F. luteovirens in modulating plant growth and development remain largely unclear. We speculated that the VOCs produced by F. luteovirens play a role in this effect. To address this hypothesis, we investigated the effects of F. luteovirens VOCs on root system architecture (RSA) using Arabidopsis as study material. Arabidopsis is a model plant species with various of transgenic marker lines and mutants. A lot of studies on the growth, development and stress responses of Arabidopsis have made important contributions to crop stress tolerance and environmental adaptation (Sun et al. 2020). In this study, the effects of F. luteovirens VOCs in modulating auxin distribution and accumulation in root tips, and the changes in metabolic profiling in Arabidopsis seedlings in responses to F. luteovirens VOCs were investigated.
This result was published in Plant and Soil with the title of "The volatile organic compounds of Floccularia luteovirens modulate plant growth and metabolism in Arabidopsis thalianau".
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