Mutualistic association of Paecilomyces formosus LHL10 offers thermotolerance to Cucumis sativus

Abstract

We investigated in this study the influence of an endophytic fungus, Paecilomyces formosus LHL10, on the thermotolerance of cucumber (Cucumis sativus) upon exposure to high (38°C) and low (8°C) temperature stresses. The results showed that endophyte-inoculated plants had significantly higher plant growth attributes under high-temperature stress. However, they were either low or insignificant in non-inoculated control and inoculated plants with 8°C treatments. Lower stress-promulgated water deficit and cellular membrane damage were observed in endophyte-treated plants after 38°C treatment than in control plants under 8°C stress. Total polyphenol, reduced glutathione, and lipid peroxidation activities were reduced in endophyte-associated plants after exposure to 38°C as compared with control and 8°C-treated plants. The concentration of saturated fatty acids (palmitic-C16:0; stearic-C18:0) was lower in endophyte-treated plants with or without low-temperature stress, but after 8°C treatment increased compared with controls. Unsaturated fatty acids (oleic-C18:1; linoleic-C18:2; linolenic-C18:3 acids) were similar at normal conditions; however, at 38°C, C18:2 and C18:3 were decreased, and C18:1 was increased in endophyte-treated plants compared with controls, while the inverse relationship was found at 8°C. Low levels of abscisic acid in P. formosus-associated plants after 38°C treatments revealed stress tolerance compared with control and 8°C-treated plants. In contrast, salicylic acid was pronounced in endophyte-treated plants after low-temperature stress as compared to other treatments. The results provide evidence that the response to P. formosus association was beneficial at normal growth temperature and had varying effects in response to temperature stress.

Mutualistic fungal endophytes produce phytohormones and organic acids that promote japonica rice plant growth under prolonged heat stress

“…Growth promotion may be attributed to the ability of P. formosus LWL1 to produce multiple important secondary metabolites (Khan et al, 2012;Waqas et al, 2014). Current results are in strong agreement with the findings of Khan et al (2011), who reported the ability of the same fungus, P. formosus LHL10, to induce thermo-tolerance.…”

“…Plant association with phytohormones produced by endophytes has also been helpful in mitigating abiotic and biotic stresses (Khan et al, 2012;Waqas et al, 2014a;2014b). Endophytes benefit host plants in a number of ways by improving uptake of nutrients and water, water-use efficiency, endogenous hormone levels, and survivability competition without causing any harm (Khan et al, 2012). This important plantmicrobe association (Khan et al, 2012;Higgins et al, 2014;Waqas et al, 2014b) is the basis of our study.…”

“…The metabolic network consists of characterized enzymes in specified tissues and organs. Plant network models are mediated by microorganisms such as bacteria and fungi, known as "plantmicrobe" interactions (Khan et al, 2012). These plant-microbe interactions can provide regulatory dynamics towards plant growth in biotic and abiotic stresses.…”

“…Moreover, exogenous application of these phytohormones has been proven to alleviate heat stress (Bita and Gerats, 2013;Hasanuzzaman et al, 2013;Claeys et al, 2014). Plant association with phytohormones produced by endophytes has also been helpful in mitigating abiotic and biotic stresses (Khan et al, 2012;Waqas et al, 2014a;2014b). Endophytes benefit host plants in a number of ways by improving uptake of nutrients and water, water-use efficiency, endogenous hormone levels, and survivability competition without causing any harm (Khan et al, 2012).…”

“…Endophytes benefit host plants in a number of ways by improving uptake of nutrients and water, water-use efficiency, endogenous hormone levels, and survivability competition without causing any harm (Khan et al, 2012). This important plantmicrobe association (Khan et al, 2012;Higgins et al, 2014;Waqas et al, 2014b) is the basis of our study. We hypothesized that secondary metabolites produced by fungal endophyte symbiosis will not only maintain but also promote rice plant growth under prolonged heat stress conditions.…”