Alleviation of Drought Stress and Metabolic Changes in Timothy (Phleum pratense L.) Colonized with Bacillus subtilis B26

Abstract

Drought is a major limiting factor of crop productivity worldwide and its incidence is predicted to increase under climate change. Drought adaptation of cool-season grasses is thus a major challenge to secure the agricultural productivity under current and future climate conditions. Endophytes are non-pathogenic plant-associated bacteria that can play an important role in conferring resistance and improving plant tolerance to drought. In this study, the effect of inoculation of the bacterial endophyte Bacillus subtilis strain B26 on growth, water status, photosynthetic activity and metabolism of timothy (Phleum pratense L.) subjected to drought stress was investigated under controlled conditions. Under both drought-stress and non-stressed conditions, strain B26 successfully colonized the internal tissues of timothy and had a positive impact on plant growth. Exposure of inoculated plant to a 8-week drought-stress led to significant increase in shoot and root biomass by 26.6 and 63.8%, and in photosynthesis and stomatal conductance by 55.2 and 214.9% respectively, compared to non-inoculated plants grown under similar conditions. There was a significant effect of the endophyte on plant metabolism; higher levels of several sugars, notably sucrose and fructans and an increase of key amino acids such as, asparagine, glutamic acid and glutamine were recorded in shoots and roots of colonized plants compared to non-colonized ones. The accumulation of the non-protein amino acid GABA in shoots of stressed plants and in roots of stressed and unstressed plants was increased in the presence of the endophyte. Taken together, our results indicate that B. subtilis B26 improves timothy growth under drought stress through the modification of osmolyte accumulation in roots and shoots. These results will contribute to the development of a microbial agent to improve the yield of grass species including forage crops and cereals exposed to environmental stresses.

Bacillus subtilis ameliorates water stress tolerance in maize and common bean

“…In wheat, inoculation with B. subtilis induced higher rate of CO 2 assimilation in plants exposed to water stress when compared to non-inoculated and stressed plants (Barnawal et al 2017). Gagné-Bourque et al (2016) observed positive effects on the photosynthetic rate in Timothy plants inoculated with B. subtilis and exposed to water stress. Overall, B. subtilis positively influences photosynthetic activity, being a promoter of water use efficiency in plants (Li et al 2016).…”

“…Among the most well-known PGPR, Bacillus subtilis has received particular attention because of its catabolic versatility and root colonization ability, as well as its capability to produce a large number of enzymes and metabolites that can favor plant growth under biotic and abiotic stress conditions (Gagné-Bourque et al 2016). Indeed, studies have found B. subtilis increasing the photosynthetic capacity of plants through a direct influence on stomatal conductance and cell tolerance to dehydration (Cohen et al 2008;Zhang et al 2008;Li et al 2016).…”

UPLC‐HRMS‐based untargeted metabolic profiling reveals changes in chickpea (Cicer arietinum) metabolome following long‐term drought stress

“…Drought stress leads to the reduction in protein synthesis and an increase in hydrolysis of proteins, endorsing surge in soluble nitrogen compounds such as free amino acids (Farooq et al, 2009;Krasensky & Jonak, 2012). Proline, highly accumulated due to water stress, not only acts as an osmolyte during drought but also acts as a signalling molecule and provides defence against oxidative damage (Cheng et al, 2015;Gagné-Bourque, Bertrand, Claessens, Aliferis, & Jabaji, 2016;Hayat et al, 2012). In cell cytoplasm, it not only stabilizes protein structure but also helps in maintaining cell pH and redox status under severe stress condition by reducing the amount of singlet oxygen present, which causes lipid peroxidation of thylakoid membranes (Alia & Mohanty, 1997;Hammad & Ali, 2014;Hayat et al, 2012;Szabados & Savouré, 2010).…”

Plant root exudation under drought: implications for ecosystem functioning

“…in the soybean rhizosphere; Allard‐Massicotte et al , ). B. subtilis is a beneficial bacterial species that increases drought resistance in Phleum pratense L. by activating osmolyte secretion (Gagné‐Bourque et al , ). Interactions with other rhizosphere bacteria that reduce drought impact have been identified (e.g.…”