Trichoderma harzianum Enhances Antioxidant Defense of Tomato Seedlings and Resistance to Water Deficit

Abstract

Some plant-symbiotic strains of the genus Trichoderma colonize roots and induce profound changes in plant gene expression that lead to enhanced growth, especially under biotic and abiotic stresses. In this study, we tested the hypothesis that one of the protective mechanisms enhanced by T. harzianum T22 colonization is the antioxidant defense mechanism. Having established that strain T22 modulates the expression of the genes encoding antioxidant enzymes, the status of antioxidant defense of tomato seedlings in response to colonization by T22 and water deficit was investigated. Total ascorbate or glutathione levels were not affected by either stimuli, but under water deficit, antioxidant pools became more oxidized (lower ratios of reduced to oxidized forms), whereas colonized plants maintained redox state as high as or higher than unstressed and untreated plants. The enhanced redox state of colonized plants could be explained by their higher activity of ascorbate and glutathione-recycling enzymes, higher activity of superoxide dismutase, catalase, and ascorbate peroxidase, in both root and shoot throughout the experiment. Similar enzymes were induced in uncolonized plants in response to water-deficit stress but to a lower extent when compared with colonized plants. This orchestrated enhancement in activity of reactive oxygen species (ROS)-scavenging pathways in colonized plants in response to stress supports the hypothesis that enhanced resistance of colonized plants to water deficit is at least partly due to higher capacity to scavenge ROS and recycle oxidized ascorbate and glutathione, a mechanism that is expected to enhance tolerance to abiotic and biotic stresses.

Adaptive Soil Management: A Tool for Plant Fitness in Stressful Environment Through Microbial Integrity

“…Drought tolerant rhizobacteria are capable of synthesizing ROS scavenging enzyme, especially under drought stress and increase photosynthetic efficiency and thus, helping the plants to cope with drought stress. Similar alterations in antioxidative capacity by stress-alleviating microorganisms have been reported earlier (Wang et al 2012;Mastouri et al 2012). ROS detoxification enzyme is an important microbial trait for screening drought stress alleviating potential microorganisms.…”

“…Superoxide (O 2 − ) and hydrogen peroxide (H 2 O 2 ) are other two species of antioxidants found in plant under drought stress. Rhizobacteria by virtue of elaborating superoxide dismutase (SOD) (EC 1.15.1.1) and catalase (CAT) (EC 1.11.1.6) scavenge those antioxidants and help the plant to survive in restricted moisture condition (Mastouri et al 2012).…”

Trichoderma Research in the Genome Era

“…However, the ability of these fungi to sense, invade, and destroy other fungi has been the major driving force behind their commercial success as biopesticides (more than 60% of all registered biopesticides are Trichoderma-based) (136). These fungi not only protect plants by killing other fungi and certain nematodes but induce resistance against plant pathogens, impart abiotic stress tolerance, improve plant growth and vigor, solubilize plant nutrients, and bioremediate heavy metals and environmental pollutants (53,78,81,126). In addition, this genus comprises fungi that produce secondary metabolites of clinical significance and enzymes with widespread industrial application.…”

Identifying Beneficial Qualities of Trichoderma parareesei for Plants

“…The biocontrol mechanisms are based on the production of antibiotics (2,3) and/or hydrolytic enzymes as well as competition for nutrients (4). In addition, Trichoderma strains are also able to stimulate defense responses in plants, inducing resistance to biotic and abiotic stresses, and to promote plant growth (5)(6)(7). Several studies have reported the responses of plants to the presence of a rootcolonizing Trichoderma biocontrol strain (8)(9)(10)(11)(12), and investigations describing the Trichoderma transcriptomic changes elicited by plants using macroarray (13,14) and microarray (15,16) analyses have been performed with biocontrol species.…”