ARS | Publication request: Endophyte-mediated adjustments in host morphology and physiology and effects on host fitness traits in grasses

Submitted to: Fungal Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 2, 2011
Publication Date: August 2, 2011
Citation: Torres, M.S., White, J.F., Zhang, X., Hinton, D.M., Bacon, C.W. 2011. Endophyte-mediated adjustments in host morphology and physiology and effects on host fitness traits in grasses. Fungal Ecology. 5(2012):322-330. DOI:10.1016/j.funeco.2011.05.006.

Interpretive Summary: Fungal endophyte of plants, particularly grasses, are tolerant of several stresses from the environment, including drought, insect pest and animal predations. Scientists from Rutger University and ARS, the Toxicology and Mycotoxin Research Unit, Russell Research Center, developed a hypothesis to determine the role oxidative stress might play in both tolerance to stresses and the interaction of the two organisms. The question asked is why does a plant allow a fungus to grow within its tissue consuming plant produced nutrents at the apparent expense of the plant? The answer is complex and suggestive of signaling from the plant as well as from the fungus in highly coordinated physiological levels of expression. Data and evidence is presented to indicate that the fungal endophyte produces protective chemical class of oxygen, called reactive oxygen species, which protect the plants particularly from other fungal pest that act along with auxins secreted both by the plant and the fungal endophyte to produce a highly interactive system protecting the plant from cell death while stimulating it into a vigerous growth pattern. This interaction is also important in maintaining the interaction between the fungus and the plant. The result is a highly coordinated mutualistic associations whithout which the grass cannot survive.

Technical Abstract: Endophytic fungi have been shown to increase tolerance of hosts to biotic and abiotic stresses and in some cases alter growth and development of plants. In this article we evaluate some effects that clavicipitaceous endophytes have on development and physiology of plant tissues. We postulate that oxidative stress protection is the fundamental underlying benefit conferred by many endophytes, accounting for frequently observed enhanced disease resistance, drought tolerance, heavy metal tolerance and tolerance to numerous additional oxidative stresses. We hypothesize that endophyte-mediated oxidative stress protection of the host is the result of at least two processes, including: 1) secretion of reactive oxygen species (ROS) from endophytic mycelia into plant cells; and 2) secretion of auxin from endophytic mycelia into plant cells. Both processes result in an increase in ROS in plant tissues; and stimulate plant tissues to increase activities of antioxidant systems. Auxin is suggested to function in suppression of plant cell death and may be important in maintaining the endophyte-plant symbiosis.