Priming by arbuscular mycorrhizal fungi of plant antioxidant enzyme production: A meta-analysis
Priming of antioxidant enzyme production of plants, which can act as a defense against pathogens and other stresses, is an under-appreciated benefit often provided by arbuscular mycorrhizal (AM) fungi. Although numerous experiments have demonstrated this phenomenon, this literature has not been synthesized, and we understand little about the factors that may drive variation in the magnitude of this priming phenomenon. We gathered data from 81 original publications in which antioxidant enzyme production of plants was measured in the presence and absence of AM fungi, including factors that varied among studies, such as the identity of plants and fungi, number of species and genera of fungi, the presence and type of plant stress, the particular enzyme measured, and the plant tissues sampled. We used these data to estimate the average magnitude of the priming effect, and to ask whether these study-level variables explained variation in the magnitude of priming. We found that AM fungi increased plant production of antioxidant enzymes by approximately 16%, regardless of whether the plants were under stress. The identity of plants and fungi, number of species and genera of fungi, and the type of stress did not explain variability in the degree of priming. In the absence of stress, priming was higher for peroxidase enzymes than other enzyme classes, and plant root tissues exhibited greater priming responses than other plant tissues. Our best meta-analysis models had substantial unexplained heterogeneity in effect size among studies, suggesting that additional factors not included in our analyses could help explain variation in priming. Overall, the degree of priming observed here suggests the potential for mycorrhiza-induced resistance to disease to have broader application, including for the improvement of sustainable agriculture.
Lokhandwala A. and Hoeksema J. D. 2019. Priming by arbuscular mycorrhizal fungi of plant antioxidant enzyme production: A meta-analysis. Annual Plant Reviews Online.