Reduction of abscisic acid levels or inhibition of abscisic acid signaling in rice during the early phase of Magnaporthe oryzae infection decreases its susceptibility to the fungus

Exogenous application of abscisic acid (ABA) compromises rice resistance to Magnaporthe oryzae. Here, we analyzed the influence of ABA level/signaling on defense responses of rice plants during the early phase of M. oryzae infection. Decreased ABA levels or inhibition of ABA signaling by expressing OsA-BA8ox1 or OsABI(G-to-A) genes before, but not after, M. oryzae inoculation decreased lesion numbers. Microscopic observation showed increased fungal invasion into the cells of rice transformants, accompanied by enhanced autofluorescence accumulation and decreased callose formation. These results indicate that ABA promotes M. oryzae infection of rice during early stages of infection. (C) 2011 Elsevier Ltd. All rights reserved.