Characterizing roles for lactate metabolism in rice blast disease: new insights into post-penetrative host infection strategies by Magnaporthe oryzae
R. ROCHA (1) (1) University of Nebraska-Lincoln, U.S.A.

Magnaporthe oryzae is the most important pathogen of rice. At the start of the infection, the fungus breaches the plant cuticle by using a specialized structure, called an appressorium. In this stage, lipid metabolism is required for the development of the appressoria and penetration. Once in the host cell lumen, M. oryzae re-programs its metabolic machinery to utilize glucose via the pentose phosphate pathway (PPP) in order to fuel NADPH production. Little is known about the fate of glucose after the PPP, and it is not known how TCA cycle intermediates are replenished during rapid growth in planta. By using transcriptional analysis, we demonstrate that genes encoding two lactate dehydrogenases, LDH3 and LDH4, are up-regulated compared to LDH1, LDH2, and LDH5 during biotrophic growth in planta. Targeted gene deletion studies demonstrate that LDH3 is a key enzyme for lactate production and secretion in axenic shakes. LDH3 and LDH4 were not required for growth on minimal media, sporulation, germination or appressorium formation. Moreover, Dldh3 and Dldh4 appressoria were fully functional and penetrated rice epidermal cells like wild type. However, Dldh3 mutant strains were reduced for cell-to-cell movement, compared to wild type, inside host cells indicating LDH3-dependent lactate metabolism is critical for the early biotrophic stage of infection. These results thus provide new information on the metabolic strategies employed by M. oryzae to successfully colonize host cells.

Abstract Number: P7-203
Session Type: Poster