G-PROTEIN ALPHA-SUBUNIT GENES CONTROL GROWTH, DEVELOPMENT, AND PATHOGENICITY OF MAGNAPORTHE-GRISEA

Three G protein alpha subunit genes have been cloned and characterized from Magnaporthe grisea: magA is very similar to CPG-2 of Cryphonectr ia parasitica; magB is virtually identical to CPG-1 of Cryphonectria p arasitica, to gna1 of Neurospora crassa, and to fadA of Emericella nid ulans; and magC is most similar to gna2 of Neurospora crassa, Homologo us recombination resulting in targeted deletion of magA had no effect on vegetative growth, conidiation, or appressorium formation, Deletion of magC reduced conidiation, but did not affect vegetative growth or appressorium formation, However, disruption of magB significantly redu ced vegetative growth, conidiation, and appressorium formation, magB(- ) transformants, unlike magA(-) and magC(-) transformants, exhibited a reduced ability to infect and colonize susceptible rice leaves, G pro tein alpha subunit genes are required for M. grisea mating, magB(-) tr ansformants failed to form perithecia, whereas magA(-) and magC(-) tra nsformants did not produce mature asci, These results suggest that G p rotein alpha subunit genes are involved in signal transduction pathway s in M. grisea that control vegetative growth, conidiation, conidium a ttachment, appressorium formation, mating, and pathogenicity.