Expression ofMagnaporthe griseaAvirulence GeneACE1Is Connected to the Initiation of Appressorium-Mediated Penetration

Isabelle Fudal, Jérôme Collemare, Heidi U. Böhnert, Delphine Melayah, Marc-Henri Lebrun
2006 Eukaryotic Cell  
Magnaporthe griseais responsible for a devastating fungal disease of rice called blast. Current control of this disease relies on resistant rice cultivars that recognizeM. griseasignals corresponding to specific secreted proteins encoded by avirulence genes. TheM. grisea ACE1avirulence gene differs from others, since it controls the biosynthesis of a secondary metabolite likely recognized by rice cultivars carrying thePi33resistance gene. Using a transcriptional fusion betweenACE1promoter
more » ... P, we showed thatACE1is only expressed in appressoria during fungal penetration into rice and barley leaves, onion skin, and cellophane membranes.ACE1is almost not expressed in appressoria differentiated on Teflon and Mylar artificial membranes.ACE1expression is not induced by cellophane and plant cell wall components, demonstrating that it does not require typical host plant compounds. Cyclic AMP (cAMP) signaling mutants ΔcpkAand Δmac1 sum1-99and tetraspanin mutant Δpls1::hphdifferentiate melanized appressoria with normal turgor but are unable to penetrate host plant leaves.ACE1is normally expressed in these mutants, suggesting that it does not require cAMP signaling or a successful penetration event.ACE1is not expressed in appressoria of thebuf1::hphmutant defective for melanin biosynthesis and appressorial turgor. The addition of hyperosmotic solutes tobuf1::hphappressoria restores appressorial development andACE1expression. Treatments of young wild-type appressoria with actin and tubulin inhibitors reduce both fungal penetration andACE1expression. These experiments suggest thatACE1appressorium-specific expression does not depend on host plant signals but is connected to the onset of appressorium-mediated penetration.
doi:10.1128/ec.00330-05 pmid:17142568 pmcid:PMC1828936 fatcat:cxrmhp5hrncfzel453bpatta5e