Resistance of rice to the blast fungus Magnaporthe grisea depends on specific interactions controlled by fungal avirulence genes and their corresponding plant resistance genes. The avirulence gene ACE1 that interacts with the rice resistance gene Pi33 encodes a combined polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS), a novel type of eukaryotic enzyme involved in the biosynthesis of an as yet unidentified secondary metabolite. Comparison of ACE1 to known fungal PKS shows that it is related to LNKS from Aspergillus terreus, involved in the biosynthesis of lovastatin. ACE1 is expressed exclusively in penetrating appressoria. High turgor of the appressorial cell appears to be required but not sufficient for the induction of ACE1 expression. Since Ace1p is localized in the cytoplasm of the appressorium and the enzymatic function of Ace1p required for avirulence, we conclude that the signal recognized by resistant rice is not Ace1p itself, but the secondary metabolite produced by Ace1p. Sequence analysis of the genomic region adjacent to ACE1 revealed a cluster of genes potentially involved in secondary metabolism. Several of these appear to be co-regulated withACE1. Our current research focuses on two aspects: identification of the common regulator of the ACE1 gene cluster and whether the entire gene cluster is involved in avirulence.
Fungal Genet. Newsl. 50 (Supl):abstract
Full conference title:
22nd Fungal Genetics Conference
- Fungal Genetics Conference 22nd (2001)