title: Rice phenylalanine ammonia-lyase gene OsPAL4 is associated with broad spectrum disease resistance.
abstract: Most agronomically important traits, including resistance against pathogens, are governed by quantitative trait loci (QTL). QTL-mediated resistance shows promise of being effective and long-lasting against diverse pathogens. Identification of genes controlling QTL-based disease resistance contributes to breeding for cultivars that exhibit high and stable resistance. Several defense response genes have been successfully used as good predictors and contributors to QTL-based resistance against several devastating rice diseases. In this study, we identified and characterized a rice (Oryza sativa) mutant line containing a 750 bp deletion in the second exon of OsPAL4, a member of the phenylalanine ammonia-lyase gene family. OsPAL4 clusters with three additional OsPAL genes that co-localize with QTL for bacterial blight and sheath blight disease resistance on rice chromosome 2. Self-pollination of heterozygous ospal4 mutant lines produced no homozygous progeny, suggesting that homozygosity for the mutation is lethal. The heterozygous ospal4 mutant line exhibited increased susceptibility to three distinct rice diseases, bacterial blight, sheath blight, and rice blast. Mutation of OsPAL4 increased expression of the OsPAL2 gene and decreased the expression of the unlinked OsPAL6 gene. OsPAL2 function is not redundant because the changes in expression did not compensate for loss of disease resistance. OsPAL6 co-localizes with a QTL for rice blast resistance, and is down-regulated in the ospal4 mutant line; this may explain enhanced susceptibility to Magnoporthe oryzae. Overall, these results suggest that OsPAL4 and possibly OsPAL6 are key contributors to resistance governed by QTL and are potential breeding targets for improved broad-spectrum disease resistance in rice.
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, 80523-1177, USA.
authors.forename: Bradley W
authors.initials: BW
authors.lastname: Tonnessen
authors.forename: Patricia
authors.initials: P
authors.lastname: Manosalva
authors.forename: Jillian M
authors.initials: JM
authors.lastname: Lang
authors.forename: Marietta
authors.initials: M
authors.lastname: Baraoidan
authors.forename: Alicia
authors.initials: A
authors.lastname: Bordeos
authors.forename: Ramil
authors.initials: R
authors.lastname: Mauleon
authors.forename: James
authors.initials: J
authors.lastname: Oard
authors.forename: Scot
authors.initials: S
authors.lastname: Hulbert
authors.forename: Hei
authors.initials: H
authors.lastname: Leung
authors.forename: Jan E
authors.initials: JE
authors.lastname: Leach
mesh_terms: D060467:Disease Resistance / Q000235:genetics / Q000502:physiology; D005091:Exons; D015870:Gene Expression; D017343:Genes, Plant; D020082:Magnaporthe / Q000472:pathogenicity; D005810:Multigene Family; D012275:Oryza / Q000201:enzymology* / Q000235:genetics* / Q000502:physiology; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics*; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology / Q000517:prevention & control*; D010940:Plant Proteins / Q000235:genetics*; D040641:Quantitative Trait Loci; D036226:Seedlings / Q000235:genetics; D017384:Sequence Deletion
chemical_list: D010940:Plant Proteins; D010650:Phenylalanine Ammonia-Lyase