title: An oleic acid-mediated pathway induces constitutive defense signaling and enhanced resistance to multiple pathogens in soybean.
abstract: Stearoyl-acyl carrier protein-desaturase (SACPD)-catalyzed synthesis of oleic acid (18:1) is an essential step in fatty acid biosynthesis. Arabidopsis mutants (ssi2) with reduced SACPD activity accumulate salicylic acid (SA) and exhibit enhanced resistance to multiple pathogens. We show that reduced levels of 18:1 induce similar defense-related phenotypes in soybean. A Bean pod mottle virus (BPMV)-based vector was employed to effectively silence soybean SACPDs. The silenced plants contained reduced 18:1 and increased stearic acid, developed spontaneous cell death lesions, increased SA accumulation, and constitutively expressed pathogenesis-related genes. These plants also expressed elevated levels of resistance-like genes and showed resistance to bacterial and oomycete pathogens. Exogenous application of glycerol induced similar phenotypes, mimicking the effect of silencing SACPDs in healthy soybean plants. Overexpression of a soybean SACPD increased 18:1 levels in ssi2 but not in wild-type Arabidopsis plants, suggesting that the soybean enzyme was under feedback regulation similar to that of the Arabidopsis isozymes. These results suggest that soybean and Arabidopsis respond similarly to 18:1-derived cues by inducing a novel broad-spectrum resistance-conferring pathway, even though they differ significantly in their lipid biosynthetic pathways. We also demonstrate the efficacy of BPMV-induced gene silencing as a tool for functional studies in soybean.
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, Kentucky 40546, USA. apkach2@uky.edu
authors.forename: Aardra
authors.initials: A
authors.lastname: Kachroo
authors.forename: Da-Qi
authors.initials: DQ
authors.lastname: Fu
authors.forename: Wendy
authors.initials: W
authors.lastname: Havens
authors.forename: DuRoy
authors.initials: D
authors.lastname: Navarre
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kachroo
authors.forename: Said A
authors.initials: SA
authors.lastname: Ghabrial
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000382:microbiology / Q000469:parasitology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020868:Gene Silencing; D005822:Genetic Vectors / Q000235:genetics; D005990:Glycerol / Q000494:pharmacology; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D019301:Oleic Acid / Q000378:metabolism*; D009868:Oomycetes / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D044224:Pseudomonas syringae / Q000254:growth & development; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics* / Q000502:physiology; D013025:Glycine max / Q000235:genetics* / Q000382:microbiology / Q000469:parasitology
chemical_list: D010940:Plant Proteins; D020033:Protein Isoforms; D019301:Oleic Acid; D006899:Mixed Function Oxygenases; C018747:acyl-(acyl-carrier-protein)desaturase; D005990:Glycerol