Bhuiyan, Nazmul H. , Wei, Yangdou , King, John .
Expression profiling and gene silencing reveal that monolignol biosynthesis plays a critical role in epidermal defense in wheat in response to powdery mildew attack.
Lignin is a complex polymer of hydroxylated and methoxylated phenylpropane units, linked via oxidative coupling. It is important for structural integrity of the plant cell wall. For a long time, it has been believed that lignin accumulation is directly involved in cell wall apposition formation during cereal defense responses to powdery mildew invasion. However, no genetic evidence for this has been shown so far. We isolated a complete set of genes (TmPAL, TmC3H, TmCOMT, TmF5H, Tm4CL, TmCCoAOMT, TmCCR and TmCAD encoding phenylalanine ammonia-lyase, p-coumarate 3-hydroxylase, caffeic acid O-methyltransferase, ferulate 5-hydroxylase, 4-hydroxycinnamoyl-CoA ligase, caffeoyl-CoA O-methyltransferase, cinnamoyl-CoA reductase and cinnamoyl-alcohol dehydrogenase, respectively) involved in monolignol biosynthesis from a cDNA library derived from the epidermis of diploid wheat infected with Blumeria graminis f. sp tritici (Bgt) to investigate the regulation of monolignol biosynthesis during powdery mildew infection. We found differential expression patterns for these genes in susceptible and resistant plants after Bgt infection. Expression of TmPAL, TmCOMT, TmF5H, TmCCoAOMT and TmCAD were highly induced, particularly in epidermis. To characterize the functional role of these transcripts, we performed RNA interference mediated transient gene silencing in the epidermis of susceptible plants. Interestingly, independent silencing of TmPAL, TmCOMT, TmCCoAOMT and TmCAD led to higher penetration efficiencies of Bgt than in controls but to varying degrees. Co-silencing of TmPAL and TmCAD led to greater penetration of Bgt than when either was silenced, separately. These results suggest that monolignol biosynthesis during the formation of cell wall appositions in wheat is critically important for host defense in the response to Bgt invasion.
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1 - Department of Biology, University of Saskatchewan, SK, Canada
cell wall appositions
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM