Biosynthesis and emission of insect-induced methyl salicylate and methyl benzoate from rice.
Two benzenoid esters, methyl salicylate (MeSA) and methyl benzoate (MeBA), were detected from insect-damaged rice plants. By correlating metabolite production with gene expression analysis, five candidate genes encoding putative carboxyl methyltransferases were identified. Enzymatic assays with Escherichia coli-expressed recombinant proteins demonstrated that only one of the five candidates, OsBSMT1, has salicylic acid (SA) methyltransferase (SAMT) and benzoic acid (BA) methyltransferase (BAMT) activities for producing MeSA and MeBA, respectively. Whereas OsBSMT1 is phylogenetically relatively distant from dicot SAMTs, the three-dimensional structure of OsBSMT1, which was determined using homology-based structural modeling, is highly similar to those of characterized SAMTs. Analyses of OsBSMT1 expression in wild-type rice plants under various stress conditions indicate that the jasmonic acid (JA) signaling pathway plays a critical role in regulating the production and emission of MeSA in rice. Further analysis using transgenic rice plants overexpressing NH1, a key component of the SA signaling pathway in rice, suggests that the SA signaling pathway also plays an important role in governing OsBSMT1 expression and emission of its products, probably through a crosstalk with the JA signaling pathway. The role of the volatile products of OsBSMT1, MeSA and MeBA, in rice defense against insect herbivory is discussed.
Zhao
Nan
N
Department of Plant Sciences, 252 Ellington Plant Sciences Building, University of Tennessee, 2431 Joe Johnson Drive, Knoxville, TN 37996, USA.
Guan
Ju
J
Ferrer
Jean-Luc
JL
Engle
Nancy
N
Chern
Mawsheng
M
Ronald
Pamela
P
Tschaplinski
Timothy J
TJ
Chen
Feng
F
D000818:Animals; D001565:Benzoates / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism; D004926:Escherichia coli; D015870:Gene Expression; D017343:Genes, Plant; D007113:Immunity, Innate / Q000235:genetics; D007313:Insecta; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism; D015394:Molecular Structure; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D054883:Oxylipins / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics*; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012459:Salicylates / Q000378:metabolism*; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics
D001565:Benzoates; D003517:Cyclopentanes; D054883:Oxylipins; D010937:Plant Growth Regulators; D011994:Recombinant Proteins; D012459:Salicylates; C044605:methyl benzoate; C011006:jasmonic acid; D008780:Methyltransferases; C033069:methyl salicylate; D020156:Salicylic Acid