Analysis of the involvement of hydroxyanthranilate hydroxycinnamoyltransferase and caffeoyl-CoA 3-O-methyltransferase in phytoalexin biosynthesis in oat.
Two oat genes encoding hydroxycinnamoyl-CoA:hydroxyanthranilate N-hydroxycinnamoyltransferase (HHT) and S-adenosyl-L-methionine:trans-caffeoyl-CoA 3-O-methyltransferase (CCoAOMT), both of which are possibly involved in the biosynthesis of oat avenanthramide phytoalexins, were cloned and their expression profiles in response to biological stress were studied. Four distinct cDNAs of oat HHT (AsHHT1-4) were isolated with the degenerative polymerase chain reaction method. The enzymatic activity of AsHHT1 expressed in E. coli was found using hydroxyanthranilate and hydroxycinnamoyl-CoAs as cosubstrates. Cloned oat CCoAOMT (AsCCoAOMT) encoded a polypeptide of 130 amino acid residues with 77.7 to 80.8% identities to the CCoAOMT sequences from other plant species. The accumulation of AsHHT1 and AsCCoAOMT transcripts increased concomitantly with phytoalexin accumulation by the treatment of victorin, a specific elicitor in oat lines carrying the Pc-2/Vb gene. Pharmacological approaches indicated the involvement of Ca2+, NO, and protein kinases in the signaling pathways of AsHHT1 and AsCCoAOMT mRNA induction. When oat leaves were inoculated with Puccinia coronata, the mRNA expression of AsHHT1 and AsCCOAOMT increased in both incompatible and compatible interactions but more rapidly in incompatible interaction. Interestingly, however, significant phytoalexin accumulation was observed only in incompatible interaction during the experimental period, suggesting that phytoalexin accumulation may be inhibited in one or more posttranscriptional processes in the compatible interaction.
Yang
Qian
Q
Laboratory of Plant Pathology, Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan.
Trinh
Hoat Xuan
HX
Imai
Satoshi
S
Ishihara
Atsushi
A
Zhang
Liqun
L
Nakayashiki
Hitoshi
H
Tosa
Yukio
Y
Mayama
Shigeyuki
S
D000217:Acyltransferases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D018554:Avena / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005658:Fungi / Q000254:growth & development*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010936:Plant Extracts / Q000096:biosynthesis*; D018515:Plant Leaves / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012717:Sesquiterpenes; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013729:Terpenes; D000094162:Phytoalexins
D018076:DNA, Complementary; D010936:Plant Extracts; D010940:Plant Proteins; D012717:Sesquiterpenes; D013729:Terpenes; D008780:Methyltransferases; C059825:caffeoyl-CoA O-methyltransferase; C019608:caffeate O-methyltransferase; D000217:Acyltransferases; C407879:hydroxycinnamoyl-CoA hydroxyanthranilate N-hydroxycinnamoyltransferase; D000094162:Phytoalexins