Nomura T, Ishihara A, Imaishi H, Endo T R, Ohkawa H, Iwamura H
Japan Society for the Promotion of Science, Japan.
Mol Genet Genomics. 2002 Apr;267(2):210-7. doi: 10.1007/s00438-002-0653-x. Epub 2002 Mar 2.
The cyclic hydroxamic acids, 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), are defensive secondary metabolites found in gramineous plants including wheat, maize and rye. cDNAs for five cytochromes P450 (P450s) involved in DIBOA biosynthesis (CYP71C6, CYP71C7v2, CYP71C8v2, CYP71C9v1 and CYP71C9v2) were isolated from seedlings of hexaploid wheat [( Triticum aestivum L. cv. Chinese Spring (2n=6x=42, genomes AABBDD)] by RT-PCR and screening of a cDNA library. CYP71C9v1 and CYP71C9v2 are 97% identical to each other in amino acid and nucleotide sequences. The cloned P450 species showed 76-79% identity at the amino acid level to the corresponding maize P450 species CYP71C1-C4, which are also required for DIBOA biosynthesis. The wheat P450 cDNAs were heterologously expressed in the yeast ( Saccharomyces cerevisiae) strain AH22. Microsome fractions from yeast cells expressing these P450 species catalyzed the same reactions as their maize orthologs. The chromosomes carrying the cyp71C6- C9v1 orthologs were identified by Southern hybridization using aneuploid lines of Chinese Spring wheat. The cyp71C9v1 orthologs were located on the chromosomes of wheat homoeologous group-4. The orthologs of the other P450 genes, cyp71C7v2, cyp71C6 and cyp71C8v2, were located on group-5 chromosomes. The same P450 genes were also present in the three ancestral diploid species of hexaploid wheat, T. monococcum (AA), Aegilops speltoides [BB (approximately SS)] and Ae. squarrosa (DD).
环状异羟肟酸，即2,4 - 二羟基 - 1,4 - 苯并恶嗪 - 3 - 酮（DIBOA）和2,4 - 二羟基 - 7 - 甲氧基 - 1,4 - 苯并恶嗪 - 3 - 酮（DIMBOA），是在包括小麦、玉米和黑麦在内的禾本科植物中发现的防御性次生代谢产物。通过逆转录聚合酶链反应（RT-PCR）和筛选cDNA文库，从六倍体小麦[(普通小麦（Triticum aestivum L. cv. Chinese Spring，2n = 6x = 42，基因组AABBDD）]的幼苗中分离出参与DIBOA生物合成的5种细胞色素P450（P450s）的cDNA（CYP71C6、CYP71C7v2、CYP71C8v2、CYP71C9v1和CYP71C9v2）。CYP71C9v1和CYP71C9v2在氨基酸和核苷酸序列上彼此的同源性为97%。克隆的P / 450物种在氨基酸水平上与玉米相应的P450物种CYP71C1 - C4的同源性为76 - 79%，而这些玉米P450物种也是DIBOA生物合成所必需的。小麦P450 cDNA在酵母（Saccharomyces cerevisiae）菌株AH22中进行了异源表达。表达这些P450物种的酵母细胞的微粒体部分催化与它们的玉米直系同源物相同的反应。使用中国春小麦的非整倍体系通过Southern杂交鉴定携带cyp71C6 - C9v1直系同源物的染色体。cyp71C9v1直系同源物位于小麦同源群4的染色体上。其他P450基因cyp71C7v2、cyp71C6和cyp71C8v2的直系同源物位于5组染色体上。相同的P450基因也存在于六倍体小麦的三个祖先二倍体物种，即一粒小麦（AA）、斯卑尔脱山羊草[BB（近似SS）]和节节麦（DD）中。
