Molecular characterization and chromosomal localization of cytochrome P450 genes involved in the biosynthesis of cyclic hydroxamic acids in hexaploid wheat

Abstract

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).

Phylogenomics of the benzoxazinoid biosynthetic pathway of Poaceae: gene duplications and origin of the Bx cluster

“…Both maize and wheat BX3 enzymes hydroxylate indoline-2-one as well as 1,4-benzoxazin-3-one [15,16], suggesting that the enzyme does not discriminate between its natural substrate and its ring- expanded analog. The use of a ring-expanded substrate (HBOA) is a feature of BX5 substrate specificity that supports the origin of Bx5 from Bx3 .…”

“…from 76 to 79% identity between maize and wheat sequences, 76 to 81% between maize and wild barley sequences) and the BX enzyme substrate specificities are very high [8,15-17]. This suggests that the neofunctionalization following duplication in the ancestral, basal poaceous species was accompanied by selection on only a few sites.…”

“…Upon wounding, an additional O -methylation is activated, leading to HDMBOA [13,14] but the gene responsible for this reaction is still unknown. The same DI(M)BOA biosynthetic pathway has also been described in wheat Triticum aestivum , in rye S. cereale and in the wild barley Hordeum lechleri , the cultivated barley probably having lost the gene cluster [15-17]. The four CYP71C genes were cloned and characterized in diploid and hexaploid wheat and in wild barley [17-19].…”

Transcriptional Profiling of Rice Treated with MoHrip1 Reveal the Function of Protein Elicitor in Enhancement of Disease Resistance and Plant Growth

“…The cytochrome P450 (CYP450) family is a superfamily of enzymes that participate in metabolism and form antibiotic compounds (Zhou et al, 1999; Nomura et al, 2002). In our data, eight genes related to CYP450 were detected.…”

Mapping resistance to the bird cherry-oat aphid and the greenbug in wheat using sequence-based genotyping

“…Those compounds have been reported to play an important role in the defense of gramineous plants when they are attacked by herbivores, causing antibiotic effects on insects including various aphid species (Frey et al 1997;Niemeyer 2009). There are five hx-related genes in wheat that are identified as TaBx1 through TaBx5 (Nomura et al 2002;Nomura et al 2003). These genes are located in chromosomes 4 and 5 of the three wheat genomes, and are involved in catalyzing the hydroxylation and ring expansion of indole-3-glycerol phosphate to synthesize DIBOA and DIMBOA (Frey et al 1997;Nomura et al 2003).…”