Structure of Flavonoid 3′‐Hydroxylase Gene for Pubescence Color in Soybean

Abstract

The T locus of soybean [Glycine max (L.) Merr.] controls pubescence and seed coat color and it is presumed to encode a flavonoid 3′‐hydroxylase (F3′H). Dominant T and recessive t allele of the locus produce tawny and gray pubescence, respectively. Alleles at the T locus are associated with chilling tolerance. We previously cloned the entire cDNA of F3′H gene (sf3′h1) from soybean. In this report, the entire F3′H gene was characterized by isolating two genomic clones covering the entire gene. Sequence analysis revealed that F3′H gene consists of three exons and two introns distributed in a 8500‐bp DNA segment. The promoter region of the F3′H gene contains a putative G‐box, two MYB‐binding domains, and TA‐repeats. The structure and number of the TA repeats was cultivar‐dependent and highly polymorphic. A pair of simple sequence repeat (SSR) primers designated as SoyF3′H was developed to flank the TA‐repeats. The SSR band polymorphism cosegregated with genotypes at T locus in 89 F2 plants segregating for the T locus. The SSR marker may be a useful internal marker of the F3′H gene and is applicable even among cultivars with similar pubescence color. The promoter sequence information obtained in this report may be useful for investigations on the transcriptional control of F3′H gene as well as transgenic experiments to clarify the relationship between F3′H gene and chilling tolerance in soybean.