Hd1, MAJOR PHOTOPERIOD-SENSITIVITY QTL IN RICE, ENCODES A PROTEIN WITH THE STRUCTURE OF ZINC FINGER TRANSCRIPTION FACTOR

¹ National Institute of Agrobiological Resources, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan

² Bio-oriented Technology Research Advancement Institution, Oomiya, Saitama 331-8537, Japan

³ Institute of the Society for Techno-innovation of Agriculture, Forestry and Fisheries, Tsukuba, Ibaraki 305-0854, Japan

⁴ Department of Biology, Faculty of Science, Toyama University, 3190 Gofuku, Toyama 930-8555, Japan

A major quantitative trait locus, Hd1, controlling response to photoperiod in rice, was identified by map-based cloning. High-resolution mapping enabled us to define a 12-kb genomic region as a candidate for Hd1. Further analysis revealed that Hd1 is a homologue of CONSTANS in Arabidopsis and encodes a protein with the structure of zinc finger transcription factor. Comparison of genomic sequences between functional allele of Nipponbare and non-functional allele of Kasalath revealed several variations, including base substitution, a deletion, and an insertion. By RT-PCR analysis, Hd1 mRNA was detected in seedlings and adult leaves of Nipponbare, and its expression was not affected by a change in day-length. A 43-bp deletion in a putative exon of the Hd1genomic region occurred in se1 mutant HS66, and a 433-bp insertion in a putative intron occurred in se1 mutant HS110. Hd1 mRNA products in both mutants were altered. Thus, a major gene, Se1, controlling response to photoperiod, was allelic to Hd1, based on structural and expression analysis. Genetic complementation analysis is in progress.