title: Complete loss of photoperiodic response in the rice mutant line X61 is caused by deficiency of phytochrome chromophore biosynthesis gene.
abstract: In rice (Oryza sativa), a short-day plant, photoperiod is the most favorable external signal for floral induction because of the constant seasonal change throughout the years. Compared with Arabidopsis, however, a large part of the regulation mechanism of the photoperiodic response in rice still remains unclear due mainly to the lack of induced mutant genes. An induced mutant line X61 flowers 35 days earlier than its original variety Gimbozu under a natural photoperiod in Kyoto (35°01'N). We attempted to identify the mutant gene conferring early heading to X61. Experimental results showed that the early heading of X61 was conferred by a complete loss of photoperiodic response due to a novel single recessive mutant gene se13. This locus interacts with two crucial photoperiod sensitivity loci, Se1 and E1. Wild type alleles at these two loci do not function in coexistence with se13 in a homozygous state, suggesting that Se13 is an upstream locus of the Se1 and E1 loci. Linkage analysis showed that Se13 is located in a 110 kb region between the two markers, INDEL3735_1 and INDEL3735_3 on chromosome 1. A database search suggested that the Se13 gene is identical to AK101395 (=OsHY2), which encodes phytochromobilin synthase, a key enzyme in phytochrome chromophore biosynthesis. Subsequent sequence analysis revealed that X61 harbors a 1 bp insertion in exon 1 of OsHY2, which induces a frame-shift mutation producing a premature stop codon. It is therefore considered that the complete loss of photoperiodic response of X61 is caused by a loss of function of the Se13 (OsHY2) gene involved in phytochrome chromophore biosynthesis.
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyou, Kyoto, 606-8502, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Saito
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Okumoto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yoshitake
authors.forename: Hiromo
authors.initials: H
authors.lastname: Inoue
authors.forename: Qingbo
authors.initials: Q
authors.lastname: Yuan
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Teraishi
authors.forename: Takuji
authors.initials: T
authors.lastname: Tsukiyama
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Nishida
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Tanisaka
mesh_terms: D001483:Base Sequence; D002874:Chromosome Mapping; D020090:Chromosome Segregation / Q000235:genetics; D032461:Chromosomes, Plant / Q000235:genetics; D003433:Crosses, Genetic; D017343:Genes, Plant / Q000235:genetics*; D005819:Genetic Markers; D005838:Genotype; D007564:Japan; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D012275:Oryza / Q000235:genetics*; D017440:Photoperiod; D010834:Phytochrome / Q000096:biosynthesis* / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D040641:Quantitative Trait Loci / Q000235:genetics; D012621:Seasons; D017422:Sequence Analysis, DNA
chemical_list: D005819:Genetic Markers; D010834:Phytochrome