Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Map-Based Cloning Of The Barley Six-Rowed Spike Gene Vrs1

Takao Komatsuda¹ , Mohammad Pourkheirandish¹ , Congfen He¹ , Perumal Azhaguvel¹ , Hiroyuki Kanamori² , Dragan Perovic³ , Nils Stein³ , Andreas Graner³ , Udda Lundqvist⁴ , Tatsuhito Fujimura⁵ , Makoto Matsuoka⁶ , Takashi Matsumoto¹ , Masahiro Yano¹

¹  National Institute of Agrobiological Sciences (NIAS), Tsukuba 305-8602, Japan

²  Institute of Society for Techno-Innovation of Agriculture, Forestry and Fisheries (STAFF), Tsukuba 305-0854, Japan

³  Institute of Plant Genetics and Crop Plant Research (IPK), D-06466 Gatersleben, Germany

⁴  Svalöf Weibull AB, SE-268 81 Svalöv, Sweden

⁵  Institute of Agricultural and Forest Engineering, University of Tsukuba, Tsukuba 305-8572, Japan

⁶  BioScience Center, Nagoya University, Nagoya 464-0814, Japan

Barley has three one-flowered spikelets at each rachis node. In six-rowed barley, all three spikelets are developed and fertile with filled grain. This phenotype is controlled by the single recessive gene vrs1. In two-rowed barley, the dominant allele Vrs1 drastically suppresses the development of two lateral spikelets. Using 9831 gametes, we mapped the vrs1 locus to a 0.07 centimorgan interval, which was entirely covered with 5 BACs of cv. Morex (six-rowed). Analysis of a contiguous 406 kb sequence of 4 BACs allowed to identify a predicted homeobox gene. The gene in two-rowed cultivars encoded a homeodomain-leucine zipper protein of 222 amino acids (Hvhox1). Transcription of the homeobox gene Hvhox1 was detected in apices, and it was particularly strong at double ridge to awn primordium stage (1 to 5 mm in length). We analyzed association between Hvhox1 sequence and spike phenotype using mutants including several six-rowed (hex-v) and intermedium lines (Int-d), each being allelic to the vrs1 locus. In these mutants, we detected entire deletion of the gene region, small insertion/deletion including a single nucleotide deletion causing a frame shift, and single nucleotide substitution resulting in creation of stop codon, amino acid change, or putative modification of mRNA splicing. Based on this observation, we concluded that Vrs1 encodes the homeodomain protein, Hvhox1. In 8 six-rowed cultivars, we detected frame shifts (2 haplotypes), amino acid change, and single nucleotide change in the putative 5' regulatory region. The results indicate multiple origins of six-rowed barley during 10 thousands years old history of barley cultivation.