Six-rowed barley originated from a mutation in a homeodomain-leucine zipper I-class homeobox gene

Takao Komatsuda, Mohammad Pourkheirandish, Congfen He, Perumal Azhaguvel, Kiroyuki Kanamori, Dragan Perovic, Nils Stein, Andreas Graner, Thomas Wicker, Akemi Tagiri, Udda Lundqvist, Tatsuhito Fujimura, Makoto Matsuoka, Takashi Matsumoto, Masahiro Yano

Research output: Contribution to journalArticle

377 Citations (Scopus)


Increased seed production has been a common goal during the domestication of cereal crops, and early cultivators of barley (Hordeum vulgare ssp. vulgare) selected a phenotype with a six-rowed spike that stabty produced three times the usual grain number. This improved yield established barley as a founder crop for the Near Eastern Neolithic civilization. The barley spike has one central and two lateral spikelets at each rachis node. The wild-type progenitor (H. vulgare ssp. spontaneum) has a two-rowed phenotype, with additional, strictly rudimentary, lateral rows; this natural adaptation is advantageous for seed dispersal after shattering. Until recently, the origin of the six-rowed phenotype remained unknown. In the present study, we isolated vrs1 (six-rowed spike 1), the gene responsible for the six-rowed spike in barley, by means of positional cloning. The wild-type Vrs1 allele (for two-rowed barley) encodes a transcription factor that includes a homeodomain with a closely linked leucine zipper motif. Expression of Vrs1 was strictly localized in the lateral-spikelet primordia of immature spikes, suggesting that the VRSt protein suppresses development of the lateral rows. Loss of function of Vrs1 resulted in complete conversion of the rudimentary lateral spikelets in two-rowed barley into fully developed fertile spikelets in the six-rowed phenotype. Phylogenetic analysis demonstrated that the six-rowed phenotype originated repeatedly, at different times and in different regions, through independent mutations of Vrs1.

Original languageEnglish
Pages (from-to)1424-1429
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number4
Publication statusPublished - 23 Jan 2007
Externally publishedYes

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