title: Six-rowed spike4 (Vrs4) controls spikelet determinacy and row-type in barley.
abstract: Inflorescence architecture of barley (Hordeum vulgare L.) is common among the Triticeae species, which bear one to three single-flowered spikelets at each rachis internode. Triple spikelet meristem is one of the unique features of barley spikes, in which three spikelets (one central and two lateral spikelets) are produced at each rachis internode. Fertility of the lateral spikelets at triple spikelet meristem gives row-type identity to barley spikes. Six-rowed spikes show fertile lateral spikelets and produce increased grain yield per spike, compared with two-rowed spikes with sterile lateral spikelets. Thus, far, two loci governing the row-type phenotype were isolated in barley that include Six-rowed spike1 (Vrs1) and Intermedium-C. In the present study, we isolated Six-rowed spike4 (Vrs4), a barley ortholog of the maize (Zea mays L.) inflorescence architecture gene RAMOSA2 (RA2). Eighteen coding mutations in barley RA2 (HvRA2) were specifically associated with lateral spikelet fertility and loss of spikelet determinacy. Expression analyses through mRNA in situ hybridization and microarray showed that Vrs4 (HvRA2) controls the row-type pathway through Vrs1 (HvHox1), a negative regulator of lateral spikelet fertility in barley. Moreover, Vrs4 may also regulate transcripts of barley SISTER OF RAMOSA3 (HvSRA), a putative trehalose-6-phosphate phosphatase involved in trehalose-6-phosphate homeostasis implicated to control spikelet determinacy. Our expression data illustrated that, although RA2 is conserved among different grass species, its down-stream target genes appear to be modified in barley and possibly other species of tribe Triticeae.
authors.affiliation: Department of Genebank, Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben D06466, Germany.
authors.forename: Ravi
authors.initials: R
authors.lastname: Koppolu
authors.forename: Nadia
authors.initials: N
authors.lastname: Anwar
authors.forename: Shun
authors.initials: S
authors.lastname: Sakuma
authors.forename: Akemi
authors.initials: A
authors.lastname: Tagiri
authors.forename: Udda
authors.initials: U
authors.lastname: Lundqvist
authors.forename: Mohammad
authors.initials: M
authors.lastname: Pourkheirandish
authors.forename: Twan
authors.initials: T
authors.lastname: Rutten
authors.forename: Christiane
authors.initials: C
authors.lastname: Seiler
authors.forename: Axel
authors.initials: A
authors.lastname: Himmelbach
authors.forename: Ruvini
authors.initials: R
authors.lastname: Ariyadasa
authors.forename: Helmy Mohamad
authors.initials: HM
authors.lastname: Youssef
authors.forename: Nils
authors.initials: N
authors.lastname: Stein
authors.forename: Nese
authors.initials: N
authors.lastname: Sreenivasulu
authors.forename: Takao
authors.initials: T
authors.lastname: Komatsuda
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schnurbusch
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D005298:Fertility / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006239:Haplotypes; D001467:Hordeum / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D056626:Inflorescence / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D010940:Plant Proteins
keywords: EGG APPARATUS1; cytokinin; grain number; yield potential