Six-Rowed Spike3 (VRS3) Is a Histone Demethylase That Controls Lateral Spikelet Development in Barley.

The complex nature of crop genomes has long prohibited the efficient isolation of agronomically relevant genes. However, recent advances in next-generation sequencing technologies provide new ways to accelerate fine-mapping and gene isolation in crops. We used RNA sequencing of allelic () mutants with altered spikelet development for gene identification and functional analysis in barley (). Variant calling in two allelic mutants revealed that encodes a putative histone Lys demethylase with a conserved zinc finger and Jumonji C and N domain. Sanger sequencing of this candidate gene in independent allelic mutants revealed a series of mutations in conserved domains, thus confirming our candidate as the gene and suggesting that the row type in barley is determined epigenetically. Global transcriptional profiling in developing shoot apical meristems of suggested that VRS3 acts as a transcriptional activator of the row-type genes () and (; ). Comparative transcriptome analysis of the row-type mutants , (), and confirmed that all three genes act as transcriptional activators of and quantitative variation in the expression levels of in these mutants correlated with differences in the number of developed lateral spikelets. The identification of genes and pathways affecting seed number in small grain cereals will enable to further unravel the transcriptional networks controlling this important yield component.