vrs1

Vrs1, named Six-rowed Spike 1, is a gene in barley (Hordeum vulgare) that controls the architecture of the inflorescence, specifically the row-type of the spike. Barley spikes can be two-rowed or six-rowed, referring to the fertility of lateral spikelets along the rachis. The functional Vrs1 allele promotes a two-rowed spike by suppressing the fertility of lateral spikelets; a nonfunctional allele, commonly referred to as vrs1, results in six-rowed spikes in which lateral spikelets become fertile.

Genetic and molecular basis: Vrs1 encodes a transcription factor that regulates spike development during inflorescence formation. The gene's activity forms part of a regulatory network that coordinates spikelet fertility with the developmental program of the spike.

Genomic context and importance: Vrs1 is located on chromosome 2H in barley. Variation at this locus has been a major focus of studies on barley domestication and breeding because row-type influences grain number per spike and processing quality. The two-rowed form and six-rowed form reflect natural allelic diversity at Vrs1 and related loci, and breeders exploit this variation to tailor yield and end-use characteristics.

Research and beyond: Vrs1 has been studied in conjunction with other row-type genes to map the genetic network controlling spike architecture. Cloning and functional analyses have helped illuminate how transcriptional regulation shapes inflorescence patterning in cereals.