Molecular characterization of the allelic variation at the VRN-H2 vernalization locus in barley

Abstract

VRN-2 is a dominant repressor of flowering that plays a central role in the vernalization pathway of wheat. This gene is a zinc-finger/CCT domain transcription factor (ZCCT-1) down-regulated by vernalization. In barley, there are three related and linked ZCCT genes designated VRN-H1a, b, and c. A deletion of these three genes was observed in six putative spring induced mutants from winter barley variety ‘Chikurin Ibaraki I’. However, analysis of additional molecular markers demonstrated that these deletions were originated by outcrossing with a spring barley variety carrying the natural ZCCT deletion. Hybridization of Southern blots from 84 barley varieties with a wheat ZCCT1 probe showed three or more fragments in 23 winter varieties but none in 60 out of the 61 vrn-H2 spring varieties. The vrn-H2-spring barley variety ‘Fan’ showed only the ZCCT-Hb gene, suggesting that this gene is not sufficient to determine winter growth habit in barley. We also show in this study, that the effect of VRN-H2 on flowering time completely disappears in the presence of the dominant Vrn-H1 allele in a Morex × Hordeum spontaneum segregating population. A different result was described before for the epistatic interactions between the orthologous genes in diploid wheat. We discuss the possible causes of these differences.