Regions associated with repression of the barley (Hordeum vulgare) VERNALIZATION1 gene are not required for cold induction

Abstract

Activity of the VERNALIZATION1 (VRN1) gene is required for flowering in temperate cereals such as wheat and barley. In varieties that require prolonged exposure to cold to flower (vernalization), VRN1 is expressed at low levels and is induced by vernalization to trigger flowering. In other varieties, deletions or insertions in the first intron of the VRN1 gene are associated with increased VRN1 expression in the absence of cold treatment, reducing or eliminating the requirement for vernalization. To characterize natural variation in VRN1, the first intron of the barley (Hordeum vulgare) VRN1 gene (HvVRN1) was assayed for deletions or insertions in a collection of 1,000 barleys from diverse geographical regions. Ten alleles of HvVRN1 containing deletions or insertions in the first intron were identified, including three alleles that have not been described previously. Different HvVRN1 alleles were associated with differing levels of HvVRN1 expression in non-vernalized plants and with different flowering behaviour. Using overlapping deletions, we delineated regions in the HvVRN1 first intron that are associated with low levels of HvVRN1 expression in non-vernalized plants. Deletion of these intronic regions does not prevent induction of HvVRN1 by cold or the maintenance of increased HvVRN1 expression following cold treatment. We suggest that regions within the first intron of HvVRN1 are required to maintain low levels of HvVRN1 expression prior to winter but act independently of the regulatory mechanisms that mediate induction of HvVRN1 by cold during winter.

Identification of the VERNALIZATION 4 gene reveals the origin of spring growth habit in ancient wheats from South Asia

“…TaGRP2 binding to the VRN1 pre-mRNA is required for the inhibition of VRN1 expression (21), so the disruption of this interaction can explain the earlier expression of VRN-D4. This mechanism is also consistent with the spring growth habit associated with large deletions in the first intron of VRN1, including the RIP-3 region (20,68).…”

Vrn-D4 is a vernalization gene located on the centromeric region of chromosome 5D in hexaploid wheat

“…Deletions and mutations involving both ZCCT1 and ZCCT2 genes are frequent in diploid wheat and barley and are associated with recessive alleles for spring growth habit Hemming et al 2009;Yan et al 2004a). Among the tetraploid wheat species, the Vrn-B2 gene is generally functional whereas the Vrn-A2 gene is not (Distelfeld et al 2009b).…”

Direct links between the vernalization response and other key traits of cereal crops

“…Sequences in the first intron might also regulate processing of the VRN1 transcript 15 . Several active alleles of VRN1 with deletions or insertions in the first intron have been identified in barley [16][17][18][19] . These reduce the vernalization requirement to different extents and have been used to breed varieties that flower without vernalization, which are grown where winters are warm or where crops are sown in spring 19,20 .…”

“…Several active alleles of VRN1 with deletions or insertions in the first intron have been identified in barley [16][17][18][19] . These reduce the vernalization requirement to different extents and have been used to breed varieties that flower without vernalization, which are grown where winters are warm or where crops are sown in spring 19,20 . In addition to flowering without vernalization, varieties of wheat or barley that carry active alleles of VRN1 typically have reduced freezing tolerance 21,22 .…”