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Vernalization requirement and vernalization response

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  1. Introduction.
  2. Vernalization requirement evolved independently in temperate cereals.
  3. Vernalization response.
  4. Arabidopsis vernalization respons.
  5. Vernalization response in species other than Arabidopsis.
  6. Connecting cold to vernalization.
  7. Evolution of vernalization.
  8. Short-day vernalization.
  9. Conclusion.

The major loci controlling vernalization requirement in the diploid wheat Triticum monococcum are VRN1 and VRN2 (in cereals the VERNALIZATION, VRN, designation applies to genes conferring a vernalization requirement and differs from Arabidopsis genes of the same name that are involved in vernalization response). These two genes have strong epistatic interactions and are likely to be part of the same regulatory pathway. VRN1 is located on wheat chromosome 5. Genes controlling vernalization requirement in barley and rye map to syntenic regions, as judged by their co-segregation with common markers, indicating that related genes control vernalization requirement in these different cereals.

[...] Short-day Vernalization While vernalization is the acquisition or acceleration of the ability to flower following a chilling treatment, a similar effect has been observed by exposing some plants, like wheat and barley, to SDs. Flowering of wheat and barley is promoted in response to LDs; spring varieties and vernalized winter varieties generally accelerate flowering in response to LDs. However, the response of unvernalized winter varieties today length is less consistent. Some winter varieties of wheat and barley display earlier flowering if growth in SDs precedes transfer to LD conditions. [...]

[...] As vernalization requirement in barley maps to positions syntenic with VRN1 and VRN2 known as Sgh2 and Sgh1, respectively or VRN-H1 and VRN-H2, this indicates that vernalization requirement involves related genes in wheat and barley and that differences between winter and spring habit involved mutation of similar genes. A gene homologous to VRN2 (ZCCT1) is present in a collinear region of winter barley and can be identified by DNA hybridization using ZCCT1 as a probe. Vernalization Response Progress towards the characterization of the molecular basis of vernalization response has so far depended on induced mutations and the analysis of natural variation in this trait. [...]

[...] In contrast, vernalization requirement has evolved independently in Arabidopsis and cereals. This difference in the conservation of different aspects of flowering-time control might be explained by the number of potential alternative targets that could confer a vernalization requirement. As flowering-time control features a network of multiple pathways feeding into overlapping floral pathway integrators, which in turn control floral meristem-identity genes, there are many alternative mechanisms by which floral repression could evolve. If these were sensitive to cold, they could establish independent mechanisms of conferring a vernalization requirement. [...]

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