The term vernalization is derived from the Latin word vernus meaning ‘of the spring'. Vernalization was defined as ‘the acquisition or acceleration of the ability to flower by a chilling treatment'. The promotion of flowering by vernalization is the result of subjecting an imbibed seed or young plant to a long period of cold (typically weeks). Floral initiation does not occur in the cold treatment but only after returning the plant to a higher temperature and in many cases a specific photoperiod. Therefore, cold temperatures do not cause plants to initiate floral primordia, but create the capacity for subsequent flowering. Vernalization can be facultative or obligate. Winter annuals have a facultative vernalization requirement, as cold accelerates, but this is not required for flowering. Biennials, cannot flower without cold treatment and therefore have an obligate requirement for vernalization. Summer annuals flower rapidly without a vernalization treatment.
[...] FLC appears to be the most important of these with respect to vernalization requirement and response. It is important to mention that although the regulation of FLC is the most important feature of Arabidopsis vernalization requirement, it is not the only one; flc null mutants exhibit a vernalization response. Interestingly, some of the MAF genes are also regulated by vernalization in a manner similar to FLC, while others are regulated in the reciprocal pattern i.e. upregulated by vernalization. The second group of factors determining FLCmRNAexpression levels is the autonomous pathway which was originally described as a genetic pathway that regulates flowering time independently of photoperiod. [...]
[...] Considerable variation exists in flowering time and vernalization requirement, and this is also likely to relate to adaptation to particular environments. These distinctions are clearly pertinent to agriculture and winter/summer annualism is an important trait in breeding programmes as it influences the geographical range in which crop plants can be grown. Vernalization-requiring crops are typically sown in the autumn and are known as winter types. In contrast, non-vernalization-requiring agritypes are typically sown in the spring and known as spring types. [...]
[...] This has long indicated an epigenetic basis to this aspect of the vernalization response. Addressing the mechanisms of vernalization using Arabidopsis as a model Our considerate of the molecular processes that underpin much of plant biology has been transformed in the last 10 years through molecular genetics approaches and the use of Arabidopsis as a model. This is mainly true of recent progress in dissecting the mechanisms of flowering-time control. Arabidopsis is native to temperate latitudes and its flowering is promoted in response to LDs and vernalization. [...]
[...] The importance of FLC in determining the vernalization requirement of Arabidopsis is a consequence of its strong repressive effect on flowering time, and its ability to be downregulated by exposure to low temperatures. The comparison of winter- and summer-annual (or rapid cycling) Arabidopsis accessions has revealed that the rapid- cycling habit of Arabidopsis evolved from a winter-annual habit most commonly through loss of FRI function or, more rarely, as a result of weak alleles of flc. Several different FRI and FLC alleles have been described. [...]
[...] The close connection of flower development to seasonal progression makes flowering-time control an important aspect of how plants adapt to their environment and logically, therefore, is an important part of crop plant breeding programmes. Consistent with this, ecotypes and agritypes of the same species show different flowering responses and one of the most striking distinctions relates to winter/summer annualism. The widespread uptake of Arabidopsis thaliana as the laboratory-based model of modern plant biology is partly due to its rapid life cycle. In the wild, most Arabidopsis ecotypes are winter annuals that exhibit extremely delayed flowering unless exposed to a vernalization treatment. [...]
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