Norwich, United Kingdom
15 November 2001

Scientists at the John Innes Centre (JIC) Norwich, have identified and isolated a gene that gives plants a 'memory'. The gene, called VRN22, is described for the first time tomorrow (16th November), in the international scientific journal Cell. VRN2(*) - short for vernalisation2 - enables plants to 'remember' throughout their life, that they have been exposed to a period of cold temperature early in their growth. In many plants vernalisation (the acceleration of flowering by a cold period of 3-8 weeks at 4o- 8oC) is important as it ensures flowering is delayed through winter until the favourable conditions of spring and summer. The isolation of this gene will not only enable scientists to better understand the biology of flowering and how to alter vernalisation requirements in crop plants, but also adds to studies of the evolution of these chemical 'memories' in different organisms.

"We have known for some time that many plants need cold treatment (vernalisation) to accelerate
flowering", said Professor Caroline Dean (an Associate Research Director at JIC and head of the team that identified how VRN2 works). "We have now isolated a gene that enables the plant to remember that it has had a cold treatment once warm growing conditions return".

The common weed, Arabidopsis thaliana (Mouse-ear or Thale Cress) would flower 3-4 weeks after seed germination if it were not for the activity of a gene (called FLC) which inhibits the flowering process and delays the production of flowers for up to 3 months.

Scientists measured the effect of cold on the FLC gene and discovered that a period of low temperatures (3-8 weeks at 4o- 8oC), reduced the activity of the gene. In this 'low activity' state,
the gene's ability to inhibit flowering is reduced and so the time taken for the plant to flower is reduced. Plants that would take 3 months to flower without a cold treatment, will flower in a few weeks if they are vernalised (kept in the cold for a month) and then returned to warm growth conditions.

"It was at this point that we discovered the importance of VRN2 in providing the plant with a memory", said Professor Dean. "We found some plants where the VRN2 gene is not working (because of a mutation). In these plants FLC activity is reduced in the cold, but on return to warm conditions its activity increases again. This inhibits flowering and these plants did not flower for several months, even after vernalisation. When we investigated VRN2 we discovered that it makes a product that alters the structure of the DNA in the FLC gene. This 'locks' FLC in the 'low activity' position that is induced by cold, even when the plant is returned to warm conditions. In these plants flowering is no longer inhibited by FLC and they flower in a few weeks. VRN2 itself is not affected by cold treatments, but it enables the plant to remember the cold treatment even after it has been returned to warm conditions and so is essential to the vernalisation process".

By taking advantage of the relative simplicity of the genetics of Arabidopsis the scientists were able to isolate the normal and mutant forms of VRN2 gene and compare their structures with those of other plant and animal genes. Interestingly, VRN2 is closely related to a gene in fruit flies, which has a similar role in providing a chemical memory that 'locks' specific genes into a particular level of activity over prolonged periods of time and/or cycles of cell division and growth.

This work was supported by BBSRC4 grant 208/MOL4649 and the BBSRC competitive strategic
grant to JIC.

The Intellectual Property Rights associated with this discovery are assigned to Plant Biosciences
Ltd.

(*) The VRN2 gene has been mapped to long arm of Arabidopsis chromosome IV. The coding region of VRN2 appears to be 1718bp and is predicted to encode a 445 amino acid protein of approximately 51KDa. The mutated gene, contains a point mutation (guanine to adenine base change) at position 1195, which converts TGG to TGA and thus inserts a premature stop codon in the sequence. VRN2 has significant homology with two other Arabidopsis genes and the "polycomb-group" genes of the fruit fly (Drosophila melanogaster). In all cases these related genes appear to be involved in on-going suppression of transcription and provide epigenetic control of gene expression over prolonged time and developmental periods.

The John Innes Centre (JIC), Norwich, UK is an independent, world-leading research centre in plant and microbial sciences. The JIC has over 850 staff and students. JIC carries out high quality fundamental, strategic and applied research to understand how plants and microbes work at the molecular, cellular and genetic levels. The JIC also trains scientists and students, collaborates with many other research laboratories and communicates its science to end-users and the general public. The JIC is grant-aided by the Biotechnology and Biological Sciences Research Council.


The BBSRC (Biotechnology and Biological Sciences Research Council) is a non-departmental public body, established by Royal Charter to promote research and training in the non-medical life sciences so as to contribute to the economic competitiveness of the UK and the quality of life. It is principally funded through the Science Budget by the Department of Trade and Industry via the Office of Science and Technology.

Plant Biosciences Limited (PBL) is a for-profit technology transfer and intellectual property management company specializing in plant and microbial science and is the intellectual property management company of the John Innes Centre and the Sainsbury Laboratory. All enquiries regarding the commercial exploitation of this IPR should be addressed to PBL who may be contacted on 01603 456500.

Reference URL : http://www.jic.bbsrc.ac.uk/staff/caroline-dean/vernalization.htm