| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1995: ¥1,300,000 (Direct Cost: ¥1,300,000)
|
|---|
| Research Abstract |
As an approach to the understanding of the molecular mechanism of the action of cytokinins, an attempt was made to determine the structure and properties of the CR20 gene, which is rapidly repressed after application of this hormone to etiolated cotyledons of cucumber. Analysis of cDNA and genomic clones of CR20 revealed that this gene consisted of three exons At least three types of transcript were generated by alternative splicing of the second intron. However, none of these transcripts included a long open reading frame. Results of the TESTCODE analysis, which distinguishes protein-coding DNA from noncoding DNA,predicted that CR20 RNA would be a noncoding sequence. A cDNA AtCR20-1, which was isolated from a cDNA library of Arabidopsis thaliana with the CR20 cDNA as a probe, was also predicted to be a noncoding sequence by the TESTCODE.A region of 180 nt was well conserved in CR20 and AtCR20-1 RNAs, and seems to form stable stems. These suggest that the transcripts of CR20 and AtCR20-1 may be noncoding functional RNAs. In order to study the function of CR20, CR20A cDNA which contains the second intron and CR20-C cDNA which does not contain the intron were fused to a CaMV 35S promoter, and introduced into tobacco plants. One of the CR-20-A transformants showed chlorosis along midribs and loss of the activity of the apical meristem. Another one had lighter green leaves than normal plants. However, CR20-C transformants showed no different features compared with normal plants. Chlorosis induced by transformation with CR20-A would be significant, as the CR20 gene was repressed during greening which is known to be stimulated by cytokinins. Correlation between these changes and the expression of the CR20 gene is now being examined.
|
