| The MADS box family of genes encodes for transcription factors and are found in a diverse range of eukaryotic organisms including yeast, plants, insects, amphibians and mammals. In plants, the major function of the MADS box genes is in controlling the flower development process.; Two MADS box genes, PtAP1 and PtAGL4 have been cloned from male and female flowers of Populus tremuloides . The genes are highly homologous to the Arabidopsis APETALA1 and AGL4. Northern blot analysis revealed the floral tissue specificity of these genes. Temporal expression pattern suggests that PtaP1 is expressed during the early stages and PtAGL4 during the later stages of male and female aspen flower development. Neither of these genes are expressed in vegetative tissue. Given the high degree of homology between the MADS box genes of different species, the observed divergence in sequence and expression patterns of the male and female aspen genes might suggest a sex specific expression of MADS box genes in dioecious aspen. Over and under expression of the PtMAGL4 gene in transgenic tobacco was performed to determine the function of this gene. Transgenic tobacco over-expressing the PtMAGL4 resulted in transgenic tobacco flowering four weeks earlier than the wild type. Conversely, under-expression of PtMAGL4 delayed flowering in transgenic tobacco by 6 weeks and in some transgenic lines showed no sips of flowering even after 10 weeks. Over-expression of PtMAGL4 also resulted in the conversion of dormant vegetative meristems into floral meristems, thereby altering the branching pattern and increasing flowering. Therefore, it appears that the PtAGL4 gene is involved in controlling flowering time and is also involved in the conversion of vegetative meristem to floral meristem. |
