| PttKN1(Populus tremula×tremuloides KN0TTED1) gene, which was isolated from the vascular cambium of a hybrid aspen (P. tremula×P. tremuloides), is a gene highly homologous to the KNOX genes of Class I ( KNOX I) in plant. The KNOX I genes encode a transcription factor, which have been conformed to take an important part in regulation of plant growth and development. It has been demonstrated that the members of KNOX I family not only determine the cell fate of shoot apical meristem, but also control the initiation and development of the lateral organs. When the KNOX I gene overexpressed in transgenic plants, many abnormal phenotypes could be found in leaf, flower, plants and vascular bundle. To get insights into the function of the KNOX I gene existing in wood plant, and exploring the possibility of improving the properties of the gardening plant, we introduced this PttKN1 into the genomes of flowering plant, Petunia hybrida and two different ecology types of Arabidopsis ( Nossen and Landsberg erecta) using the leaf disc or flower dipping methods mediated by Agrobacterium tumefaciens, and more systemically analyzed the function of this gene. We gain several main results below.1. Total 21 Pttkn1 transgenic plants were obtained using the leaf disc method mediated by Agrobacterium tumefaciens in Petunia hybrida. RT-PCR analysis confirmed 6 groups of the Pttkn1 transgenic plants to be positive; According to phenotype, they can be classified into 6 groups, 4 of which have important enjoying values due to their beautiful flowers. By the flower dipping method mediated by Agrobacterium tumefaciens, total 64 Pttkn1 transgenic plants were obtained in Arabidopsis, including 29 Nossen type, which can be divided into 2 phenotypes, and 35 Landsberg erecta type, which can be divided into 3 phenotypes, based on their morphology.2. RT-PCR analysis indicated that PttKN1 gene had really been introduced into the genomes of the plant species above, which expressed in the plants resistant to kanamycin, but did not in wild-type plants.3. When the PttKN1 gene was overexpressed in Petunia hybrida, the transgenic plants exhibited the following abnormal features: 1) lobed, wavy or petioleless leaves and leaves with ectopic meristems; 2) shortened internodes, stunted plant with acervate appearance; 3) lost apical dominance and scrubby plant; 4) shortened and dissected corolla, distorted petals and ones with knots; 5) number-increased flower organs and fused flowers; 6) the corolla with out or with shortened midvein. 7) the vascular cambium of stem and leaf was thickened, and some ectopic meristems were formed on leaves.4. When the PttKN1 gene was overexpressed in Arabidopsis (Nossen), serrate leaves were changed into pinnately dissect leaves, petiole was widened, and the venation pattern of leaves became abnormal compared with wild type, abnormal cell morphology were found in stem.5. When the PttKN1 gene was overexpressed in Arabidopsis (Landsberg erecta), the leaves changed into asymmetric ones with a crinkly lamina and the numbers of inflorescences and flowers were increased. The adaxial-abaxial polarity of leaves was disturbed.Taken together, the following conclusions were suggested:1. The leaves of wile-type petunia are entire and elliptical, while the leaves of the transgenic petunia are palmately dissect; the leaves of the wild-type Arabidopsis are serrate and elliptical, and the leaves of the transgenic Arabidopsis are pinnately dissect. So the different developmental pattern determined the different leave phenotype.2. Because the overexpression of PttKN1 gene made the number of inflorescences and flowers increasing in Arabidopsis (Landsberg erecta), and the number of inflorescences and flowers are one of the important agronomic traits for crop production, the interaction of KNOX genes and ERECTA gene could make a significant contribution of future improvement of crops.3. Because PttKN1 gene, as a gene encoding for a transcription factor, is likely to play a role in the maintenance of the indeterminate properties of meristem cells, and ERECTA gene, encoding for a receptor protein kinase, possibly functions in cell-cell communication, so the above data suggest that interaction between PttKN1 and ERECTA genes is required for fine-tuning the proliferation and growth of cells in the same tissue during Arabadopsis development.4. Because PttKN1 gene was isolated from the vascular cambium of aspen stem (wood plant), it is likely that PttKN1 gene impacted the phenotype of both leaf and flower by controlling the development of vascular tissue.
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