Functional Analysis Of Transcriptional Factor SlZF6 In Tomato

Zinc finger is one type of the most abundant and extensively studied transcriptional factors, and it functions both in plant development and biotic/abiotic stress at different stages. One set of salt responsive transcriptional factors were identified in our former microarray analysis of salt stressed tomato, and their corresponding over-expression vectors were constructed and introduced into tomato. Among them, one transcriptional factor gene, SlZF6, which is 465 bp in length and encodes 154 amino acids, belongs to C2H2 type of zinc finger based on sequence alignment result. The GenBank accession number of SlZF6 is DY523809. In present study, we focused on investigating overexpression of SIZF6 in tomato, and the major results are as follows:1. Tissue expression profile analysis using semi quantitative RT-PCR indicated that SlZF6 was constitutively expressed in all tested tissues, and relatively higher expression was detected in root.2. Over-expression vector of SlZF6 was introduced into the genome of tomato cultivar Ailsa Craig (A57) through Agrobacterium mediated transformation, and 22 positive transformants were obtained after PCR identification. Southern blot analysis showed more than 78% of the transformants were positive, plants with single copy of T-DNA insertion accounted for 53.8%.3. Over expression of SlZF6 was confirmed in transgenic plants using quantitative RT-PCR, the expression of SIZF6 was increased by 19.87,4.66 and 56.85 folds in three single-copy transgenic lines, respectively.4. Genetic segregation analysis was carried out on offspring of the transgenic plants. In accordance with the southern blot result, the three single-copy transgenic lines showed a 3:1 segregation pattern in Chi-square test.5. Salt tolerance was evaluated using detached leaf discs from T1 trangenic plants, the Chlorophyll content of non-transformed leaf discs decreased more than that of transgenic ones.6. Salt and drought tolerance were characterized in T2 generation, and transcript of the transgene, seedling damage rate, proline and MDA contents were analyzed under the stresses. Proline content was increased to 4.0,16.2,3.9 and 9.6 folds, respectively, in non-transformed control plants and the three transgenic lines. The corresponding changes of proline in the control plants and transgenic lines after drought stress were 7.7,20.2,6.2, and 13.7 folds. Integrated results suggested that over-expression of SlZF6 enhanced the salt and drought tolerance of tomato.7. Phenotypic changes such as dwarf and compact leaf architecture were observed in SlZF6 overexpressing plants. The pleiotropic phenotype was inheritable and the degree of the phenotypic change depended on the expression level of transgene. These results indicated SlZF6 affect plant development in various aspects.