文摘
The effects of a maize knotted1 (kn1) gene under the control of the cauliflower mosaic virus 35S promoter on genetic transformation efficiencies of six citrus genotypes were tested. The kn1 gene construct was used to transform ‘Pineapple’, ‘Hamlin’, ‘Sucarri’ and ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck], ‘Carrizo’ Citrange [Citrus sinensis (L.) Osbeck × Poncirus trifoliate (L.) Raf.] and Eureka lemon [Citrus. limon (L.) Burm.f.] via Agrobacterium tumefaciens-mediated infection. Our results demonstrate that expression of the kn1 gene enhances transformation efficiencies from 3 to 15 fold compared to a control vector, 3–11 fold relative to the highest transformation efficiencies reported for these citrus genotypes. Stable incorporations of T-DNA into the citrus genome have been confirmed with both histochemical staining of GUS activity and molecular analyses. The majority of kn1 over-expressing citrus plants grow and develop normally at young seedling stages, similar to those of the wild type plants. With all six genotypes of citrus tested including Eureka lemon, a cultivar difficult to be transformed, our results demonstrate that the kn1 gene may provide an effective molecular tool to enhance genetic transformation efficiencies of various citrus varieties. High transformation efficiency of citrus is of great importance for large scale characterization of gene functions and also cultivar development via transgenic and genome editing technologies.