Ectopic Expression of Poplar Reduces Cell Size and Regulates Flower Organ Development in .

The D-type cyclin (CYCD) gene, as the rate-limiting enzyme in the G1 phase of cell cycle, plays a vital role in the process of plant growth and development. Early studies on plant cyclin mostly focused on herbs, such as . The sustainable growth ability of woody plants is a unique characteristic in the study of plant cyclin. Here, the promoter of was cloned from poplar by PCR and genetically transformed into tobacco. A strong GUS activity was observed in the areas with vigorous cell division, such as stem tips, lateral buds, and young leaves. The fusion expression vector was transformed into tobacco, and the green fluorescence signal was observed in the nucleus. Compared with the control plant, the transgenic tobacco showed significant changes in the flower organs, such as enlargement of sepals, petals, and fruits. Furthermore, the stems of transgenic plants were slightly curved at each stem node, the leaves were curled on the adaxial side, and the fruits were seriously aborted after artificial pollination. Microscopic observation showed that the epidermal cells of petals, leaves, and seed coats of transgenic plants became smaller. The transcriptional levels of endogenous genes, such as , , , and , were upregulated by . Therefore, gene played an important role in the regulation of flower organ and stem development, providing new understanding for the functional characterization of gene and new resources for improving the ornamental value of horticultural plants.