LkAP2L2, an AP2/ERF transcription factor gene of Larix kaempferi, with pleiotropic roles in plant branch and seed development

Larix kaempferi is an economically and ecologically valuable afforestation and timber species. However, functional genes participating in its growth and development remain largely unknown because of its long growth cycle and highly complex genetic background. In this study, LkAP2L2, an AP2/ERF transcription factor gene, was identified and the characteristics and functions of LkAP2L2 were further explored. The cDNA of LkAP2L2, with a length of 2124 bp, encodes a transcription factor comprising 707 amino acid residues. LkAP2L2 was further introduced into Arabidopsis genome using the Agrobacterium tumefaciens transformation method. The shoot branching phenotype of LkAP2L2-overexpressing Arabidopsis was enhanced. The number of their branches was almost twice as high as that of the vector control plants. In contrast to those on bushier branches, the size and number of rosette leaves were decreased by LkAP2L2 overexpression. In particular, the length of the fifth rosette leaves was shorter by approximately 17% in 35S::LkAP2L2 plants, and the number of rosette leaves was approximately 70% of that of the vector control. In addition, the length of silique was decreased by a half compared with the vector control plants, and no more than 4 seeds per silique were detected in the transgenic plants. The length of siliques and the number of seeds are decreased by LkAP2L2 through its influence on flower development. Therefore, LkAP2L2 of L. kaempferi plays a crucial role in branch, flower, silique and seed development, and this gene may be manipulated to obtain the bushy phenotype of plants.