AGAMOUS-like 6 and MYB DOMAIN PROTEIN 80 regulate the development of female and male cones in Pinus densiflora S. et Z.

To shorten the long breeding period of forest trees, it is necessary to explore biological factors and key genes involved in reproduction. We compared the transcriptomes of female and male cones and then identified major biological processes and hub genes associated with the development of female and male cones in Pinus densiflora. The reproductive and vegetative tissues of P. densiflora were sampled from various developmental stages and a reference transcriptome was generated. Functional annotation and Gene Ontology enrichment analysis of differentially expressed genes were performed as well as gene co-expression network analysis for identifying the hub genes involved in the cone development. Lignin biosynthesis and cell wall loosening were activated in the early and late female cones, respectively. Metabolism of pollen wall components was predominant in the early male cones compared with the later stage. In addition, phytohormone-related genes were highly expressed in the early female cones in contrast to the early male cones. Finally, we found that AGAMOUS-like 6 and MYB DOMAIN PROTEIN 80 were hub genes of the female and male cone development, respectively. This study suggests that various biological factors contribute to reproductive developmental processes. Furthermore, these data will provide the new insight into biotechnology and breeding methods for improving cone and seed production of P. densiflora.