Full-Length Transcriptome Analysis of the Secondary-Growth-Related Genes of Pinus massoniana Lamb. with Different Diameter Growth Rates

Abstract

Secondary growth is the main source of wood accumulation and has an extremely complex regulation process. Pinus massoniana Lamb. is one of the main timber tree species in China and it is of great significance in the study of the secondary growth process. The full-length transcriptome from the stems of P. massoniana with different diameter growth rates was obtained by PacBio and 15,448 full-length transcripts were identified. A comparative transcriptome analysis revealed that 408 genes were differentially expressed between the fast-growing wood (FGW) and slow-growing wood (SGW). The important regulatory genes involved in the secondary growth of P. massoniana (cell division, cell wall biosynthesis, lignification, and programmed cell death), such as ARL8, POD, EXPA8, Ecm33, and RhoA, were identified by a GO and KEGG annotation analysis. The differential expression of the key genes in the lignin synthesis pathway were obtained, such as PAL, 4CL, CCR, HCT, and PER. In addition, the abscisic acid receptor gene PYL and the ethylene biosynthesis key gene EFE were screened for their involvement in the regulation of the secondary growth of P. massoniana. It is speculated that these genes coordinate the processes of secondary growth to promote the rapid growth of FGW. This study preliminarily explored the differential mechanism of the growth rate of P. massoniana and provided a reference for obtaining new P. massoniana germplasm with a high quality and excellent yield.