Transcriptome Characteristics and Six Alternative Expressed Genes Positively Correlated with the Phase Transition of Annual Cambial Activities in Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook)

Zhanjun Wang,Pengkai Wang,Yanjuan Zhang,Weidong Liu,Zhanshou Luo,Jinhui Chen,Jisen Shi,Renhua Zheng,Nicholas S Foulkes

doi:10.1371/journal.pone.0071562

Abstract

BackgroundThe molecular mechanisms that govern cambial activity in angiosperms are well established, but little is known about these molecular mechanisms in gymnosperms. Chinese fir (Cunninghamia lanceolata (Lamb.) Hook), a diploid (2n = 2x = 22) gymnosperm, is one of the most important industrial and commercial timber species in China. Here, we performed transcriptome sequencing to identify the repertoire of genes expressed in cambium tissue of Chinese fir.Methodology/Principal FindingsBased on previous studies, the four stage-specific cambial tissues of Chinese fir were defined using transmission electron microscopy (TEM). In total, 20 million sequencing reads (3.6 Gb) were obtained using Illumina sequencing from Chinese fir cambium tissue collected at active growth stage, with a mean length of 131 bp and a N50 of 90 bp. SOAPdenovo software was used to assemble 62,895 unigenes. These unigenes were further functionally annotated by comparing their sequences to public protein databases. Expression analysis revealed that the altered expression of six homologous genes (ClWOX1, ClWOX4, ClCLV1-like, ClCLV-like, ClCLE12, and ClPIN1-like) correlated positively with changes in cambial activities; moreover, these six genes might be directly involved in cambial function in Chinese fir. Further, the full-length cDNAs and DNAs for ClWOX1 and ClWOX4 were cloned and analyzed.ConclusionsIn this study, a large number of tissue/stage-specific unigene sequences were generated from the active growth stage of Chinese fir cambium. Transcriptome sequencing of Chinese fir not only provides extensive genetic resources for understanding the molecular mechanisms underlying cambial activities in Chinese fir, but also is expected to be an important foundation for future genetic studies of Chinese fir. This study indicates that ClWOX1 and ClWOX4 could be possible reverse genetic target genes for revealing the molecular mechanisms of cambial activities in Chinese fir.

Highlights

Wood formation involves the cambium cell activities of division and differentiation, including cell expansion, cell wall thickening, lignification, and programmed cell death [1,2,3]
In this study, a large number of tissue/stage-specific unigene sequences were generated from the active growth stage of Chinese fir cambium
This study indicates that ClWOX1 and ClWOX4 could be possible reverse genetic target genes for revealing the molecular mechanisms of cambial activities in Chinese fir

Summary

Introduction

Wood formation involves the cambium cell activities of division and differentiation, including cell expansion, cell wall thickening, lignification, and programmed cell death [1,2,3]. With the completion of genome sequences for model plants such as Arabidopsis [15] and Populus [16], many molecular mechanisms and genes involved in cambial activity, such as TDIF/CLE41/ CLE44-TDR/PXY-WOX4 [17,18,19,20,21,22], Class III HD-Zip/KANADI [23,24,25,26], have been identified in angiosperms [27]. Little is known about the molecular mechanisms and genes in gymnosperms. The molecular mechanisms of cambial activity in gymnosperms can be revealed using NGS in the active growth stage of the cambium zone. The molecular mechanisms that govern cambial activity in angiosperms are well established, but little is known about these molecular mechanisms in gymnosperms. We performed transcriptome sequencing to identify the repertoire of genes expressed in cambium tissue of Chinese fir

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Conclusion