# Transcriptional Analysis of Masson Pine
## 1 Introduction  
As humans enter an industrial society, environmental issues have become increasingly prominent. Global warming has been widely monitored by governments and the public worldwide and has risen to become one of the most important political, diplomatic, and economic issues [1]. According to the Global Carbon Project (GCP), global CO\({}_{2}\) emissions from fossil fuels and industry reached 36.8 Gt in 2017, an increase of approximately 65% from the baseline year (1990) of the Kyoto Protocol [2].  
And atmospheric CO\({}_{2}\) concentrations will rise from 380 ppm today to 550 ppm by 2050 [3]. These numbers are increasing because of the overuse of fossil fuels. Therefore, mitigating global warming caused by the increase in the CO\({}_{2}\) concentration in the atmosphere has become a serious global challenge.  
Studies have shown that elevated CO\({}_{2}\) concentrations cause changes in plant morphological structures [4], reduce stomatal conductance [5] and the leaf nitrogen metabolism rate [6] and impact other reactions. To maintain normal growth and development, plants have developed a series of physiological, biochemical and molecular regulatory mechanisms, including stomatal regulation, ion homeostasis, signal transduction, etc [7]. Tolerance to high CO\({}_{2}\) concentrations is a complex trait controlled by genes that play important roles in CO\({}_{2}\) stress responses in various plants, including heat shock proteins [8], WRKY [9; 10], and other photosynthetic-related genes [11]. These previous studies have indicated that the overexpression of these genes could increase the resistance of plants to CO\({}_{2}\) stress and that the tolerance of plants to high concentrations of CO\({}_{2}\) could be improved by transgenic and molecular marker-assisted breeding.  
Masson pine (_Pinus massoniana_) is a conifer species distributed in 17 provinces, autonomous regions and municipalities located south of the Qinling Mountains in China. It thrives in a warm and humid climate, growing in arid, barren gravel soil and sandy soil. It is a pioneer species for restoring forests in barren hills [12]. Studies have shown that the carbon sequestration capacity of Masson pine is much higher than the average carbon sequestration of forests in China [13]. The carbon sequestration of each organ of Masson pine is between 533.93 and 568.08 g\(\cdot\)kg\({}^{-1}\), which is higher than the carbon content of 32 common tree species (444.0-494.5 g\(\cdot\)kg\({}^{-1}\)) [14]. In recent years, there have been many studies on the physiological and biochemical responses to CO\({}_{2}\) stress and the screening of candidate CO\({}_{2}\)-resistance genes [15; 16; 17]; however, few studies on the CO\({}_{2}\) tolerance mechanism and transcriptome response of Masson pine have been reported. In this study, a next-generation transcriptome sequencing analysis of Masson pine under high CO\({}_{2}\) stress was evaluated using the Illumina HiSeq sequencing platform. The transcriptome results were used to identify genes that might be involved in the response to CO\({}_{2}\) and to clarify the possible molecular mechanisms involved in the adaptation to CO\({}_{2}\) stress. To verify the accuracy of the sequencing results, we selected several genes for quantitative real-time PCR (qRT-PCR) verification. The results improve our understanding of environmental acclimation mechanisms in Masson pine and serve as a molecular-level reference to inform future work on the enhancement of CO\({}_{2}\) tolerance in Masson pine.