Leaf Transcriptome and Weight Gene Co-expression Network Analysis Uncovers Genes Associated with Photosynthetic Efficiency in Camellia oleifera.

Camellia oleifera Abel. (C. oleifera) as an important economic tree species in China has drawn growing attention because of its highly commercial, medic, cosmetic, and ornamental value. To deepen our understanding about the photosynthetic characters during the whole developmental stage as well as the molecular basis of photosynthesis, a comparative analysis of the leaf transcriptome of two C. oleifera cultivars, 'Guoyou No.13' (GY13) and 'Xianglin No.82' (XL82), with different photosynthetic characteristics from May to September has been conducted. In this study, a group of genes related to photosynthesis, hormone regulation, circadian clock and transcription factor, involved in the photosynthetic advantage. Photosynthetic parameters from May to September of these two cultivars provided evidence supporting photosynthetic advantage of GY13 compared to XL82. In addition, expression levels of 12 differentially expressed genes (DEGs) were validated using real-time PCR (RT-PCR). To screen gene clusters and hub genes that might directly regulated the photosynthetic differences between cultivars, a Weight Gene Co-expression Network Analysis (WGCNA) was conducted. Three co-expression network (module) and top ten connected genes (hub genes) were identified that might play crucial role in the regulatory network of photosynthesis. The results not only showed multiple functional genes that might involve in the differences of photosynthetic characteristics between cultivars, but also provide some evidences for the heat tolerance might be an important character which helps GY13 kept higher photosynthetic parameters than XL82 during the developmental stage. In summary, our transcriptomic approach together with RT-PCR tests allowed us to expand our understanding of the characters of C. oleifera cultivars with different photosynthetic efficiency during the developmental stage and to further exploring new candidate genes involve in high photosynthetic efficiency in molecular-assisted breeding program of C. oleifera.