Transcriptome profiling of two Camellia japonica varieties with different resistance reveals heat stress response Mechanisms

Camellia is semi-shade plant, which is highly vulnerable to heat stress. In order to understand the mechanism of camellia under heat stress, two C.japonica named Xiaotaohong and Zhuapolian that have significant difference in resistance were selected as the material from four common C.japonica varieties. The selection methods were phenotype observation and physiological index detection, including REC , MDA content, SOD enzyme activity and chlorophyll content. RNAseq analysis yielded similar to 980 million reads and identified 68455 differentially expressed genes in two C.japonica varieties during heat stress against the control samples. 12565 and 16046 DEGs were differentially expressed at 16h and 32h in Xiaotaohong during heat stress, whereas in Zhuapolian, there were 40280 and 37539 DEGs differentially expressed at 16h and 32h, respectively. KEGG enrichment analysis shows that the two varieties are enriched in the two pathways of plant hormone signal transduction and circadian rhythm at the two stages, indicating that the two pathways play an important role in the heat stress response. The reasons for the difference in resistance between the two varieties are speculated to be in plant hormone signal transduction, photosynthesis, circadian rhythm and other pathways.Some member of HSP90, HSP70 and HSP20 family are associate with heat stress response. It is speculated that the transcription factor families responsible for the difference in resistance are mainly AP2/ERF, C3H, bHLH, bZIP, MYB-related etc. A small number of HSF were also induced in response to stress. In conclusion, these result revealed the change of physiological index and molecular network of two C.japonica varieties under heat stress. In the future, molecular studies of heat stress in camellia will focus on the molecules described above. This study laid the foundation for the breeding of superior heat resistant C.japonica varieties and molecular research of C.japonica.