Transcriptome analysis of exogenous biological stimulants to enhance alkaline resistance and alkali stress response of Camellia oleifera

Exogenous biological stimulants (EBS) have made some progress in alleviating non-biological stress. However, the specific mechanism of EBS on Camellia oleifera seedlings under alkaline stress (AS) remains unclear. This study aims to explore the effect of EBS on the physiological responses of C. oleifera seedlings under AS and reveal its possible mechanism of action. In the AS treatment group, the photosynthetic pigments, photosynthetic parameters and fluorescence parameters of C. oleifera seedlings decreased significantly. It is also worth noting that the MT3 group increased the soluble sugar and soluble protein contents of C. oleifera seedlings, while reducing the contents of malondialdehyde, proline and electrical conductivity. Through correlation analysis, principal component analysis and comprehensive evaluation of membership functions, it was concluded that the comprehensive score of the CK group was the highest, followed by the MT3 group, and the score of the AS treatment group was the lowest. Based on this, we conducted transcriptomic analysis on these 3 groups to further explore their differences. GO enrichment analysis was performed on DEGs (174) at the intersection of the CK-vs-AS and AS-vs-MT3 treatment groups. According to the results of the significant enrichment bubble plot, it can be known that the cross DEGs in the CK-vs-AS and AS-vs-MT3 comparison groups was significantly enriched in the two functional items of tetrapyrrole binding and heme binding. Meanwhile, KEGG pathway enrichment analysis of DEGs revealed enrichment in the sesquiterpenoids and triterpenoid biosynthesis, glutathione metabolism, isoflavone biosynthesis, phenylpropene biosynthesis, biosynthesis of secondary metabolites (BSM) pathways. Notably, the DEGs such as PRS2 , SALR and the CYP family in the BSM pathway were significantly down-regulated in the MT3 group. This study enhances our understanding of the role of EBS in AS by revealing how C. oleifera increases resistance through EBS spraying in the presence of AS. ● Camellia oleifera seedlings are relatively sensitive to alkaline stress. ● The MT3 group showed a better alleviation effect under alkaline stress. ● DEGs enriched in tetrapyrrole/heme binding and secondary metabolite biosynthesis pathways.