Genome-wide identification of AP2/ERF gene family in Coptis Chinensis Franch reveals its role in tissue-specific accumulation of benzylisoquinoline alkaloids.

Background: The Plant-specific AP2/ERF gene family encodes proteins involved in various biological and physiological processes. Although the genome of Coptis chinensis Franch, a plant producing benzylisoquinoline alkaloids (BIAs), has been sequenced at the chromosome level, studies on the AP2/ERF gene family in C. chinensis are lacking. Thus, a genome-wide identification of AP2/ERF gene family in C. chinensis was conducted to explore its role in BIAs biosynthesis.

Results: A total of 96 CcAP2/ERF genes were identified and categorized into five subfamilies, including 43 ERFs, 32 DREBs, 17 AP2s, 3 RAVs, and 1 Soloist, based on their structural domains. These CcAP2/ERF genes were unevenly distributed across nine chromosomes. Analysis of gene duplication events identified 17 CcAP2/ERF gene pairs in the genome, with 7 involved in tandem duplication events and 10 involved in segmental duplicate events, indicating that both types of duplications contributed to the expansion of the AP2/ERF gene family. The Ka/Ks ratio analysis suggested that the CcAP2/ERF gene family underwent strong purifying selection. Two phytohormones, methyl jasmonate and abscisic acid, were identified as potential key inducers of BIAs biosynthesis due to the cis-acting element prediction. Analysis of the spatial transcriptomic data revealed that 28 differentially expressed AP2/ERF genes had the highest or relatively higher expression levels in the rhizome, 17 of which positively correlated with the tissue-specific accumulation of BIAs. Further real-time PCR verification and protein-protein interaction analysis indicated that DREB1B might be one of the central regulators in a highly complex BIAs biosynthesis network.

Conclusion: These findings provide significant insight into the function of AP2/ERF genes in C. chinensis, particularly in the regulatory network of BIAs biosynthesis in C. chinensis. This study also identifies candidate genes for metabolic engineering to increase BIAs content in C. chinensis.