Background Flavonoids have a wide range of biological activities in plant development, stress resistance and human health, etc. R2R3-MYBs are one of the key elements in regulation of flavonoid production, but their functional importance in Betula platyphylla remains elusive. Methods The full-length transcriptome data of 30-day-old seedlings of Betula platyphylla were used to identify BpR2R3-MYB family genes, and their gene structure, chromosome distribution and syntenic relationships were predicted by bioinformatics methods. Agrobacterium-mediated transient transformation was used to verify the function of BpR2R3-pMYB15 in flavonoid production. Results 44 BpR2R3-MYB family genes expressed in seedlings of Betula platyphylla were identified and found to be unevenly distributed in 11 chromosomes. Among them, 90.90% of the BpR2R3-MYBs had introns, and only four genes had no introns. Five gene pairs with segment duplication were found, and their Ka/Ks ratios were less than 1. Thirty orthologs between Betula platyphylla and Arabidopsis thaliana and 68 orthologs between Betula platyphylla and Populus trichocarpa were detected. Five BpR2R3-MYBs were clustered with R2R3-MYB genes related to flavonoid synthesis, and BpR2R3-pMYB15 had the highest correlation coefficients between the value of gene expression and flavonoid content. BpR2R3-pMYB15 was cloned, and its transient overexpression obtained using Agrobacterium-mediated transformation positively regulated flavonoid production. Conclusion This work enriches the collection of R2R3-MYBs related to flavonoid production in seedlings of Betula platyphylla. Graphical Abstract

Background Basic leucine zipper (bZIP) transcription factors are crucial in plant development, and response to environmental stress, etc. With the development of sequencing technology and bioinformatics analysis, the bZIP family genes has been screened and identified in many plant species, but bZIP family genes has not been systematically characterized and identified their function in Betula platyphylla. Methods B. platyphylla reference genome was used to characterize bZIP family genes. The physicochemical properties, chromosome distribution, gene structure, and syntenic relationships were analyzed by bioinformatics methods. The effect of BpbZIP26 on triterpenoid production was investigated using Agrobacterium-mediated transient transformation under N6022 treatment. Results 51 bZIP family genes were identified in B. platyphylla, and named BpbZIP1–BpbZIP51 sequentially according to their positions on chromosomes. All BpbZIP genes were unevenly distributed on 14 chromosomes, and divided into 13 subgroups according to the classification of Arabidopsis thaliana bZIP proteins. 12 duplication events were detected in the B. platyphylla genome, and 28 orthologs existed between B. platyphylla and A. thaliana, 83 orthologs existed between B. platyphylla and Glycine max, and 73 orthologs existed between B. platyphylla and Populus trichocarpa. N6022 treatment changed gene expression levels of most BpbZIPs in seedlings of B. platyphylla. Among of them, N6022 treatment significantly enhanced gene expression levels of BpbZIP26 in leaves, stems and roots of B. platyphylla. BpbZIP26 mediated triterpenoid production, and N6022 treatment further enhanced triterpenoid production in BpbZIP26 overexpression calli of B. platyphylla using Agrobacterium-mediated transient transformation. Conclusion This work highlights potential BpbZIP family genes responding to S-nitrosothiol and provides candidate genes for triterpenoid production in B. platyphylla. Graphical Abstract