Based on the transcriptome sequences from 45 libraries of stem tips, leaves, and xylem of Betula platyphylla (birch), three BEE genes (BpBEE1, BpBEE2, and BpBEE3), were obtained bioinformatics and expression patterns of three genes were analyses. Results showed that three BpBEE genes belonged to basic helix-loop-helix (bHLH) transcription factor superfamily, and contained a typical DNA binding domain and E-box/N-box specificity sites. These genes were highly homologous to AtBEE genes, and belonged to the 25th sub-class in the bHLH superfamily. During the growing season, the RNA level of all three BpBEE genes were high-estin leaves than in others tissues. In the vigorous growing stage, All BpBEE genes were up-regulated in leaves and buds. With the brassinosteroids (BR) treatment, BpBEE1 was up-regulated in buds and xylem (> 2 times) in the early stages (2 h and 4 h); whereas, BpBEE2 was up-regulated in the xylem and buds in the early stage (2 h). These results suggested that the three BpBEE genes could be involved in the growth process of birch, and response for BR hormone, BpBEE1 and BpBEE2 showeds early reply responses, especially.%根据已有的白桦Betula platyphylla茎尖、叶片及木质部等45个转录组信息，获得3条白桦BEE基因的全长cDNA序列，分别命名为BpBEE1, BpBEE2和BpBEE3。对3个BpBEE基因进行了生物信息学分析和实时定量聚合酶链式反应分析，结果表明：3个基因具有典型的结合DNA及特异识别序列E-box和N-box，属于bHLH类转录因子。这3个基因与拟南芥Arabidopsis thaliana中AtBEE基因亲缘关系较近，属于bHLH超家族第25亚类。在白桦生长季内， BpBEE1, BpBEE2和BpBEE3在不同组织中均有表达，叶中BpBEE基因表达量明显高于其他部位。在生长旺盛时期，茎、叶和顶芽中BpBEE基因均呈现上调表达，表明BpBEE基因可能参与到白桦的生长过程。油菜素内酯（BR）激素处理之后， BpBEE1在早期（2 h 和4 h）的芽和木质部中呈显著上调（＞2倍）； BpBEE2在早期（2 h）的木质部和芽显著上调外，其他处理时间也呈现不同程度的上调。表明3个白桦BpBEE基因参与BR激素应答，且BpBEE1和BpBEE2呈现早期应答响应。图5表2参16
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