Triterpenoids produced by the secondary metabolism of Betula platyphylla Suk. exhibit important pharmacological activities, such as tumor inhibition, anti-HIV, and defense against pathogens, but the yield of natural synthesis is low, which is insufficient to meet people's needs. In this study, we identified two OSC genes of birch, named as BpCAS and Bpβ-AS, respectively. The expression of BpCAS and Bpβ-AS were higher levels in roots and in stems, respectively, and they induced expression in response to methyl jasmonate (MeJA), gibberellin (GA3), abscisic acid (ABA), ethylene and mechanical damage. The function of the two genes in the triterpene synthesis of birch was identified by reverse genetics. The inhibition of Bpβ-AS gene positively regulates synthesis of betulinic acid. BpCAS interference can significantly promote the upregulation of lupeol synthase gene (BPW) and β-amyrin synthase gene(BPY), and conversion of 2,3-oxidosqualene to the downstream products betulinic acid and oleanolic acid. This study provided a basis for the genetic improvement of triterpenoid synthesis in birch through genetic engineering. The obtained transgenic birch and suspension cells served as material resources for birch triterpenoid applications in further.

中文翻译：

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CAS和一种新的β-香树脂醇合成酶在桦树三萜合成中的表达特征和功能（Betula platyphylla Suk.）

白桦树次生代谢产生的三萜类化合物。具有抑制肿瘤、抗HIV、防御病原体等重要药理活性，但天然合成产率低，不能满足人们的需要。在这项研究中，我们鉴定了桦木的两个 OSC 基因，分别命名为 BpCAS 和 Bpβ-AS。BpCAS 和 Bpβ-AS 分别在根和茎中的表达水平较高，它们响应茉莉酸甲酯 (MeJA)、赤霉素 (GA3)、脱落酸 (ABA)、乙烯和机械损伤诱导表达。通过反向遗传学鉴定了这两个基因在桦木三萜合成中的功能。Bpβ-AS基因的抑制正调控桦木酸的合成。BpCAS干扰可以显着促进羽扇豆醇合酶基因（BPW）和β-香树脂醇合酶基因（BPY）的上调，以及2,3-氧化角鲨烯向下游产物桦木酸和齐墩果酸的转化。本研究为通过基因工程对桦木三萜合成进行遗传改良提供了依据。获得的转基因桦木和悬浮细胞可作为桦木三萜类化合物进一步应用的物质资源。