Jasmonates (JAs) are among the main phytohormones, regulating plant growth and development, stress responses, and secondary metabolism. As the major regulator of the JA signaling pathway, MYC2 also plays an important role in plant secondary metabolite synthesis and accumulation. In this study, we performed a comparative transcriptome analysis of seedlings subjected to methyl jasmonate (MeJA) at different treatment times. A total of 31,193 differentially expressed genes (DEGs) were identified by RNA sequencing. Among them, 732 differentially expressed transcription factors (TFs) comprising 51 TF families were characterized. The most abundant TF family was WRKY proteins (80), followed by AP2/ERF-EFR (67), MYB (59), bHLH (52), and NAC protein (49) families. Subsequently, by calculating the Pearson's correlation coefficient (PCC) between the expression level of TF DEGs and the lycorine contents, 41 potential TF genes (|PCC| >0.8) involved in lycorine accumulation were identified, including 36 positive regulators and 5 negative regulators. Moreover, a MeJA-inducible gene (namely ) was cloned on the basis of transcriptome sequencing. Bioinformatic analyses revealed that LaMYC2 proteins contain the bHLH-MYC_N domain and bHLH-AtAIB_like motif. LaMYC2 protein is localized in the cell nucleus, and can partly rescue the mutant in . LaMYC2 protein could interact with most LaJAZs (especially LaJAZ3 and LaJAZ4) identified previously. Transient overexpression of increased lycorine contents in petals, which might be associated with the activation of the transcript levels of () and () genes. By isolating the 887-bp-length promoter fragment upstream of the start codon (ATG) of , we found several different types of E-box motifs (CANNTG) in the promoter of . Further study demonstrated that LaMYC2 was indeed able to bind the E-box (CACATG) present in the promoter, verifying that the pathway genes involved in lycorine biosynthesis could be regulated by LaMYC2, and that LaMYC2 has positive roles in the regulation of lycorine biosynthesis. These findings demonstrate that LaMYC2 is a positive regulator of lycorine biosynthesis and may facilitate further functional research of the gene, especially its potential regulatory roles in Amaryllidaceae alkaloid accumulation in .

中文翻译：

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对 MeJA 响应的转录因子基因的鉴定和 LaMYC2 转录因子的表征对石蒜中石蒜碱生物合成的正调节

茉莉酸 (JAs) 是主要的植物激素之一，调节植物生长发育、应激反应和次生代谢。 MYC2作为JA信号通路的主要调节因子，在植物次生代谢产物的合成和积累中也发挥着重要作用。在这项研究中，我们对不同处理时间的茉莉酸甲酯（MeJA）幼苗进行了比较转录组分析。通过RNA测序共鉴定出31,193个差异表达基因（DEG）。其中，包括 51 个 TF 家族的 732 个差异表达转录因子 (TF) 被表征。最丰富的 TF 家族是 WRKY 蛋白 (80)，其次是 AP2/ERF-EFR (67)、MYB (59)、bHLH (52) 和 NAC 蛋白 (49) 家族。随后，通过计算TF DEGs表达水平与石蒜碱含量之间的Pearson相关系数（PCC），鉴定出41个与石蒜碱积累相关的潜在TF基因（|PCC|>0.8），其中包括36个正调节基因和5个负调节基因。此外，基于转录组测序，克隆了MeJA诱导基因（即 ）。生物信息学分析表明，LaMYC2 蛋白含有 bHLH-MYC_N 结构域和 bHLH-AtAIB_like 基序。 LaMYC2蛋白定位于细胞核，可以部分拯救突变体。 LaMYC2 蛋白可以与之前发现的大多数 LaJAZ（尤其是 LaJAZ3 和 LaJAZ4）相互作用。花瓣中石蒜碱含量增加的瞬时过度表达，这可能与 () 和 () 基因转录水平的激活有关。通过分离 的起始密码子（ATG）上游的 887 bp 长度的启动子片段，我们在 的启动子中发现了几种不同类型的 E-box 基序（CANNTG）。进一步的研究表明，LaMYC2确实能够结合启动子中存在的E-box（CACATG），验证了LaMYC2可以调控参与石蒜碱生物合成的通路基因，并且LaMYC2在石蒜碱生物合成的调控中具有积极的作用。这些发现表明LaMYC2是石蒜碱生物合成的正调节因子，可能有助于该基因的进一步功能研究，特别是其在石蒜科生物碱积累中的潜在调节作用。