茉莉素调控红梨花青苷和黄酮/异黄酮竞争合成的分子机制研究

Flavonoids are important bioactive compounds in plants which include anthocyanins, flavones/ isoflavones, flavonols, and proanthocyanins. Our previous studies found that jasmonate could induce both anthocyanins and flavones/isoflavones accumulation, which may cause the competition for precursors. Furthermore, ethylene played crucial roles in this process. Jasmonate mainly induced anthocyanin biosynthesis in the absence of ethylene, while mainly induced flavones/isoflavones biosynthesis in the presence of ethylene. In this project, candidate transcription factors (TF) which respond to jasmonate and co-express with anthocyanin or flavones/isoflavones biosynthetic key genes will be selected according to transcriptome analysis. We will further verify the interaction between JAZ proteins and these candidate TFs using Yeast two-hybrid assay, BiFC assay, Pull-down assay and Co-IP assay. Furthermore, the biological function of these candidate TFs will be verified by performing virus induced gene silence (VIGS) or overexpressing in ‘Red Zaosu’ pear fruits, as well as overexpressing or using RNAi to silence in pear callus. The phenotype of coloration and the expression of flavonoids biosynthesis related genes will be analyzed. Moreover, the competition of synthesis between anthocyanin and flavones/isoflavones will also be validated. We will also verify the interaction between EIN3/EIL TFs in ethylene signaling pathway and JAZ proteins to illuminate that in the presence of ethylene, jasmonate inhibits anthocyanin accumulation and induces flavones/isoflavones accumulation. Our study can enrich the molecular theory about the regulation of flavonoid biosynthesis and provide the basis for the breeding and practice application to improve the pear fruit coloration.

类黄酮是一类非常重要的次生代谢物，包括花青苷、黄酮/异黄酮、黄酮醇、原花青素等不同分支化合物。前期研究发现茉莉素能同时调控红梨果皮的花青苷、黄酮/异黄酮合成，且两者的合成存在竞争，该竞争关系受乙烯调控：不存在乙烯时，花青苷合成占主导地位；存在乙烯时，黄酮/异黄酮合成占主导地位。本项目在此基础上，通过转录组分析筛选转录因子，验证其与茉莉素信号通路JAZ蛋白的互作，利用反向遗传学手段，将候选转录因子在梨愈伤组织和‘红早酥’梨果皮上过表达或沉默，观察表型并分析相关基因表达，明确茉莉素调控花青苷和黄酮/异黄酮合成的分子机制及两者的竞争关系。进一步验证乙烯信号通路EIN3/EIL蛋白和JAZ蛋白的互作，明确存在乙烯时，茉莉素通过EIN3/EIL抑制花青苷合成，促进黄酮/异黄酮合成的分子机制。本项目的研究结果不仅可以丰富植物类黄酮调控的分子生物学理论，还能为定向改良梨果皮色泽的分子育种提供理论依据。

类黄酮是一类非常重要的次生代谢产物，包括花青苷、黄酮/异黄酮、黄酮醇、原花青素等不同分支化合物。前期研究发现茉莉素能同时调控红梨果皮的花青苷、黄酮/异黄酮合成，且两者的合成存在竞争关系，该竞争关系受乙烯调控：不存在乙烯时，茉莉素诱导花青苷合成占主导地位；存在乙烯时，茉莉素诱导黄酮/异黄酮合成占主导地位。本项目在前期研究基础上，通过‘红早酥’梨和‘茄梨’愈伤组织的相关激素处理和转录组分析进一步明确了茉莉素和乙烯对花青苷和黄酮/异黄酮合成的影响。通过分子生物学和遗传学验证阐明了茉莉素通过PpMYB17调控红梨果皮类黄酮合成的分子机制；明确了茉莉素通过PpMYC2和PpbHLH13维持红梨花青苷合成稳态的分子机制；解析了乙烯通过PpERF105-PpMYB140抑制红梨花青苷合成的分子机制；明确了乙烯介导PpERF9-PpTPL1共抑制复合体通过组蛋白去乙酰化作用抑制红梨花青苷合成的分子机制。本项目的研究结果不仅从转录调控、蛋白互作和表观调控等多个角度丰富了植物类黄酮调控的分子生物学理论，还为定向改良梨果皮色泽的分子育种提供了多个候选基因和充实的理论依据。