Abstract：
CONCLUSIONS: DzMYB2 functions as an MYB activator, while DzMYB3 acts as an MYB repressor. They bind to promoters, interact with DzbHLH1, and influence phenolic contents, revealing their roles in phenylpropanoid regulation in durian pulps. Durian fruit has a high nutritional value attributed to its enriched bioactive compounds, including phenolics, carotenoids, and vitamins. While various transcription factors (TFs) regulate phenylpropanoid biosynthesis, MYB (v-myb avian myeloblastosis viral oncogene homolog) TFs have emerged as pivotal players in regulating key genes within this pathway. This study aimed to identify additional candidate MYB TFs from the transcriptome database of the Monthong cultivar at five developmental/postharvest ripening stages. Candidate transcriptional activators were discerned among MYBs upregulated during the ripe stage based on the positive correlation observed between flavonoid biosynthetic genes and flavonoid contents in ripe durian pulps. Conversely, MYBs downregulated during the ripe stage were considered candidate repressors. This study focused on a candidate MYB activator (DzMYB2) and a candidate MYB repressor (DzMYB3) for functional characterization. LC-MS/MS analysis using Nicotiana benthamiana leaves transiently expressing DzMYB2 revealed increased phenolic compound contents compared with those in leaves expressing green fluorescence protein controls, while those transiently expressing DzMYB3 showed decreased phenolic compound contents. Furthermore, it was demonstrated that DzMYB2 controls phenylpropanoid biosynthesis in durian by regulating the promoters of various biosynthetic genes, including phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR). Meanwhile, DzMYB3 regulates the promoters of PAL, 4-coumaroyl-CoA ligase (4CL), CHS, and CHI, resulting in the activation and repression of gene expression. Moreover, it was discovered that DzMYB2 and DzMYB3 could bind to another TF, DzbHLH1, in the regulation of flavonoid biosynthesis. These findings enhance our understanding of the pivotal role of MYB proteins in regulating the phenylpropanoid pathway in durian pulps.
摘要：
结论：DzMYB2起MYB激活剂的作用，而DzMYB3充当MYB阻遏物。他们绑定到发起人，与DzbHLH1相互作用，并影响酚类含量，揭示了它们在榴莲果肉中苯丙素调节中的作用。榴莲果实具有很高的营养价值归因于其丰富的生物活性化合物，包括酚类物质,类胡萝卜素，和维生素。虽然各种转录因子（TFs）调节苯丙素生物合成，MYB（v-myb禽成髓细胞病病毒癌基因同源物）TFs已成为调节该途径内关键基因的关键参与者。这项研究旨在从Monthong品种的转录组数据库中确定五个发育/采后成熟阶段的其他候选MYBTF。根据在成熟榴莲果浆中观察到的类黄酮生物合成基因与类黄酮含量之间的正相关，在成熟阶段上调的MYB中可以识别出候选转录激活剂。相反，在成熟阶段下调的MYB被认为是候选阻遏物。这项研究集中于候选MYB激活剂（DzMYB2）和候选MYB阻遏物（DzMYB3）进行功能表征。使用瞬时表达DzMYB2的Nicotianabenthamiana叶片进行LC-MS/MS分析显示，与表达绿色荧光蛋白对照的叶片相比，酚类化合物含量增加，而瞬时表达DzMYB3的人显示酚类化合物含量降低。此外，研究表明，DzMYB2通过调节各种生物合成基因的启动子来控制榴莲中的苯丙素生物合成，包括苯丙氨酸解氨酶（PAL），查耳酮合成酶（CHS），查尔酮异构酶（CHI），和二氢黄酮醇还原酶（DFR）。同时,DzMYB3调节PAL的启动子，4-香豆酰辅酶A连接酶(4CL),CHS,CHI,导致基因表达的激活和抑制。此外，发现DzMYB2和DzMYB3可以与另一个TF结合，DzbHLH1，在类黄酮生物合成的调控中。这些发现增强了我们对MYB蛋白在榴莲果肉中调节类苯丙素途径中的关键作用的理解。
