MYB12 promotes flavonol biosynthesis in plants by targeting several early biosynthesis genes (EBGs) of this pathway. The transcriptions of these EBGs are also induced by sucrose signal. However, whether MYB12 is activated by sucrose signal and what the other roles MYB12 has in regulating plant metabolism are poorly understood. In this study, two NtMYB12 genes were cloned from Nicotiana tabacum. Both NtMYB12a and NtMYB12b are involved in regulating flavonoids biosynthesis in tobacco. NtMYB12a is further shown to inhibit the accumulation of fatty acid (FA) in tobacco leaves and seeds. Post‐translational activation and chromatin immunoprecipitation assays demonstrate that NtMYB12a directly promotes the transcriptions of NtLOX6, NtLOX5, NtSFAR4 and NtGDSL2, which encode lipoxygenase (LOX) or SFAR enzymes catalyzing the degradation of FA. NtLOX6 and NtLOX5 are shown to prevent the accumulation of FA in the mature seeds and significantly reduced the percentage of polyunsaturated fatty acids (PUFAs) in tobacco. Sucrose stimulates the transcription of NtMYB12a, and loss function of NtMYB12a partially suppresses the decrease of FA content in tobacco seedlings caused by sucrose treatment. The regulation of sucrose on the expression of NtLOX6 and NtGDSL2 genes is mediated by NtMYB12a, whereas those of NtLOX5 and NtSFAR4 genes are independent of sucrose.

中文翻译：

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NtMYB12a在蔗糖下游起作用，通过靶向烟草中的脂氧合酶和SFAR基因来抑制脂肪酸积累

MYB12通过靶向该途径的多个早期生物合成基因（EBG）来促进植物中黄酮醇的生物合成。这些EBG的转录也由蔗糖信号诱导。然而，对于MYB12是否被蔗糖信号激活以及MYB12在调节植物代谢中的其他作用知之甚少。在这项研究中，从烟草（Nicotiana tabacum）克隆了两个NtMYB12基因。NtMYB12a和NtMYB12b均参与调节烟草中类黄酮的生物合成。NtMYB12a进一步显示抑制烟叶和种子中脂肪酸（FA）的积累。翻译后激活和染色质免疫沉淀实验表明NtMYB12a直接促进NtLOX6，NtLOX5的转录，NtSFAR4和NtGDSL2，它们编码脂氧化酶（LOX）或SFAR酶催化FA的降解。NtLOX6和NtLOX5可以防止FA在成熟种子中积累，并显着降低烟草中多不饱和脂肪酸（PUFA）的百分比。蔗糖刺激NtMYB12a的转录，NtMYB12a的丧失功能部分抑制了蔗糖处理引起的烟草幼苗中FA含量的降低。蔗糖对NtLOX6和NtGDSL2基因表达的调节是由NtMYB12a介导的，而NtLOX5和NtSFAR4基因的蔗糖则独立于蔗糖。