The nitrate-responsive protein MdBT2 regulates anthocyanin biosynthesis by interacting with the MdMYB1 transcription factor

First author: Xiao-Fei Wang; Affiliations: Shandong Agricultural University (山东农业大学): Shandong, China

Corresponding author: Yu-Jin Hao (郝玉金)

In addition to scavenging (清除) reactive oxygen species (活性氧簇), anthocyanins (花青素) are pigments that give organs their color. In apple (Malus domestica), R2R3-MYB transcription factor MdMYB1 is a master regulator of anthocyanin biosynthesis and fruit coloration. In this study, we found that MdMYB1 was degraded via an ubiquitin-dependent pathway in response to nitrate (硝酸盐), an inhibitor of anthocyanin synthesis. Using a yeast two-hybrid (Y2H) approach, we found that the BTB-TAZ protein encoded by the nitrate-responsive gene MdBT2interacts with MdMYB1. Pull-down and co-immunoprecipitation assays supported this conclusion. In vivo and in vitro experiments revealed that MdBT2 promoted the ubiquitination and degradation of MdMYB1 through a cullin protein MdCUL3-independent pathway. Expression analysis demonstrated that MdBT2 and MdMYB1 were inversely regulated by nitrate and other environmental signals. Furthermore, we used transgenic approaches in apple and Arabidopsis thalianato characterize the function of MdBT2in regulating anthocyanin biosynthesis in response to nitrate. Our findings provide insight into a mechanism involving the MdBT2-MdMYB1 pathway that regulates anthocyanin accumulation in apple and possibly in other plant species.

除了清除活性氧簇的作用外，花青素还是赋予植物器官颜色的色素。在苹果中，R2R3-MYB转录因子MdMYB1是花青素生物合成和果实着色的主要调控子。本研究揭示了MdMYB1在响应花青素生物合成抑制剂硝酸盐时，被依赖于泛素的通路所降解。利用酵母双杂的方法，作者发现由硝酸盐响应基因MdBT2所编码的BTB-TAZ蛋白与MdMYB1互作。Pull-down试验和共免疫沉淀试验再次证明了这一点。体内和体外试验均揭示了MdBT2会通过不依赖于MdCUL3的途径促进MdMYB1的泛素化和降解。表达试验揭示了MdBT2和MdMYB1受到硝酸盐和其它环境信号相反的调控。此外，作者还对苹果和拟南芥进行了转基因验证，再一次证实了MdBT2基因在响应硝酸盐的情况下发挥调控花青素生物合成的功能。本文的发现为MdBT2-MdMYB1通路调控花青素在苹果中积累的分子机制提供了新的视野。

通讯：郝玉金 (http://yyxy.sdau.edu.cn/2012/0528/c1457a15086/page.htm)

个人简介：1994年，山东农业大学，学士；1997年，山东农业大学，硕士；2000年，华中农业大学，博士；先后在北京大学、日本果树研究所（筑波）和美国加州大学河滨分校从事博士后研究。

研究方向：苹果果实品质形成；苹果砧木抗性研究。

doi: https://doi.org/10.1104/pp.18.00244

Journal: Plant Physiology

First Published date: 25 May, 2018

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