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): Taian, China

Corresponding author: Yu-Jin Hao(郝玉金)

In addition to scavenging reactive oxygen species, anthocyanins 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 MdBT2 interacts 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 MdBT2 in 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.

花青素除了具有扫除活性氧物质的功能之外，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。本文的研究发现MdMYB1由响应于硝酸盐的泛素依赖通路所降解，而硝酸盐是花青素生物合成的抑制因子。通过酵母双杂的方法，作者发现由响应硝酸盐基因MdBT2编码的BTB-TAZ蛋白与MdMYB1互作。Pull-down和免疫共沉淀试验均在此支持了这个结论。体内和体外的试验揭示了MdBT2通过cullin蛋白MdCUL3自主途径促进MdMYB1的泛素化和降解。表达试验显示MdBT2和MdMYB1受到硝酸盐和其它环境因子的相反调控。此外，作者通过苹果和拟南芥的转基因试验再次对MdBT2基因在花青素生物合成中发挥的重要作用进行了功能鉴定。本文的研究揭示了MdBT2-MdMYB1通路调控苹果花青素生物合成的分子机制，同时可能也适用于其它的植物物种。

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: 28 August, 2018

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