Liu Yanfei, Ma Kangxun, Qi Yingwei, Lv Guowen, Ren Xiaolin, Liu Zhande, Ma Fengwang
College of Horticulture, Northwest A&F University, Yangling, 712100 Shannxi, China.
College of Life Science, Northwest A&F University, Yangling, 712100 Shannxi, China.
J Agric Food Chem. 2021 Mar 31;69(12):3677-3691. doi: 10.1021/acs.jafc.0c07037. Epub 2021 Mar 22.
The anthocyanin synthetic pathway is regulated centrally by an MYB-bHLH-WD40 (MBW) complex. Anthocyanin pigmentation is an important fruit quality trait in red-fleshed kiwifruit; however, the underlying regulatory mechanisms involving the MBW complex are not well understood. In this study, one R2R3MYB ( expressed in fruit characteristically), one bHLH (), two upstream regulators of ( and ), and one WDR () are characterized as being involved in the regulation of anthocyanin synthesis in kiwifruit. plays an important role in the regulation of anthocyanin accumulation by specifically activating the promoters of several anthocyanin pathway genes including , ', , , , and . Coexpression of , , or together with induces much greater anthocyanin accumulation in both tobacco leaves and in fruit compared with alone. Moreover, this activation is further enhanced by adding . We found that both AcMYBF110 and AcWDR1 interact with all three AcbHLH factors, while AcMYBF110 also interacts with AcWDR1 to form three different MBW complexes that have different regulatory roles in anthocyanin accumulation of kiwifruit. The AcMYBF110-AcbHLH1-AcWDR1 complex directly targets the promoters of anthocyanin synthetic genes. Other features of the regulatory pathways identified include promotion of , and activities by this MBW complex, providing for both reinforcement and feedback regulation, whereas the AcMYBF110-AcbHLH4/5-AcWDR1 complex is indirectly involved in the regulation of anthocyanin synthesis by activating the promoters of and to amplify the regulation signals of the first MBW complex.
花青素合成途径由MYB-bHLH-WD40（MBW）复合体进行核心调控。花青素色素沉着是红肉猕猴桃重要的果实品质性状；然而，涉及MBW复合体的潜在调控机制尚不清楚。在本研究中，一个R2R3MYB（在果实中特异性表达）、一个bHLH、两个WD40（WD40-1和WD40-2）的上游调控因子以及一个WDR被鉴定为参与猕猴桃花青素合成的调控。AcMYBF110通过特异性激活包括CHS、CHI、F3H、F3'H、DFR和ANS在内的几个花青素途径基因的启动子，在花青素积累的调控中发挥重要作用。与单独的AcMYBF110相比，AcMYBF110与AcbHLH1、AcbHLH4或AcbHLH5共表达可在烟草叶片和猕猴桃果实中诱导更多的花青素积累。此外，添加蔗糖可进一步增强这种激活作用。我们发现AcMYBF110和AcWDR1均与所有三个AcbHLH因子相互作用，而AcMYBF110也与AcWDR1相互作用形成三种不同的MBW复合体，它们在猕猴桃花青素积累中具有不同的调控作用。AcMYBF110-AcbHLH1-AcWDR1复合体直接靶向花青素合成基因的启动子。所鉴定的调控途径的其他特征包括该MBW复合体促进CHS、CHI和F3H的活性，从而实现增强和反馈调节，而AcMYBF110-AcbHLH4/5-AcWDR1复合体通过激活UFGT和ANS的启动子间接参与花青素合成的调控，以放大第一个MBW复合体的调控信号。
