Zhao Qiang, Ren Yi-Ran, Wang Qing-Jie, Yao Yu-Xin, You Chun-Xiang, Hao Yu-Jin
National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, China.
Plant Biotechnol J. 2016 Jul;14(7):1633-45. doi: 10.1111/pbi.12526. Epub 2016 Jan 23.
Fe deficiency is a widespread nutritional disorder in plants. The basic helix-loop-helix (bHLH) transcription factors (TFs), especially Ib subgroup bHLH TFs which are involved in iron uptake, have been identified. In this study, an IVc subgroup bHLH TF MdbHLH104 was identified and characterized as a key component in the response to Fe deficiency in apple. The overexpression of the MdbHLH104 gene noticeably increased the H(+) -ATPase activity under iron limitation conditions and the tolerance to Fe deficiency in transgenic apple plants and calli. Further investigation showed that MdbHLH104 proteins bonded directly to the promoter of the MdAHA8 gene, thereby positively regulating its expression, the plasma membrane (PM) H(+) -ATPase activity and Fe uptake. Similarly, MdbHLH104 directly modulated the expression of three Fe-responsive bHLH genes, MdbHLH38, MdbHLH39 and MdPYE. In addition, MdbHLH104 interacted with 5 other IVc subgroup bHLH proteins to coregulate the expression of the MdAHA8 gene, the activity of PM H(+) -ATPase and the content of Fe in apple calli. Therefore, MdbHLH104 acts together with other apple bHLH TFs to regulate Fe uptake by modulating the expression of the MdAHA8 gene and the activity of PM H(+) -ATPase in apple.
缺铁是植物中一种普遍存在的营养失调现象。已经鉴定出了基本的螺旋-环-螺旋（bHLH）转录因子（TFs），尤其是参与铁吸收的Ib亚组bHLH TFs。在本研究中，鉴定出了一个IVc亚组bHLH TF MdbHLH104，并将其表征为苹果对缺铁响应中的关键成分。MdbHLH104基因的过表达在铁限制条件下显著提高了转基因苹果植株和愈伤组织中的H(+) -ATPase活性以及对缺铁的耐受性。进一步研究表明，MdbHLH104蛋白直接与MdAHA8基因的启动子结合，从而正向调节其表达、质膜（PM）H(+) -ATPase活性和铁吸收。同样，MdbHLH104直接调节三个铁响应bHLH基因MdbHLH38、MdbHLH39和MdPYE的表达。此外，MdbHLH104与其他5个IVc亚组bHLH蛋白相互作用，共同调节MdAHA8基因的表达、PM H(+) -ATPase的活性以及苹果愈伤组织中铁的含量。因此，MdbHLH104与其他苹果bHLH TFs共同作用，通过调节MdAHA8基因的表达和苹果中PM H(+) -ATPase的活性来调节铁的吸收。
