Characterization of an inducible C2H2-type zinc finger transcription factor VuSTOP1 in rice bean (Vigna umbellata) reveals differential regulation between low pH and aluminum tolerance mechanisms

• Published in: The New phytologist Vol. 208; no. 2; pp. 456 - 468
• Main Authors: Fan, Wei, Lou, He Qiang, Gong, Yu Long, Liu, Mei Ya, Cao, Meng Jie, Liu, Yu, Yang, Jian Li, Zheng, Shao Jian
• Format: Journal Article
• Language: English
• Published: Lancaster New Phytologist Trust 01-10-2015; Wiley Subscription Services, Inc
• Subjects: Aluminium; Aluminum; aluminum (Al) toxicity; Assaying; Beans; citrate secretion; Citric acid; Complementation; Extrusion; Gene expression; Gene regulation; Hydrogen; Localization; Pollution tolerance; Proteins; proton toxicity; Rice; rice bean (Vigna umbellata); Sensitive to Proton Rhizotoxicity1 (STOP1); Transcription; transcriptional regulation; Vigna umbellata; Yeasts; Zinc; Zinc finger proteins
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.13456

The rice bean (Vigna umbellata) root apex specifically secretes citrate through expression activation of Vigna umbellata Multidrug and Toxic Compound Extrusion 1 (VuMATE1) under aluminum (Al3+) stress. However, the underlying mechanisms regulating VuMATE1 expression remain unknown.
We isolated and characterized a gene encoding Sensitive to Proton Rhizotoxicity1 (STOP1)-like protein, VuSTOP1, from rice bean. The role of VuSTOP1 in regulating VuMATE1 expression was investigated using the yeast one-hybrid assay. We characterized the function of VuSTOP1 in Al3
+ - and H+-tolerance using in planta complementation assays.
We demonstrated that VuSTOP1 has transactivation potential. We found that VuSTOP1 expression is inducible by Al3+ and H+ stress. However, although VuSTOP1 binds to the promoter of VuMATE1, the inconsistent tissue localization patterns of VuSTOP1 and VuMATE1 preclude VuSTOP1 as the major factor regulating VuMATE1 expression. In addition, when a protein translation inhibitor increased expression of VuSTOP1, VuMATE1 expression was inhibited. In planta complementation assay demonstrated that VuSTOP1 could fully restore expression of genes involved in H+ tolerance, but could only partially restore expression of AtMATE.
We conclude that VuSTOP1 plays a major role in H+ tolerance, but only a minor role in Al3+ tolerance. The differential transcriptional regulation of VuSTOP1 and VuMATE1 reveals a complex regulatory system controlling VuMATE1 expression.