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- Title
<italic>MdWRKY9</italic> overexpression confers intensive dwarfing in the M26 rootstock of apple by directly inhibiting brassinosteroid synthetase <italic>MdDWF4</italic> expression.
- Authors
Zheng, Xiaodong; Zhao, Yu; Shan, Dongqian; Shi, Kun; Wang, Lin; Li, Qingtian; Wang, Na; Zhou, Jingzhe; Yao, Junzhu; Xue, Yuan; Fang, Shuang; Chu, Jinfang; Guo, Yan; Kong, Jin
- Abstract
Summary: Dwarfing rootstocks enable high‐density planting and are therefore highly desirable in modern apple (<italic>Malus domestica</italic>) production. M26 is a semi‐dwarfing rootstock that is used worldwide, but identifying intensive dwarfing rootstock is a major goal of apple breeding programs. Herein, we show that MdWRKY9 mediates dwarfing by directly inhibiting the transcription of the brassinosteroid (BR) rate‐limiting synthetase MdDWF4 and reducing BR production. We found that the transcriptional factor MdWRKY9 is highly expressed in all tested dwarfing rootstocks. Transgenic lines of M26 rootstock overexpressing <italic>MdWRKY9</italic> exhibit further dwarfing, which resulted from the reduced BR levels and was reversed via exogenous brassinolide treatment. Both an <italic>in vivo</italic> chromatin immunoprecipitation (ChIP) analysis and an <italic>in vitro</italic> electrophoretic mobility shift assay (EMSA) indicated that MdWRKY9 binds to the promoter of <italic>MdDWF4</italic>. Furthermore, MdWRKY9 repressed <italic>MdDWF4</italic> expression in stable transgenic apple plants as determined by quantitative PCR. In addition, RNA‐interfered expression of <italic>MdWRKY9</italic> in transiently transformed apple calli led to a significant increase of <italic>MdDWF4</italic>, suggesting MdWRKY9 plays a critical role in regulating the expression of <italic>MdDWF4</italic>. We report a novel dwarfing mechanism in perennial woody plants that involves WRKY‐controlled BR production, and present a new dwarfing M26 rootstock for potential applications in apple production.
- Subjects
GENETIC overexpression; BRASSINOSTEROIDS; LIGASES; ROOTSTOCKS; APPLES
- Publication
New Phytologist, 2018, Vol 217, Issue 3, p1086
- ISSN
0028-646X
- Publication type
Article
- DOI
10.1111/nph.14891