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Article|01 Sep 2020|OPEN
Auxin regulation and MdPIN expression during adventitious root initiation in apple cuttings
Ling Guan1,2, Yingjun Li1, Kaihui Huang1 & Zong-Ming (Max) Cheng1,3,
1College of Horticulture, Nanjing Agricultural University, 210095 Nanjing, China
2Institute of Pomology, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, 210014 Nanjing, China
3Department of Plant Sciences, University of Tennessee, Knoxville, TN 37831, USA

Horticulture Research 7,
Article number: 143 (2020)
doi: 10.1038/hortres.2020.143
Views: 388

Received: 17 Apr 2020
Revised: 08 Jun 2020
Accepted: 11 Jun 2020
Published online: 01 Sep 2020


Adventitious root (AR) formation is critical for the efficient propagation of elite horticultural and forestry crops. Despite decades of research, the cellular processes and molecular mechanisms underlying AR induction in woody plants remain obscure. We examined the details of AR formation in apple (Malus domestica) M.9 rootstock, the most widely used dwarf rootstock for intensive production, and investigated the role of polar auxin transport in postembryonic organogenesis. AR formation begins with a series of founder cell divisions and elongation of the interfascicular cambium adjacent to vascular tissues. This process is associated with a relatively high indole acetic acid (IAA) content and hydrolysis of starch grains. Exogenous auxin treatment promoted this cell division, as well as the proliferation and reorganization of the endoplasmic reticulum and Golgi membrane. In contrast, treatment with the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) inhibited cell division in the basal region of the cuttings and resulted in abnormal cell divisions during the early stage of AR formation. In addition, PIN-FORMED (PIN) transcripts were differentially expressed throughout the whole AR development process. We also detected upregulation of MdPIN8 and MdPIN10 during induction; upregulation of MdPIN4, MdPIN5, and MdPIN8 during extension; and upregulation of all MdPINs during AR initiation. This research provides an improved understanding of the cellular and molecular underpinnings of the AR process in woody plants.