An HD‐ZIP transcription factor, MxHB13, integrates auxin‐regulated and juvenility‐determined control of adventitious rooting in Malus xiaojinensis. (28th July 2021)

• Record Type: Journal Article
• Authors: Li, Xu; Shen, Fei; Xu, Xiaozhao; Zheng, Qingbo; Wang, Yi; Wu, Ting; Li, Wei; Qiu, Changpeng; Xu, Xuefeng; Han, Zhenhai; Zhang, Xinzhong
• Is Part Of: Plant journal. Volume 107:Number 6(2021)
• Page Start: 1663
• Page End: 1680
• Publication Date: 2021-07-28
• Subjects: adventitious root -- auxin -- Malus xiaojinensis -- SPL26 -- HB13; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.15406
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: Adventitious root (AR) formation is a critical factor in the vegetative propagation of forestry and horticultural plants. Competence for AR formation declines in many species during the miR156/SPL‐mediated vegetative phase change. Auxin also plays a regulatory role in AR formation. In apple rootstock, both high miR156 expression and exogenous auxin application are prerequisites for AR formation. However, the mechanism by which the miR156/SPL module interacts with auxin in controlling AR formation is unclear. In this paper, leafy cuttings of juvenile (Mx‐J) and adult (Mx‐A) phase Malus xiaojinensis were used in an RNA‐sequencing experiment. The results revealed that numerous genes involved in phytohormone signaling, carbohydrate metabolism, cell dedifferentiation, and reactivation were downregulated in Mx‐A cuttings in response to indole butyric acid treatment. Among the differentially expressed genes, an HD‐ZIP transcription factor gene, MxHB13, was found to be under negative regulation of MdSPL26 by directly binding to MxHB13 promoter. MxTIFY9 interacts with MxSPL26 and may play a role in co‐repressing the expression of MxHB13 . The expression of MxTIFY9 was induced by exogenous indole butyric acid. MxHB13 binds to the promoter of MxABCB19‐2 and positively affects the expression. A model is proposed in which MxHB13 links juvenility‐limited and auxin‐limited AR recalcitrance mechanisms in Mx‐A. Significance Statement: Adventitious root (AR) formation is essential for vegetative propagation of perennial woody plants. During the juvenile‐to‐adult phase change mediated by the miR156/SPL, the AR ability decreases dramatically in many species. Auxin also plays a regulatory role in AR formation. However, the mechanism underlying how miR156/SPL module interacts with auxin to regulate AR formation is unclear. Here, we show that an HD‐ZIP transcription factor gene, MxHB13, as a direct target gene of MxSPL26. MxSPL26 interacts with an auxin‐induced MxTIFY9. MxHB13 hence integrates auxin‐regulated and juvenility‐determined control of AR in Malus xiaojinensis .