Boron Alleviates Aluminum Toxicity by Promoting Root Alkalization in Transition Zone via Polar Auxin Transport. Issue 3 (21st May 2018)

• Record Type: Journal Article
• Authors: Li, Xuewen; Li, Yalin; Mai, Jingwen; Tao, Lin; Qu, Mei; Liu, Jiayou; Shen, Renfang; Xu, Guilian; Feng, Yingming; Xiao, Hongdong; Wu, Lishu; Shi, Lei; Guo, Shaoxue; Liang, Jian; Zhu, Yiyong; He, Yongming; Balu¡ka, Franti¡ek; Shabala, Sergey; Yu, Min
• Is Part Of: Plant physiology. Volume 177:Issue 3(2018)
• Page Start: 1254
• Page End: 1266
• Publication Date: 2018-05-21
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.18.00188
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Boron promotes PIN2-based polar auxin transport in the apical transition zone of pea (Pisum sativum) roots, leading to root alkalization and thereby reducing aluminum toxicity. Abstract: Boron (B) alleviates aluminum (Al) toxicity in higher plants; however, the underlying mechanisms behind this phenomenon remain unknown. Here, we used bromocresol green pH indicator, noninvasive microtest, and microelectrode ion flux estimation techniques to demonstrate that B promotes root surface pH gradients in pea ( Pisum sativum ) roots, leading to alkalization in the root transition zone and acidification in the elongation zone, while Al inhibits these pH gradients. B significantly decreased Al accumulation in the transition zone (∼1.0–2.5 mm from the apex) of lateral roots, thereby alleviating Al-induced inhibition of root elongation. Net indole acetic acid (IAA) efflux detected by an IAA-sensitive platinum microelectrode showed that polar auxin transport, which peaked in the root transition zone, was inhibited by Al toxicity, while it was partially recovered by B. Electrophysiological experiments using the Arabidopsis ( Arabidopsis thaliana ) auxin transporter mutants ( auxin resistant1-7 ; pin-formed2 [ pin2 ]) and the specific polar auxin transporter inhibitor1-naphthylphthalamic acid showed that PIN2-based polar auxin transport is involved in root surface alkalization in the transition zone. Our results suggest that B promotes polar auxin transport driven by the auxin efflux transporter PIN2 and leads to the downstream regulation of the plasma membrane-H + -ATPase, resulting in elevated root surface pH, which is essential to decrease Al accumulation in this Al-targeted apical root zone. These findings provide a mechanistic explanation for the role of exogenous B in alleviation of Al accumulation and toxicity in plants.