Effect of indole-3-acetic acid on aluminum-induced efflux of malic acid from wheat (Triticum aestivum L.)

Abstract

Indole-3-acetic acid (IAA) has been found to be involved in plant resistance to various types of environmental stress. Aluminum (Al) toxicity, as one of the most important environmental stress in acid soils, is coped by most plants through the efflux of organic acids via anion channel. This study aims to evaluate the effect of IAA on efflux of malic acid from wheat (Triticum aestivum L.) under Al stress. Hydroponic experiments were performed by wheat ET8 (Al-tolerant). The efflux of malic acid was investigated under different treatments. Results showed that Al treatments increased the accumulation of endogenous IAA, but decreased the activity of IAA oxidase in a dose-dependent manner. A good correlation between all the data of malic acid efflux rate and endogenous IAA content was obtained (R 2 = 0.9859**). IAA treatment alone had no effect on the efflux of malic acid. But compared to Al (50 μM) treatment, the efflux of malic acid increased significantly under the co-treatment of IAA (50 μM) and Al (50 μM). In split-root experiments, the root with half of it being treated with Al (CK/Al), the other part (CK) showed significantly higher malic acid efflux rate and endogenous IAA content in root apexes, compared with the root without such treatment (CK/CK). The Al-induced malic acid efflux decreased under the treatments of IAA transport inhibitor N-1-napthyl-phtalamic acid (NPA) (or 2,3,5-triiodobenzoic acid, TIBA). These above results suggested the possible involvement of IAA in the stimulation of malic acid efflux under Al stress. In addition, anion channel inhibitor treatment experiment showed that IAA (50 μM) relieved the inhibiting effect of 5 μM anthracene-9-carboxylic acid (A9C) (or niflumic acid, NIF) on malic acid efflux induced by Al (50 μM), compared to the cotreatment of Al (50 μM) and 5 μM anion channel inhibitor A9C (or NIF) it is thus speculated that the anion channel might have been activated when IAA was involved in malic acid efflux. This study showed that IAA was involved in aluminuminduced efflux of malic acid from wheat.

Ethylene negatively regulates aluminium-induced malate efflux from wheat roots and tobacco cells transformed with TaALMT1

“…Similar to our results, the authors found that the Al 3+ -induced malate efflux is inhibited by antagonists of auxin polar transport (TIBA; 2,3,5-triiodobenzoic acid, and NPA; naphthylphthalamic acid), and anion channel blockers (niflumate and A-9-C) (Yang et al , 2011). A close crosstalk between ethylene and auxin in regulation of root growth and development has been reported in the literature (see review of Stepanova and Alonso, 2009).…”

Sucrose transporter NtSUT1 confers aluminum tolerance on cultured cells of tobacco (Nicotiana tabacumL.)

“…Auxin enhanced the expression level of the TaALMT1 and thereby increased the Al tolerance (Y. Yang et al 2011). The AtALMT1 was also reported to be regulated by phytohormones such as auxin and abscisic acid (Kobayashi et al 2013).…”

Role of ROS and auxin in plant response to metal-mediated stress

“…18 For example, Al alters both auxin accumulation and distribution in plants under Al stress. 12,[27][28][29] These changes are mediated by Al-inhibited auxin transport form distal transition zone to elongation zone of the maize primary root, resulting in an arrest of root elongation. 27 Further studies demonstrate that the alteration of auxin transport for Al-induced auxin redistribution is modulated by auxin carriers AUX1 and PIN2.…”