Inhibition of ethylene production by putrescine alleviates aluminium-induced root inhibition in wheat plants.

Yan Yu,Chengliang Sun,Weiwei Zhou,Chongwei Jin,Xianyong Lin,Lingli Lu,Jinghong Wang,Yiquan Ye

doi:10.1038/srep18888

Abstract

Inhibition of root elongation is one of the most distinct symptoms of aluminium (Al) toxicity. Although putrescine (Put) has been identified as an important signaling molecule involved in Al tolerance, it is yet unknown how Put mitigates Al-induced root inhibition. Here, the possible mechanism was investigated by using two wheat genotypes differing in Al resistance: Al-tolerant Xi Aimai-1 and Al-sensitive Yangmai-5. Aluminium caused more root inhibition in Yangmai-5 and increased ethylene production at the root apices compared to Xi Aimai-1, whereas the effects were significantly reversed by ethylene biosynthesis inhibitors. The simultaneous exposure of wheat seedlings to Al and ethylene donor, ethephon, or ethylene biosynthesis precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), increased ethylene production and aggravated root inhibition, which was more pronounced in Xi Aimai-1. In contrast, Put treatment decreased ethylene production and alleviated Al-induced root inhibition in both genotypes, and the effects were more conspicuous in Yangmai-5. Furthermore, our results indicated that Al-induced ethylene production was mediated by ACC synthase (ACS) and ACC oxidase, and that Put decreased ethylene production by inhibiting ACS. Altogether, these findings indicate that ethylene is involved in Al-induced root inhibition and this process could be alleviated by Put through inhibiting ACS activity.

Highlights

Ethylene-insensitive mutants demonstrated that the rapidly produced ethylene contributes to Al-induced root inhibition and, relate to Al sensitivity, as demonstrated in Lotus japonicas, Arabidopsis, Glycine max[13,16,17]
We found that the differential Al sensitivity between the wheat genotypes was associated with their different ethylene production capacities, and that Put promoted root growth under Al stress by inhibiting ACC synthase (ACS)-mediated ethylene production
Al tolerance in wheat plants was shown to be highly associated with the TaALMT1-mediated malate exudation from the root tips[2,10]

Summary

Introduction

Ethylene-insensitive mutants demonstrated that the rapidly produced ethylene contributes to Al-induced root inhibition and, relate to Al sensitivity, as demonstrated in Lotus japonicas, Arabidopsis, Glycine max[13,16,17]. It is possible that the discrepancy between the studies is related to different plant species used and the kinetics of ethylene production. Further studies show that under osmotic stress, Put decreased stress-induced ethylene production through reducing the level of reactive oxygen species[26]. Since both of Put and ethylene have been implicated in the regulation of Al-induced root elongation inhibition, it is reasonable to assume that Put may alleviate Al-induced root inhibition, and subsequently Al toxicity through a mechanism of modulating ethylene production. We found that the differential Al sensitivity between the wheat genotypes was associated with their different ethylene production capacities, and that Put promoted root growth under Al stress by inhibiting ACS-mediated ethylene production

Methods

Results

Conclusion