Effects of the Dark Septate Endophyte (DSE) Exophiala pisciphila on the Growth of Root Cell Wall Polysaccharides and the Cadmium Content of Zea mays L. under Cadmium Stress.

Yao Xiao,Yong-Mei He,Fang-Dong Zhan,Guang-Qun Zhang,Zhi-Xin Yang,Meng-Xue Dai

doi:10.3390/jof7121035

Yao Xiao, Yong-Mei He + Show 4 more

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https://doi.org/10.3390/jof7121035

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Abstract

This paper aims to investigate the mechanism by which dark septate endophytes (DSEs) enhance cadmium (Cd) tolerance in there host plants. Maize (Zea mays L.) was inoculated with a DSE, Exophiala pisciphila, under Cd stress at different concentrations (0, 5, 10, and 20 mg·kg−1). The results show that, under 20 mg/kg Cd stress, DSE significantly increased maize biomass and plant height, indicating that DSE colonization can be utilized to increase the Cd tolerance of host plants. More Cd was retained in DSE-inoculated roots, especially that fixed in the root cell wall (RCW). The capability of DSE to induce a higher Cd holding capacity in the RCW is caused by modulation of the total sugar and uronic acid of DSE-colonized RCW, mainly the pectin and hemicellulose fractions. The fourier-transform spectroscopy analysis results show that carboxyl, hydroxyl, and acidic groups are involved in Cd retention in the DSE-inoculated RCW. The promotion of the growth of maize and improvement in its tolerance to Cd due to DSEs are related to restriction of the translocation of Cd from roots to shoots; resistance of Cd uptake Cd inside cells; and the increase in RCW-integrated Cd through modulating RCW polysaccharide components.

Highlights

Cadmium (Cd) is a widespread environmental pollutant with acute and chronic toxicity in plants and animals [1]
All inoculated treatments were successfully colonized by E. pisciphila with a range of 15% to 35% colonization and dark septate endophytes (DSEs) structures were not observed in the roots of noninoculated maize
The results showed that inoculation of DSE affected (p < 0.05) hemicellulose 1 (HE1) uronic acid and hemicellulose 2 (HE2) uronic acid, while the uronic acid content of PE was very significantly affected by DSE treatment

Summary

Introduction

Cadmium (Cd) is a widespread environmental pollutant with acute and chronic toxicity in plants and animals [1]. Under aluminum (Al) stress, the lignin synthesis pathway of rice roots is enhanced, leading to cell wall thickenings to immobilize the Al [24]. PE and HE are already accepted to play essential roles in binding divalent or trivalent heavy metal cations which principally rely on the number of acidic mucopolysaccharides and uronic acids. These cell wall components provide binding and adsorption sites for heavy metals before crossing the cell membrane leading to less plant heavy metal accumulation in the cytoplasm [18,29,31,32,33,34,35,36,37,38]. The relationship between Cd accumulation and cell wall components in maize requires further investigation

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