Root Defense in Salicylic Acid-Altering Arabidopsis Plants in Responses to Cadmium Stress
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Root Defense in Salicylic Acid‑Altering Arabidopsis Plants in Responses to Cadmium Stress Qiyu Zhao1 · Chunxiu Gu1 · Yuehang Sun1 · Guangzhe Li1 · Lin‑Lin Li2 · Lin Hao1 Received: 17 October 2019 / Accepted: 7 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The regulatory role of salicylic acid (SA) has been extensively reported in plants subjected to cadmium (Cd) stress. However, the underlying mechanisms still remain to be elucidated. This study provided evidence that root biological processes played crucial roles in SA-altering Arabidopsis plant responses to Cd stress. The nahG (naphthalene hydroxylase G)-transformed plants (with a significantly reduced endogenous SA) displayed a stronger tolerance, while the mutant snc1 (suppressor of nonexpressor of PR gene, constitutive 1; with high endogenous SA) was more sensitive, compared with wild-type (WT) plants under Cd stress. Correspondingly, a stronger antioxidative defense and a weaker oxidative stress were detected in nahG roots, while a more severe oxidative damage occurred in snc1 roots. The expression of a set of redox-related genes was examined, and mostly presented a higher level in nahG roots. A higher content of total flavonoids was observed in nahG roots under Cd stress, which was positively correlated with the expression of flavonoid biosynthesis-related genes. The metal-chelating and -sequestrating genes presented higher expression levels in nahG than in other two genotypes following Cd exposure. Noticeably, the pectin methylesterase inhibitor-encoding genes displayed dramatically high basal expression levels in nahG roots, and further induced under Cd stress. Accordingly, the pectin methylesterase activity was the least in nahG under both control and Cd stress. These results suggest that nahG-conferred Cd tolerance is associated with the root antioxidation defense, flavonoid biosynthesis, metal chelation and sequestration, and cell wall modification. Keywords Salicylic acid · Arabidopsis thaliana · Cadmium chelation · Vacuolar sequestration · Flavonoids · Pectin methylesterification Abbreviations nahG Naphthalene hydroxylase G PC Phytochelatin PCS Phytochelatin synthase PMEI Pectin methylesterase inhibitor SA Salicylic acid snc1 Suppressor of npr1-1 constitutive 1 Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00344-020-10233-x) contains supplementary material, which is available to authorized users. * Lin‑Lin Li [email protected] * Lin Hao [email protected] 1
College of Life Science, Shenyang Normal University, Shenyang 110034, China
College of Environment and Resource, Dalian Nationalities University, Dalian 116605, China
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Introduction Anthropogenic activities and natural events lead to environmental Cd contamination. As a non-essential element, Cd negatively affects plants in almost all life processes. Worse still, it has threaten human health through the food chain. Phytoextraction has been repeatedly addressed as a promisin
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