Abstract
Abscisic acid (ABA) is known as an important hormone regulating plant stress resistance, such as salt, drought and heavy metal resistance. However, the relationship between ABA and cadmium (Cd) enrichment in ramie (Boehmeria nivea L.) is still unclear to date. This study aimed to reveal the effect of ABA on Cd enrichment in ramie, and we received the following results: (1) Under Cd treatment, the Cd uptake of ramie increased with the increase of Cd concentration, but the chlorophyll content decreased. Under Cd treatment, the ABA content was highest in roots of ramie, followed by that in old leaves, and lowest in new leaves. Long-time treatment of high Cd concentration reduced the ability of endogenous ABA biosynthesis. (2) Spraying ABA on ramie plants (SORP) and adding ABA directly to the culture solution (ADCS) with low concentration can promote the growth of ramie and increase the amount of Cd uptake, and the effect of SORP is better. (3) The molecular reason for the decrease of chlorophyll content due to Cd stress, may be resulted from the down-regulated expression of the chlorophyll synthesis genes (BnPAO and BnNYC1) and the up-regulated expression of the chlorophyll degradation genes (BnCHLH, BnCHLG, BnHAP3A and BnPPR1). The elevated ABA content in ramie plants may due to the up-regulated expression of the ABA synthesis related genes (BnABA1, BnNCED3, and BnNCED5) and the genes (BnABCG40, BnNFXL2, BnPYL9, BnGCR2, BnGTG1, BnBGLU1, BnUTG1, BnVHAG1 and BnABI5) that encoding ABA transport and response proteins, which was consistent with the enhance the Cd uptake in ramie. Our study revealed the relationship between ABA and Cd uptake in ramie, which provided a reference for improving the enrichment of Cd in ramie.
Highlights
Remediation of heavy metals contaminated soil has become an increasingly active field in environmental science research, and a worldwide p roblem[1]
When the Cd concentration was lower than 15 mg L−1, the expression of BnVHAG1 was significantly induced, whereas it was inhibited at 30 mg L−1 of CdCl2 treatment. These results suggested that the changes of Abscisic acid (ABA) content in ramie plants induced by Cd stress may be caused by the differential expression of the ABA biosynthesis, transport and response related genes
It is confirmed that endogenous ABA content in plants would change under cadmium stress, resulting in changes of Cd accumulation in plant
Summary
Remediation of heavy metals contaminated soil has become an increasingly active field in environmental science research, and a worldwide p roblem[1]. Abiotic stress such as drought, cold, high temperature, salt, waterlogging, and heavy metal stress can increase the content of endogenous ABA in plants and enhance stress resistance. It is obvious that the regulation role of ABA in Cd uptake in plants and the application of ABA to improve the efficiency of remediation of heavy metal contaminated soil in agriculture have become one of the hot topics in plant remediation. In order to explore the role of ABA in response to Cd stress and in regulation of Cd uptake in ramie, the ramie variety Zhongzhu No 2 of high Cd enrichment ability was used as material in this study.The pattern of endogenous ABA content of ramie plant under Cd stress and the effects of ABA treatment on Cd absorption in ramie were analyzed
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