Regulating role of abscisic acid on cadmium enrichment in ramie (Boehmeria nivea L.)

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.

Abscisic acid: Metabolism, transport, crosstalk with other plant growth regulators, and its role in heavy metal stress mitigation

“…Further, Cd stress increased ABA content more in roots than old leaves of Boehmeria nivea L., with the lowest levels in new leaves. Long-time treatment of high Cd concentrations decreased endogenous ABA biosynthesis (Chen et al, 2021). HM compete with other metal ions and depolarize membrane-inducing Ca 2+ 10.3389/fpls.…”

The regulatory role of abscisic acid on cadmium uptake, accumulation and translocation in plants

“…Only the mechanisms of Brassica chinensis and Populus euphratica were explicated as that ABA elevated antioxidant enzyme activity and reduced the intracellular H 2 O 2 content by enhancing the antioxidant capacity of plants, which was responsible for regulating the entry of Cd through the calcium ion channel, thus leading to a reduction in the level of Cd uptake ( Han et al, 2016 ; Pan et al, 2019 ). However, in Solanum photeinocarpum and Boehmeria nivea , ABA enhanced the Cd uptake mainly by increasing the chlorophyll level and biomass of the plants ( Wang et al, 2016 ; Chen et al, 2021 ). Apart from species, different ABA concentrations showed different effects on the Cd uptake capacity of the same plant.…”

“…Apart from species, different ABA concentrations showed different effects on the Cd uptake capacity of the same plant. In Boehmeria nivea and Solanum photeinocarpum , the strongest Cd uptake was observed at the application of 5 and 20 μM of ABA, respectively, however, the relevant mechanisms involved are not clearly explored ( Wang et al, 2016 ; Chen et al, 2021 ). Although application of ABA also promoted Cd uptake of Bidens Pilosa , it diminished the biomass and chlorophyll content ( Liu L. et al, 2017 ), which was the exact contrast to its effect on stimulating the growth of Solanum photeinocarpum and Boehmeria nivea and other spices.…”

“…In Sedum alfredii , the higher ABA concentration (0.2 mg/L) inhibited the root biomass, but promoted the uptake and accumulation of Cd ( Lu et al, 2020b ). However, in other plants, such as ramie ( Boehmeria nivea L.), purple flowering stalk and Solanum poteinocarpum , lower level of ABA can simultaneously promote root development and Cd uptake and accumulation ( Wang et al, 2016 ; Shen et al, 2017 ; Chen et al, 2021 ). In addition, the significantly root biomass improvement and higher Cd uptake capacity were observed in Sedum alfredii with the application of ABA-catabolizing bacterium Rhodococcus qingshengii ( Wu et al, 2020 ; Du et al, 2022 ).…”

“…Recent studies have established that ABA is closely related to abiotic stresses such as drought ( Lim et al, 2015 ), salinity ( Hussain et al, 2021 ), nutrient deficiency ( Cutler et al, 2010 ), and heavy metals ( Hu et al, 2020 ). According to certain studies, ABA was found to promote the uptake and translocation of Cd in plants ( Wang et al, 2016 ; Liu L. et al, 2017 ; Chen et al, 2021 ), while other studies showed that ABA inhibited Cd uptake and translocation ( Tao et al, 2019 ; Zhang P. et al, 2019 ; Leng et al, 2021 ). To date, the mechanism of ABA in response to the Cd stress of plants is still not well-established.…”