Calcium acetate‐induced reduction of cadmium accumulation in Oryza sativa: Expression of auto‐inhibited calcium‐ATPase and cadmium transporters

Abstract

Calcium (Ca) signalling has an essential role in regulating plant responses to various abiotic stresses.• This study applied Ca in various forms (Ca acetate and CaCl 2 ) and concentrations to reduce cadmium (Cd) concentration in rice and propose a possible mechanism through which Ca acts to control the Cd concentration in rice.• The results showed that supplementation of Cd-contaminated soil with Ca acetate reduced the Cd concentration in rice after exposure for 7 days in both hydroponic and soil conditions. The possible involvement of the auto-inhibited Ca 2+ -ATPase gene (ACA) might act to control the primary signal of the Cd stress response. The messages from ACA3 and ACA13 tended to up-regulate the low-affinity cation transporter (OsLCT1) and down-regulate Cd uptake and the Cd translocation transporter, including the genes, natural resistance-associated macrophage protein 5 (Nramp5) and Zn/ Cd-transporting ATPase 2 (HMA2), which resulted in a reduction in the Cd concentration in rice. After cultivation for 120 days, the application of Ca acetate into Cdcontaminated soil inhibited Cd uptake of rice.• Increasing the Ca acetate concentration in the soil lowered the Cd concentration in rice shoots and grains. Moreover, Ca acetate maintained rice productivity and quality whereas both aspects decreased under Cd stress.

Calcium Plays a Double-Edged Role in Modulating Cadmium Uptake and Translocation in Rice

“…Increasing the external Ca concentration significantly downregulated the expression of OsNRAMP1 and OsNRAMP5 (Figure 3A,B). Likewise, Treesubsuntorn and Thiravetyan [47] also reported a downregulation of OsNRAMP5 in rice plants upon applying calcium acetate (Ca(CH 3 COO) 2 ) in soil. These results proved that Ca could also decrease Cd uptake into rice roots by suppressing the expression of OsNRAMP1 and OsNRAMP5.…”

“…Apart from Cd uptake in the roots, the translocation of Cd from roots to shoots is another critical process controlling the accumulation of Cd in the aboveground tissues of rice plants [1,49]. It has been reported that Ca treatment reduced Cd accumulation in the aboveground parts of rice and Gamblea innovans [47,50]. On the contrary, many other studies revealed that Ca could also induce Cd translocation from roots to shoots in Arabidopsis [51], chamomile [52], and rice [33].…”

“…The major factor giving rise to their role in reducing Cd uptake has been explained as the above Ca amendments potentially increasing soil pH and the stabilization of Cd in contaminated soils [60]. On the other hand, increasing evidence has also shown that the application of Ca regulates Cd uptake, translocation, and accumulation in plants [30][31][32][33][47][48][49][50][51][52]. Indeed, the present study revealed that the high Ca concentration in the nutrient solution could dramatically reduce the net Cd 2+ influx and Cd content in rice roots (Figures 1 and 5A,D), further proving the importance of Ca in reducing Cd uptake in rice.…”

The role of P-type IIA and P-type IIB Ca2+-ATPases in plant development and growth

“…It is also worth noting that while the rice genome is three times larger than that of Arabidopsis, rice had only one sequence (LOC_Os04g516110) with high identity with AtACA8 (72%), AtACA9 (70%), and AtACA10 (70%), suggesting a common ancestry of these proteins in these two species. However, due to their duplication history, it can be also inferred that rice has other types II Ca 2+ -ATPases with less identity to Arabidopsis (Treesubsuntorn and Thiravetyan, 2019).…”

Foliar spraying of calcium acetate alleviates yield loss in rice (Oryza sativa L.) by induced anti‐oxidative defence system under ozone and heat stresses

“…Numerous studies have shown that an increase in cytosolic calcium concentration is one of earliest mechanisms by which plant cells respond to various abiotic stresses such as drought, salt, heat, cold, heavy metal stress, and ozone stress (Evans, McAinsh, Hetherington, & Knight, 2005; Knight, 1999; Li et al, 2016; Niu & Liao, 2016; Reich, Aghajanzadeh, Parmar, Hawkesford, & De Kok, 2018; White & Broadley, 2003). Interestingly, exogenous calcium applications have been reported to ameliorate the adverse effect of stresses on plants in many publications in the last decade (Ahmad et al, 2018; Cha‐um, Singh, Samphumphuang, & Kirdmanee, 2012; Erinle et al, 2016; Naeem et al, 2018; Rahman, Mostofa, Nahar, Hasanuzzaman, & Fujita, 2016; Treesubsuntorn & Thiravetyan, 2019). However, although there are several methods for introducing calcium into plants, there has been nothing reported about foliar spraying calcium directly onto rice leaves under high ozone condition (100 ± 50 ppb).…”