Inducing Ni sensitivity in the Ni hyperaccumulator plant Alyssum inflatum Nyárády (Brassicaceae) by transforming with CAX1, a vacuolar membrane calcium transporter

Abstract

The importance of calcium in nickel tolerance was studied in the nickel hyperaccumulator plant Alyssum inflatum by gene transformation of CAX1, a vacuolar membrane transporter that reduces cytosolic calcium. CAX1 from Arabidopsis thaliana with a CaMV35S promoter accompanying a kanamycin resistance gene was transferred into A. inflatum using Agrobacterium tumefaciens. Transformed calli were sub‐cultured three times on kanamycin‐rich media and transformation was confirmed by PCR using a specific primer for CAX1. At least 10 callus lines were used as a pool of transformed material. Both transformed and untransformed calli were treated with varying concentrations of either calcium (1–15 mM) or nickel (0–500 µM) to compare their responses to those ions. Increased external calcium generally led to increased callus biomass, however, the increase was greater for untransformed callus. Further, increased external calcium led to increased callus calcium concentrations. Transformed callus was less nickel tolerant than untransformed callus: under increasing nickel concentrations callus relative growth rate was significantly less for transformed callus. Transformed callus also contained significantly less nickel than untransformed callus when exposed to the highest external nickel concentration (200 µM). We suggest that transformation with CAX1 decreased cytosolic calcium and resulted in decreased nickel tolerance. This in turn suggests that, at low cytosolic calcium concentrations, other nickel tolerance mechanisms (e.g., complexation and vacuolar sequestration) are insufficient for nickel tolerance. We propose that high cytosolic calcium is an important mechanism that results in nickel tolerance by nickel hyperaccumulator plants.

Impacts of Cd on Temporal Dynamics of Nutrient Distribution Pattern of Bletilla striata, a Traditional Chinese Medicine Plant

“…Zinc was the most significant antagonistic factor to Cd. The antagonistic interaction of the translocation factors of Zn and Cd is predictable, because Cd can enter the plants cells by competing for transporter and channel protein [34,35].Thus, Cd uptake is related to cation absorption, and Cd accumulation will be reduced when abundant divalent cations are present. The tubers demonstrated the highest Zn accumulation at a Cd dose of 1.00 mg/kg (II) in the first year (T 1 ) and at a Cd dose of 0.37 mg/kg (I) in the second year (T 2 ), except T 2-7 .…”

A global forum on ultramafic ecosystems: from ultramafic ecology to rehabilitation of degraded environments

“…The first article reports on an experimental study of the physiology of the Ni-hyperaccumulator Leptoplax emarginata (Brassicaceae), and the results show that the highest Ni concentrations are in the actively transpiring young, thin leaves with the greatest stomatal densities (Bartoli et al 2018). In another study (Ghasemi et al 2018) investigating the role of the CAX1 Ca 2+ vacuole transporter in the Ni-hyperaccumulator Alyssum inflatum (Brassicaceae), it is concluded that high cytosolic Ca 2+ is an important parameter that results in Ni tolerance. An investigation of the mechanisms involved in Mn hyperaccumulation by Phytolacca americana suggests that this trait may be a side effect of rhizosphere acidification as a phosphorus-acquisition mechanism, rather than an adaptation to high soil Mn per se (DeGroote et al 2018).…”

Native Metallophytes on Ultramafic Wooded Grassland in Sta Cruz, Mindoro Occidental, Philippines: Insights Into Phytostabilization and Forest Restoration

“…The same authors emphasized the importance of Calcium for normal plant physiological functioning and survival. In western Iran, the survival rate of a serpentine-endemic Alyssum inflatum was reduced at Ca: Mg = 0.4 ratio and maximum at Ca: Mg = 2 (Ghasemi et al, 2018). However, the authors further noted that at a higher Ca: Mg ratio (i.e., > 20) (Wahsha et al, 2012).…”