Identification and functional analysis of calcium sensor calmodulins from heavy metal hyperaccumulator Noccaea caerulescens

Abstract

Noccaea caerulescens (J. Presl & C. Presl) F. K. Mey. is a heavy metal hyperaccumulator exhibiting extreme tolerance to various environmental stresses. To date, the functional role of Ca2+-binding protein in this plant is largely unknown. To investigate the function of calmodulins (CaMs) in N. caerulescens, CaM2, a Ca2+ sensor encoding gene, was identified and functionally characterised. Protein structure analysis showed that NcCaM2 contains four classic exchange factor (EF)-hand motifs with high sequence similarity to the CaM proteins from model plant Arabidopsis thaliana L. Tissue specific expression analysis showed that NcCaM2 is constitutively expressed in stems, leaves, and roots. Expression level of NcCaM2 was significantly upregulated under various environmental stimulus, indicating a potential involvement of NcCaM2 in the tolerance to abiotic stresses. The heterologous expression of NcCaM2 in a yeast mutant strain increased the heavy metal tolerance in yeast cells. Furthermore, the constitutive expression of NcCaM2 enhanced the heavy metal tolerance capability of transgenic tobacco (Nicotiana tabacum L.) plants. Our data suggested an important role of NcCaM2 in the responses to environmental stresses and provided a potential target gene to enhance of the ability to hyperaccumulate metals.

Effect of Mercuric Ion on the Oxidant Response and Calcium Ion in the Protoplasts of Arabidopsis Thaliana

“…Under the action of an abnormal external environment, the content of Ca 2+ in the cytoplasm will increase, which mainly derives from Ca 2+ in the extracellular environment and calcium reservoir (Toprak et al, 2021). Previously, it is found that heavy metals affected the function of calcium sensor calmodulins (Han et al, 2023) and cadmium affected guard cell regulation by entering the cytosol via Ca 2+ channels (Han et al, 2023). In this study, ion chromatography was used to analyze the effect of heavy metal Hg 2+ on the extracellular Ca 2+ in the Arabidopsis protoplasts.…”