Expression of the Tobacco Non-symbiotic Class 1 Hemoglobin Gene Hb1 Reduces Cadmium Levels by Modulating Cd Transporter Expression Through Decreasing Nitric Oxide and ROS Level in Arabidopsis

Ramin Bahmani; DongGwan Kim; JongDuk Na; Seongbin Hwang

doi:10.3389/fpls.2019.00201

Expression of the Tobacco Non-symbiotic Class 1 Hemoglobin Gene Hb1 Reduces Cadmium Levels by Modulating Cd Transporter Expression Through Decreasing Nitric Oxide and ROS Level in Arabidopsis

Front Plant Sci. 2019 Feb 22:10:201. doi: 10.3389/fpls.2019.00201. eCollection 2019.

Authors

Ramin Bahmani^{1

2

3}, DongGwan Kim^{1

2

3}, JongDuk Na¹, Seongbin Hwang^{1

2

3}

Affiliations

¹ Department of Molecular Biology, Sejong University, Seoul, South Korea.
² Department of Bioindustry and Bioresource Engineering, Sejong University, Seoul, South Korea.
³ Plant Engineering Research Institute, Sejong University, Seoul, South Korea.

Abstract

Hemoglobin (Hb) proteins are ubiquitous in plants, and non-symbiotic class 1 hemoglobin (Hb1) is involved in various biotic and abiotic stress responses. Here, the expression of the tobacco (Nicotiana tabacum) hemoglobin gene NtHb1 in Arabidopsis (Arabidopsis thaliana) showed higher cadmium (Cd) tolerance and lower accumulations of Cd, nitric oxide (NO), and reactive oxygen species (ROS) like hydrogen peroxide (H₂O₂). NtHb1-expressing Arabidopsis exhibited a reduced induction of NO levels in response to Cd, suggesting scavenging of NO by Hb1. In addition, transgenic plants had reduced accumulation of ROS and increased activities of antioxidative enzymes (catalase, superoxide dismutase, and glutathione reductase) in response to Cd. While the expression of the Cd exporters ABC transporter (PDR8) and Ca²⁺/H⁺ exchangers (CAXs) was increased, that of the Cd importers iron responsive transporter 1 (IRT1) and P-type 2B Ca²⁺ ATPase (ACA10) was reduced in response to Cd. When Col-0 plants were treated with the NO donor sodium nitroprusside (SNP) and H₂O₂, the expression pattern of Cd transporters (PDR8, CAX3, IRT1, and ACA10) was reversed, suggesting that NtHb1 expression decreased the Cd level by regulating the expression of Cd transporters via decreased NO and ROS. Correspondingly, NtHb1-expressing Arabidopsis showed increased Cd export. In summary, the expression of NtHb1 reduces Cd levels by regulating Cd transporter expression via decreased NO and ROS levels in Arabidopsis.

Keywords: ACA10; CAX; IRT1; PDR8; ROS; cadmium; hemoglobin; nitric oxide.