title: Co-overexpression FIT with AtbHLH38 or AtbHLH39 in Arabidopsis-enhanced cadmium tolerance via increased cadmium sequestration in roots and improved iron homeostasis of shoots.
abstract: Cadmium (Cd) is toxic to plant cells. Under Cd exposure, the plant displayed leaf chlorosis, which is a typical symptom of iron (Fe) deficiency. Interactions of Cd with Fe have been reported. However, the molecular mechanisms of Cd-Fe interactions are not well understood. Here, we showed that FER-like Deficiency Induced Transcripition Factor (FIT), AtbHLH38, and AtbHLH39, three basic helix-loop-helix transcription factors involved in Fe homeostasis in plants, also play important roles in Cd tolerance. The gene expression analysis showed that the expression of FIT, AtbHLH38, and AtbHLH39 was up-regulated in the roots of plants treated with Cd. The plants overexpressing AtbHLH39 and double-overexpressing FIT/AtbHLH38 and FIT/AtbHLH39 exhibited more tolerance to Cd exposure than wild type, whereas no Cd tolerance was observed in plants overexpressing either AtbHLH38 or FIT. Further analysis revealed that co-overexpression of FIT with AtbHLH38 or AtbHLH39 constitutively activated the expression of Heavy Metal Associated3 (HMA3), Metal Tolerance Protein3 (MTP3), Iron Regulated Transporter2 (IRT2), and Iron Regulated Gene2 (IREG2), which are involved in the heavy metal detoxification in Arabidopsis (Arabidopis thaliana). Moreover, co-overexpression of FIT with AtbHLH38 or AtbHLH39 also enhanced the expression of NICOTIANAMINE SYNTHETASE1 (NAS1) and NAS2, resulting in the accumulation of nicotiananamine, a crucial chelator for Fe transportation and homeostasis. Finally, we showed that maintaining high Fe content in shoots under Cd exposure could alleviate the Cd toxicity. Our results provide new insight to understand the molecular mechanisms of Cd tolerance in plants.
authors.affiliation: The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Huilan
authors.initials: H
authors.lastname: Wu
authors.forename: Chunlin
authors.initials: C
authors.lastname: Chen
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Hongfei
authors.initials: H
authors.lastname: Liu
authors.forename: Yan
authors.initials: Y
authors.lastname: Cui
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yujing
authors.initials: Y
authors.lastname: He
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Wang
authors.forename: Chengcai
authors.initials: C
authors.lastname: Chu
authors.forename: Zongyun
authors.initials: Z
authors.lastname: Feng
authors.forename: Junming
authors.initials: J
authors.lastname: Li
authors.forename: Hong-Qing
authors.initials: HQ
authors.lastname: Ling
mesh_terms: D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D002104:Cadmium / Q000378:metabolism / Q000633:toxicity*; D006706:Homeostasis; D007501:Iron / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002104:Cadmium; D007501:Iron; C501411:FIT1 protein, Arabidopsis