Abstract
Tobacco (Nicotiana tabacum L.) is the most important non-food cash crop worldwide and has recently been considered a Cd hyperaccumulator. Metallothionein, a small–molecular weight protein with cysteine-rich domains, plays a key role in plant growth, development, and maintenance of metal homeostasis. The understanding of the tobacco metallothionein (MT) gene family remains unclear. Herein, we systematically characterized twelve NtMT genes in the tobacco genome and classified them into three phylogenetic subfamilies. A number of cis-elements related to plant responses to hormones and abiotic stresses were detected in the promoters of NtMT genes. Tissue expression pattern analysis indicated that NtMT4A/4B were expressed only in seeds, and NtMT2C/2F/2G were mainly expressed in roots. Moreover, most of the NtMT genes were highly induced by heavy metal stress and ion deficiency, suggesting their critical role in relieving metal toxicity and maintaining ion homeostasis in tobacco. This was the first study to describe the genome-wide analysis of the NtMT gene family in tobacco, and the results lay a foundation for understanding the functions of NtMT genes for further enhancing plant tolerance to heavy metal toxicity.
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Abbreviations
- MT:
-
metallothionein
- ROS:
-
reactive oxygen species
- qPCR:
-
quantitative polymerase chain reaction
- CDS:
-
coding sequence
- HMM:
-
hidden Markov model
- GSDS:
-
Gene Structure Display Server
- EC:
-
early cysteine-labeled
- Cq:
-
cycle quantification
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Funding
This work was supported by the Chongqing Research Program of Basic Research and Frontier Technology (cstc2019jcyj-msxmX0429), the Science and Technology Research Program of Chongqing Municipal Education Commission (KJZD-K202001504, KJQN201901547, and KJQN201901523), the Venture & Innovation Support Program for Chongqing Overseas Returnees (cx2019131), the National Undergraduate Training Programs for Innovation and Entrepreneurship of China (201911551001), and the Graduate Science and Technology Innovation Program Project of CQUST (YKJCX1920501, YKJCX1920505).
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Key Message
Twelve NtMTs were identified and bioinformatically analyzed in tobacco. NtMT4A/4B were specifically expressed in seeds. Cadmium increased most of NtMTs’ expression, and NtMT3 were involved in responding to copper stress. The essential metal deficiency expression pattern implied that NtMTs play important roles in regulating metal homeostasis in tobacco.
Supplementary Information
Figure S1
Phylogenetic tree of MT proteins in N. tabacum and Arabidopsis. The tree was generated using MEGA X software by the neighbor-joining method with 1000 bootstrap replicates. The four subfamilies are shown in different colors by iTOL. (PNG 3493 kb)
Figure S2
Motif logos of NtMT proteins. (PNG 8862 kb)
Figure S3
Visual representation of cis-elements in the promoters of tobacco NtMT genes by shading. (PNG 6487 kb)
Figure S4
Heatmap showing the abundance of NtMT gene transcripts in different tissues of tobacco. The blue and red shades indicate lower and higher accumulation of transcripts, respectively. (PNG 2657 kb)
Table S1
The primers used for the real-time quantitative PCR. (DOCX 15 kb)
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Yu, Q., He, L., Huo, C. et al. Genome-Wide Identification and Expression Analysis of Heavy Metal Stress–Responsive Metallothionein Family Genes in Nicotiana tabacum. Plant Mol Biol Rep 39, 443–454 (2021). https://doi.org/10.1007/s11105-020-01262-7
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DOI: https://doi.org/10.1007/s11105-020-01262-7