Identification of a rice metal tolerance protein OsMTP11 as a manganese transporter

PLoS One. 2017 Apr 10;12(4):e0174987. doi: 10.1371/journal.pone.0174987. eCollection 2017.

Abstract

Metal tolerance proteins (MTPs) are a gene family of cation efflux transporters that occur widely in plants and might serve an essential role in metal homeostasis and tolerance. Our research describes the identification, characterization, and localization of OsMTP11, a member of the MTP family from rice. OsMTP11 was expressed constitutively and universally in different tissues in rice plant. Heterologous expression in yeast showed that OsMTP11 complemented the hypersensitivity of mutant strains to Mn, and also complemented yeast mutants to other metals, including Co and Ni. Real time RT-PCR analysis demonstrated OsMTP11 expression was substantially enhanced following 4 h under Cd, Zn, Ni, and Mn treatments, suggesting possible roles of OsMTP11 involvement in heavy metal stress responses. Promoter analysis by transgenic assays with GUS as a reporter gene and mRNA in situ hybridization experiments showed that OsMTP11 was expressed specifically in conducting tissues in rice. DNA methylation assays of genomic DNA in rice treated with Cd, Zn, Ni, and Mn revealed that decreased DNA methylation levels were present in the OsMTP11 promoter region, which was consistent with OsMTP11 induced-expression patterns resulting from heavy metal stress. This result suggested that DNA methylation is one of major factors regulating expression of OsMTP11 through epigenetic mechanisms. OsMTP11 fused to green fluorescent protein (GFP) localized to the entire onion epidermal cell cytoplasm, while vacuolar membrane exhibited increased GFP signals, consistent with an OsMTP11 function in cation sequestration. Our results indicated that OsMTP11 might play vital roles in Mn and other heavy metal transportation in rice.

MeSH terms

  • Amino Acid Sequence
  • Cation Transport Proteins / chemistry
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • CpG Islands
  • Cytoplasm / metabolism
  • DNA Methylation
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Manganese / metabolism*
  • Mutation
  • Onions / metabolism
  • Oryza / genetics
  • Oryza / metabolism*
  • Plant Leaves / metabolism
  • Plant Proteins / chemistry
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Plant Roots / metabolism
  • Promoter Regions, Genetic
  • RNA, Messenger / metabolism
  • Saccharomyces cerevisiae
  • Seeds / metabolism
  • Stress, Physiological / physiology

Substances

  • Cation Transport Proteins
  • Plant Proteins
  • RNA, Messenger
  • Green Fluorescent Proteins
  • Manganese

Grants and funding

This research was supported by the National Natural Sciences Foundation of China (Grant nos. 31271702 and 31570257) and Knowledge Innovation Project for Young Scientists of the South China Botanical Garden, awarded to M. Zhang. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.