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

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.

Genome-Wide Identification and Expression Analysis of the Cation Diffusion Facilitator Gene Family in Turnip Under Diverse Metal Ion Stresses

“…Although increasing functional studies on plant MTP members have been reported in diverse species, such as Arabidopsis thaliana ( Desbrosses-Fonrouge et al, 2005 ; Delhaize et al, 2007 ; Eroglu et al, 2016 , 2017 ), Oryza sativa ( Menguer et al, 2013 ; Zhang and Liu, 2017 ), Brassica juncea ( Xu et al, 2009 ; Lang et al, 2011 ), Cucumis sativus ( Migocka et al, 2015a , b ), Thlaspi goesingense ( Kim et al, 2004 ), and Camellia sinensis ( Li Q.H. et al, 2017 ), the understanding of the roles of the MTP family is still significantly limited.…”

“…This relationship indicates some functional differentiation between MTP9/10 and MTP11 proteins ( Gustin et al, 2011 ). Several MTP11 transporters from different species confer Mn 2+ tolerance ( Delhaize et al, 2007 ; Zhang and Liu, 2017 ), whereas limited evidence of the involvement of MTP9/10 proteins in Mn transport or tolerance to Mn is currently available ( Migocka et al, 2015b ), though they are also classified as Mn-CDFs. Current studies generally indicated that MTP proteins contribute to the detoxification of heavy metals and promote their accumulation ( Kim et al, 2004 ; Delhaize et al, 2007 ; Xu et al, 2009 ; Lang et al, 2011 ; Menguer et al, 2013 ; Migocka et al, 2015a , b ; Eroglu et al, 2017 ; Li Q.H.…”

“…Current studies generally indicated that MTP proteins contribute to the detoxification of heavy metals and promote their accumulation ( Kim et al, 2004 ; Delhaize et al, 2007 ; Xu et al, 2009 ; Lang et al, 2011 ; Menguer et al, 2013 ; Migocka et al, 2015a , b ; Eroglu et al, 2017 ; Li Q.H. et al, 2017 ; Zhang and Liu, 2017 ). The functions of MTPs or other metal transporters in heavy metal hyperaccumultors may improve phytoremediation efficiency ( Kim et al, 2004 ; Gustin et al, 2009 ).…”

Manganese in Plants: From Acquisition to Subcellular Allocation

“…Another MTP11 ortholog in rice, OsMTP11, was also described to be involved in Mn detoxification. OsMTP11 is induced by high Mn and expressed specifically in conducting tissues (Zhang and Liu, 2017). Interestingly, epigenetic mechanisms (e.g., DNA methylation) were a major factor regulating the expression level of OsMTP11 (Zhang and Liu, 2017).…”

“…OsMTP11 is induced by high Mn and expressed specifically in conducting tissues (Zhang and Liu, 2017). Interestingly, epigenetic mechanisms (e.g., DNA methylation) were a major factor regulating the expression level of OsMTP11 (Zhang and Liu, 2017). Knockdown of OsMTP11 resulted in growth inhibition in the presence of high concentrations of Mn 2+ and also led to increased accumulation of Mn in shoots and roots.…”