A new transgenic rice line exhibiting enhanced ferric iron reduction and phytosiderophore production confers tolerance to low iron availability in calcareous soil

Iron (Fe) deficiency is a critical agricultural problem, especially in calcareous soil, which is distributed worldwide. Rice plants take up Fe(II) from soil through a OsIRT1 transporter (Strategy I-related system) and also take up Fe(III) via a phytosiderophore-based system (Strategy II system). How...

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Published in:	PloS one Vol. 12; no. 3; p. e0173441
Main Authors:	Masuda, Hiroshi, Shimochi, Erika, Hamada, Tatsuro, Senoura, Takeshi, Kobayashi, Takanori, Aung, May Sann, Ishimaru, Yasuhiro, Ogo, Yuko, Nakanishi, Hiromi, Nishizawa, Naoko K
Format:	Journal Article
Language:	English
Published:	United States Public Library of Science 09-03-2017 Public Library of Science (PLoS)
Subjects:	Acids Barley Biology and Life Sciences Biomass Biosynthesis Biotechnology Calcareous soils Calcium Carbonate - analysis Care and treatment Chelates Crops Ecology and Environmental Sciences Ethanol Fe(III) chelate reductase FMN Reductase - genetics FMN Reductase - metabolism Fodder Gene expression Gene Expression Regulation, Plant - drug effects Health aspects Iron Iron - metabolism Iron - pharmacology Iron deficiency Iron deficiency diseases Medicine and Health Sciences Membrane Transport Proteins - genetics Membrane Transport Proteins - metabolism Nutrient deficiency Oryza Oryza - drug effects Oryza - enzymology Oryza - genetics Oryza - metabolism Oryza sativa Oxidation-Reduction Plants (botany) Plants, Genetically Modified Promoter Regions, Genetic - genetics Reduction Research and Analysis Methods Rice Rice products Secretion Siderophores - metabolism Soil - chemistry Soils Strategy System effectiveness Transcription factors Transgenic plants Yeast Yeasts
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Summary:	Iron (Fe) deficiency is a critical agricultural problem, especially in calcareous soil, which is distributed worldwide. Rice plants take up Fe(II) from soil through a OsIRT1 transporter (Strategy I-related system) and also take up Fe(III) via a phytosiderophore-based system (Strategy II system). However, rice plants are susceptible to low-Fe conditions because they have low Fe(III) reduction activity and low-level phytosiderophore secretion. Previously, we produced transgenic rice plants expressing a mutationally reconstructed yeast ferric chelate reductase, refre1/372, under the control of the OsIRT1 promoter. This transgenic rice line exhibited higher Fe(III) chelate reductase activity and tolerance to Fe deficiency. In addition, we produced transgenic rice overexpressing the Fe deficiency-inducible transcription factor, OsIRO2, which regulates the expression of various genes involved in the strategy II Fe(III) uptake system, including OsNAS1, OsNAAT1, OsDMAS1, OsYSL15, and TOM1. This transgenic rice exhibited improved phytosiderophore secretion ability and tolerance to Fe deficiency. In the present research, transgenic rice plants that possess both the OsIRT1 promoter-refre1/372 and the 35S promoter-OsIRO2 (RI lines) were produced to enhance both Strategy I Fe(II) reductase ability and Strategy II phytosiderophore productivity. RI lines exhibited enhanced tolerance to Fe-deficient conditions at the early and middle-late stages of growth in calcareous soil, compared to both the non-transgenic line and lines harboring either OsIRT1 promoter-refre1/372 or 35S promoter-OsIRO2 alone. RI lines also exhibited a 9-fold higher yield than the non-transgenic line. Moreover, we successfully produced Fe-deficiency-tolerant Tachisugata rice, which is a high-biomass variety used as fodder. Collectively, our results demonstrate that combined enhancement of two Fe uptake systems in rice is highly effective in conferring tolerance to low Fe availability in calcareous soil.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Conceptualization: HM YI YO HN NKN.Data curation: HM ES TH TS.Formal analysis: HM ES TH TS.Funding acquisition: NKN.Investigation: HM ES TH TS MSA.Methodology: HM ES TH TS TK MSA YI HN NKN.Project administration: NKN.Resources: HM TH TK MSA YI YO NKN.Software: HM ES TH TS.Supervision: HM TH TS TK MSA YI HN NKN.Validation: HM TH TS NKN.Visualization: HM ES TH TS MSA.Writing – original draft: HM ES TS.Writing – review & editing: HM TK MSA NKN. Competing Interests: The authors have declared that no competing interests exist.
ISSN:	1932-6203 1932-6203
DOI:	10.1371/journal.pone.0173441