Tolerance to excess-boron conditions acquired by stabilization of a BOR1 variant with weak polarity in Arabidopsis

Shinji Wakuta, Teppei Fujikawa, Satoshi Naito, Junpei Takano

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Boron (B) is a metalloid that is essential for plant growth but is toxic when present in excess. Arabidopsis BOR1 is a borate exporter, facilitating B translocation from root to shoot under limited-B conditions. BOR1 shows stele side polar localization in the plasma membrane of various root cells, presumably to support B translocation toward the stele. BOR1 is degraded under high-B supply through vacuolar sorting via ubiquitination at the K590 residue to prevent the accumulation of B to a toxic level in shoots. A previous study showed that overexpression of BOR1 under control of the cauliflower mosaic virus 35S RNA promoter improved the growth of Arabidopsis under limited-B conditions without affecting the growth under sufficient-to-excess-B conditions. In this study, we unexpectedly found that ubiquitous expression of a stabilized BOR1 variant improved tolerance to excess-B in Arabidopsis. We established transgenic plants expressing BOR1-GFP fused with hygromycin phosphotransferase (HPT) and BOR1(K590A)-GFP-HPT under control of the ubiquitin 10 promoter. BOR1-GFP-HPT and BOR1(K590A)-GFP-HPT were expressed in various cell types in leaves and roots and showed weak polar localization in root tip cells. BOR1-GFP-HPT, but not BOR1(K590A)-GFP-HPT, was degraded through an endocytic pathway under high-B conditions. Transgenic plants with the stabilized variant BOR1(K590A)-GFP-HPT showed improved root and shoot growth under excess-B conditions. The concentration of B was greater in the shoots of plants with BOR1(K590A)-GFP-HPT or BOR1-GFP-HPT than in those of untransformed wild-type plants. These results suggest that BOR1(K590A)-GFP-HPT confers tolerance to excess-B by excluding B from the cytosol of shoot cells. Results from this study indicate the potential for engineering the trafficking properties of a transporter to produce plants that are tolerant to mineral stress.

Original languageEnglish (US)
Article number4
JournalFrontiers in Cell and Developmental Biology
Volume4
Issue numberFEB
DOIs
StatePublished - Feb 3 2016
Externally publishedYes

Fingerprint

hygromycin-B kinase
Boron
Arabidopsis
Poisons
Genetically Modified Plants
Growth
Metalloids
Plant Shoots
Caulimovirus
Borates

Keywords

  • Arabidopsis thaliana
  • Boron
  • Membrane trafficking
  • Tolerance
  • Transporter

ASJC Scopus subject areas

  • Developmental Biology
  • Cell Biology

Cite this

Tolerance to excess-boron conditions acquired by stabilization of a BOR1 variant with weak polarity in Arabidopsis. / Wakuta, Shinji; Fujikawa, Teppei; Naito, Satoshi; Takano, Junpei.

In: Frontiers in Cell and Developmental Biology, Vol. 4, No. FEB, 4, 03.02.2016.

Research output: Contribution to journalArticle

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