biologia plantarum

Biologia plantarum 2018, 62:121-128 | DOI: 10.1007/s10535-017-0744-5

The effect of boron availability, CO₂, and irradiance on relative accumulation of the major boron transport proteins, BOR1 and NIP5;1

S. Mishra^1,*, S. A. Heckathorn¹, J. M. Frantz², C. Krause²

¹ Department of Environmental Sciences, University of Toledo, Toledo, USA

² United States Department of Agriculture, Agricultural Research Service, University of Toledo, Toledo, USA

Boron (B) is an essential plant micronutrient. Two major B-transport proteins have been recently identified and partially characterized: BOR1, a high-affinity B efflux transporter involved in xylem loading, and NIP5;1, a plasma-membrane boric-acid channel involved in B uptake. To date, studies of these B transporters have investigated their expression individually (mainly as mRNA), and only in response to variation in B availability (mostly B deficiency); the influence of other factors, such as plant resource status, has not been studied. To address this, we grew geranium (Pelargonium × hortorum cv. Maverick White) plants under ambient or elevated CO₂ concentration, different sub-saturating irradiances, and different B availability. For comparison we also grew three other species (Arabidopsis thaliana, Azolla caroliniana, and Hordeum vulgare) under broad range of B supply. Relative accumulation of BOR1 and NIP5;1 proteins were measured using protein-specific antibodies and Western blotting or ELISA. Elevated CO₂ significantly increased content of NIP5;1, while increases in irradiance increased BOR1 content, but decreased NIP5;1 content. Across species, content of both transporters often decreased with increasing B availability, but sometimes remained unchanged or even increased, depending on CO₂, irradiance, species, or transporter. Content of BOR1 and NIP5;1 was correlated with root proteins, B content, and sugar content (for high CO₂ only), as well as B uptake, but CO₂ and irradiance often affected these relationships. Thus, relative accumulation of BOR1 and NIP5;1 is influenced not only by B content, as expected, but by other environmental factors as well.

Keywords: Arabidopsis thaliana; Azolla caroliniana; B uptake; Hordeum vulgare; Pelargonium × hortorum; photosynthesis

Subjects: boron; transport proteins; carbon dioxide concentration; irradiance

Species: Arabidopsis thaliana; Azolla caroliniana; Hordeum vulgare; Pelargonium x hortorum

Received: January 9, 2015; Revised: March 27, 2017; Accepted: March 28, 2017; Published: January 1, 2018Show citation