Nutrient deficiency in soil poses a widespread agricultural problem. Boron (B) is an essential micronutrient in plants, and its deficiency causes defects in both vegetative and reproductive growth in various crops in the field. In Arabidopsis thaliana, increased expression of a major borate transporter gene AtBOR1 or boric acid channel gene AtNIP5;1 improves plant growth under B-deficient conditions. In this study, we examined whether high expression of a borate transporter gene increases B accumulation in shoots and improves the growth of tomato plant, a model of fruit-bearing crops, under B-deficient conditions. We established three independent transgenic tomato plants lines expressing AtBOR1 using Agrobacterium-mediated transformation of tomato (Solanum lycopersicum L. cv. Micro-Tom). Reverse transcription-polymerase chain reaction (RT-PCR) analysis confirmed that two lines (Line 1 and Line 2) more strongly expressed AtBOR1than Line 3. Wild-type plants and the transgenic plants were grown hydroponically under B-sufficient and B-deficient conditions. Wild-type and Line 3 (weakly expressing transgenic line) showed a defect in shoot growth under B-deficient conditions, especially in the development of new leaves. However, seedlings of Line 1 and Line 2, the transgenic lines showing strong AtBOR1 expression, did not show the B-deficiency phenotype in newly developing leaves. In agreement with this phenotype, shoot biomass under low-B conditions was higher in the strongly expressing AtBOR1line. B concentrations in leaves or fruits were also higher in Line 2 and Line 1. The present study demonstrates that strong expression of AtBOR1 improved growth in tomato under B-deficient conditions.
Keywords: AtBOR1, boron-deficiency, nutrient, tomato, transgenic, transporter
Citation: Uraguchi S, Kato Y, Hanaoka H, Miwa K and Fujiwara T (2014) Generation of boron-deficiency-tolerant tomato by overexpressing an Arabidopsis thaliana borate transporter AtBOR1. Front. Plant Sci. 5:125. doi: 10.3389/fpls.2014.00125
Received: 05 December 2013; Accepted: 16 March 2014;
Published online: 01 April 2014.
Edited by:Felipe Klein Ricachenevsky, Universidade Federal do Rio Grande do Sul, Brazil
Reviewed by:Fangsen Xu, Huazhong Agricultural University, China
Copyright © 2014 Uraguchi, Kato, Hanaoka, Miwa and Fujiwara. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Toru Fujiwara, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan e-mail: firstname.lastname@example.org
†Present address: Shimpei Uraguchi, Department of Plant Physiology, University of Bayreuth, 95440 Bayreuth, Germany