Genetic variation of BnaA3.NIP5;1 expressing in the lateral root cap contributes to boron deficiency tolerance in Brassica napus.

Mingliang He,Jinyao Zhang,Shaowu Xue,Shou Qiu,Sheliang Wang,Cheng Zhang,Lei Shi,Fangsen Xu,Liu Liu,Hong Wang,Guangsheng Yang,Zhixi Tian

doi:10.1371/journal.pgen.1009661

Mingliang He, Jinyao Zhang + Show 10 more

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https://doi.org/10.1371/journal.pgen.1009661

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Abstract

Boron (B) is essential for vascular plants. Rapeseed (Brassica napus) is the second leading crop source for vegetable oil worldwide, but its production is critically dependent on B supplies. BnaA3.NIP5;1 was identified as a B-efficient candidate gene in B. napus in our previous QTL fine mapping. However, the molecular mechanism through which this gene improves low-B tolerance remains elusive. Here, we report genetic variation in BnaA3.NIP5;1 gene, which encodes a boric acid channel, is a key determinant of low-B tolerance in B. napus. Transgenic lines with increased BnaA3.NIP5;1 expression exhibited improved low-B tolerance in both the seedling and maturity stages. BnaA3.NIP5;1 is preferentially polar-localized in the distal plasma membrane of lateral root cap (LRC) cells and transports B into the root tips to promote root growth under B-deficiency conditions. Further analysis revealed that a CTTTC tandem repeat in the 5'UTR of BnaA3.NIP5;1 altered the expression level of the gene, which is tightly associated with plant growth and seed yield. Field tests with natural populations and near-isogenic lines (NILs) confirmed that the varieties carried BnaA3.NIP5;1Q allele significantly improved seed yield. Taken together, our results provide novel insights into the low-B tolerance of B. napus, and the elite allele of BnaA3.NIP5;1 could serve as a direct target for breeding low-B-tolerant cultivars.

Highlights

Boron (B) is an essential micronutrient for all higher plants
Our results demonstrate that BnaA3.NOD26-LIKE MAJOR INTRINSIC PROTEIN5;1 (NIP5);1 is preferentially located in the distal side plasma membrane of lateral root cap (LRC) cells and transports B into meristem zone to promote root growth under B limitation, which provide insights into the LRC’s function in mineral nutrition
Consistent with the results of the 10B accumulation assay in the root tip, the results showed that Qingyou 10 (QY10) and NILQ-Westar 10 (W10) had higher B concentrations in the root tips than did W10 at 0.1 μM B, especially in the cells in meristem region (Fig 3E); there was no distinct difference under 100 μM B (Fig 3F)

Summary

Introduction

Boron (B) is an essential micronutrient for all higher plants. The natural abundance of B is relatively low in the soil [1], and B is very leachable, especially in areas of high rainfall (South-East Asia, Brazil, China). The leaching of B from soil leads to a decrease in the availability of B to plants. B deficiency is a worldwide agricultural production problem that has been reported in the field for at least 132 crops from 80 countries [2]. B deficiency during early vegetative stages leads to slow growth and low biomass, whereas B deficiency can considerably diminish productivity [7]. Application of B fertilizer can alleviate B-deficiency problems, but borate rock is a non-renewable mineral resource. Genetic improvement of B efficiency of crops is a promising and cost-efficient strategy in B-deficient regions

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