Departamento de Biología, Universidad Autónoma de Madrid, c/Darwin 2, Campus de Cantoblanco, 28049, Madrid, Spain.
BMC Plant Biol. 2020 Dec 9;20(1):552. doi: 10.1186/s12870-020-02750-4.
Legumes comprise important crops that offer major agronomic benefits, including the capacity of establishing symbiosis with rhizobia, fixing atmospheric N. It has been proven that legumes are particularly susceptible to boron (B) stress, which leads to important yield penalties. Boron (B) deficiency or toxicity in plants causes the inhibition of growth and an altered development. Under such conditions, the participation of two distinct protein families (the major intrinsic protein family MIP and the Boron transporter family BOR) is required to minimize detrimental effects caused by B stress. However, in legumes, little is known about the transport mechanisms responsible for B uptake and distribution, especially under deficiency.
A Medicago truncatula protein, MtNIP5;1 (Medtr1g097840) (homologous to the Arabidopsis thaliana AtNIP5;1) was identified as a novel legume B transporter involved in B uptake under deficiency. Further analyses revealed that this M. truncatula aquaporin expression was boron-regulated in roots, being induced under deficiency and repressed under toxicity. It localizes at the plasma membrane of root epidermal cells and in nodules, where B plays pivotal roles in symbiosis. Furthermore, the partial complementation of the nip5;1-1 A. thaliana mutant phenotype under B deficiency supports a functional role of MtNIP5;1 as a B transporter in this legume model plant.
The results here presented support a functional role of MtNIP5;1 in B uptake under deficiency and provides new insights into B transport mechanisms in legume species.
豆类作物是重要的农作物，具有重要的农业效益，包括与根瘤菌共生固氮的能力。已证明豆类作物特别容易受到硼（B）胁迫的影响，这会导致重要的产量损失。植物中的硼（B）缺乏或毒性会导致生长受到抑制和发育改变。在这种情况下，需要两种不同的蛋白质家族（主要内在蛋白家族 MIP 和硼转运蛋白家族 BOR）的参与，以最大限度地减少 B 胁迫造成的有害影响。然而，在豆类作物中，对于负责 B 吸收和分布的运输机制知之甚少，特别是在缺乏时。
鉴定了一种拟南芥 AtNIP5;1 同源物的 Medicago truncatula 蛋白 MtNIP5;1（Medtr1g097840），作为一种新的参与 B 缺乏时 B 吸收的豆类 B 转运蛋白。进一步的分析表明，这种拟南芥 aquaporin 的表达在根中受到硼的调节，在缺乏时诱导，在毒性时抑制。它定位于根表皮细胞的质膜和根瘤中，B 在共生中起着关键作用。此外，nip5;1-1 拟南芥突变体在 B 缺乏下的部分互补支持了 MtNIP5;1 作为 B 转运蛋白在这种豆科模式植物中的功能作用。
这里提出的结果支持 MtNIP5;1 在 B 缺乏下的 B 吸收中的功能作用，并为豆科物种的 B 运输机制提供了新的见解。
