Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín (CSIC), Profesor Albareda nº 1, 18008 Granada, Spain.
Int J Mol Sci. 2020 Mar 4;21(5):1748. doi: 10.3390/ijms21051748.
Boron (B) is an essential micronutrient for higher plants, having structural roles in primary cell walls, but also other functions in cell division, membrane integrity, pollen germination or metabolism. Both high and low B levels negatively impact crop performance. Thus, plants need to maintain B concentration in their tissues within a narrow range by regulating transport processes. Both active transport and protein-facilitated diffusion through aquaporins have been demonstrated. This study aimed at elucidating the possible involvement of some plant aquaporins, which can potentially transport B and are regulated by the arbuscular mycorrhizal (AM) symbiosis in the plant B homeostasis. Thus, AM and non-AM plants were cultivated under 0, 25 or 100 μM B in the growing medium and subjected or not subjected to drought stress. The accumulation of B in plant tissues and the regulation of plant aquaporins and other B transporters were analyzed. The benefits of AM inoculation on plant growth (especially under drought stress) were similar under the three B concentrations assayed. The tissue B accumulation increased with B availability in the growing medium, especially under drought stress conditions. Several maize aquaporins were regulated under low or high B concentrations, mainly in non-AM plants. However, the general down-regulation of aquaporins and B transporters in AM plants suggests that, when the mycorrhizal fungus is present, other mechanisms contribute to B homeostasis, probably related to the enhancement of water transport, which would concomitantly increase the passive transport of this micronutrient.
硼（B）是高等植物的必需微量元素，在初生细胞壁中具有结构作用，但在细胞分裂、膜完整性、花粉萌发或代谢中也具有其他功能。高浓度和低浓度的硼都会对作物的表现产生负面影响。因此，植物需要通过调节运输过程将组织内的硼浓度维持在狭窄的范围内。已经证明了主动运输和通过水通道蛋白的蛋白促进扩散。本研究旨在阐明一些植物水通道蛋白的可能参与，这些水通道蛋白可以潜在地运输硼，并受丛枝菌根（AM）共生体在植物硼稳态中的调节。因此，在生长介质中培养 AM 和非 AM 植物，在 0、25 或 100 μM B 下，并进行或不进行干旱胁迫。分析植物组织中硼的积累和植物水通道蛋白和其他硼转运蛋白的调节。在三种测定的硼浓度下，AM 接种对植物生长（尤其是在干旱胁迫下）的益处相似。组织硼积累随生长介质中硼的可用性增加而增加，特别是在干旱胁迫条件下。几种玉米水通道蛋白在低或高硼浓度下受到调节，主要在非 AM 植物中。然而，AM 植物中水通道蛋白和硼转运蛋白的普遍下调表明，当存在菌根真菌时，其他机制有助于硼稳态，可能与增强水运输有关，这将同时增加这种微量元素的被动运输。
