Durbak Amanda R, Phillips Kimberly A, Pike Sharon, O'Neill Malcolm A, Mares Jonathan, Gallavotti Andrea, Malcomber Simon T, Gassmann Walter, McSteen Paula
Division of Biological Sciences, Bond Life Sciences Center, Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri 65211.
Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802.
Plant Cell. 2014 Jul;26(7):2978-95. doi: 10.1105/tpc.114.125898. Epub 2014 Jul 17.
The element boron (B) is an essential plant micronutrient, and B deficiency results in significant crop losses worldwide. The maize (Zea mays) tassel-less1 (tls1) mutant has defects in vegetative and inflorescence development, comparable to the effects of B deficiency. Positional cloning revealed that tls1 encodes a protein in the aquaporin family co-orthologous to known B channel proteins in other species. Transport assays show that the TLS1 protein facilitates the movement of B and water into Xenopus laevis oocytes. B content is reduced in tls1 mutants, and application of B rescues the mutant phenotype, indicating that the TLS1 protein facilitates the movement of B in planta. B is required to cross-link the pectic polysaccharide rhamnogalacturonan II (RG-II) in the cell wall, and the percentage of RG-II dimers is reduced in tls1 inflorescences, indicating that the defects may result from altered cell wall properties. Plants heterozygous for both tls1 and rotten ear (rte), the proposed B efflux transporter, exhibit a dosage-dependent defect in inflorescence development under B-limited conditions, indicating that both TLS1 and RTE function in the same biological processes. Together, our data provide evidence that TLS1 is a B transport facilitator in maize, highlighting the importance of B homeostasis in meristem function.
硼元素（B）是植物必需的微量营养元素，缺硼会导致全球范围内农作物严重减产。玉米（Zea mays）无雄穗1（tls1）突变体在营养生长和花序发育方面存在缺陷，这与缺硼的影响类似。图位克隆表明，tls1编码一种水通道蛋白家族中的蛋白质，与其他物种中已知的硼通道蛋白是共直系同源物。转运试验表明，TLS1蛋白促进硼和水进入非洲爪蟾卵母细胞。tls1突变体中的硼含量降低，施用硼可挽救突变体表型，这表明TLS1蛋白促进硼在植物体内的转运。硼是细胞壁中果胶多糖鼠李半乳糖醛酸聚糖II（RG-II）交联所必需的，tls1花序中RG-II二聚体的百分比降低，表明这些缺陷可能是由细胞壁特性改变所致。同时携带tls1和拟硼外流转运体“烂穗”（rte）的杂合植株在硼限制条件下花序发育呈现剂量依赖性缺陷，这表明TLS1和RTE在相同的生物学过程中发挥作用。我们的数据共同证明TLS1是玉米中的硼转运促进因子，突出了硼稳态在分生组织功能中的重要性。
