College of Landscape Architecture, Beijing University of Agriculture, Beijing, China.
Beijing Collaborative Innovation Center for Eco-environmental Improvement with Forestry and Fruit Trees, Beijing, China.
Plant Biol (Stuttg). 2019 Mar;21(2):343-351. doi: 10.1111/plb.12941. Epub 2018 Dec 19.
Boron (B) is essential for normal plant growth, including pollen tube growth. B deficiency influences various physiological and metabolic processes in plants. However, the underlying mechanism of B deficiency in pollen tube growth is not sufficiently understood. In the present research, the influence of B deficiency on apple (Malus domestica) pollen tube growth was studied and the possible regulatory mechanism evaluated. Apple pollen grains were cultured under different concentrations of B. Scanning ion-selective electrode technique, fluorescence labelling and Fourier-transform infrared (FTIR) analysis were used to detect calcium ion flux, cytosolic Ca concentration ([Ca ]cyt), actin filaments and cell wall components of pollen tubes. B deficiency inhibited apple pollen germination and induced retardation of tube growth. B deficiency increased extracellular Ca influx and thus led to increased [Ca ]cyt in the pollen tube tip. In addition, B deficiency modified actin filament arrangement at the pollen tube apex. B deficiency also altered the deposition of pollen tube wall components. Clear differences were not observed in the distribution patterns of cellulose and callose between control and B deficiency treated pollen tubes. However, B deficiency affected distribution patterns of pectin and arabinogalactan proteins (AGP). Clear ring-like signals of pectins and AGP on control pollen tubes varied according to B deficiency. B deficiency further decreased acid pectins, esterified pectins and AGP content at the tip of the pollen tube, which were supported by changes in chemical composition of the tube walls. B appears to have an active role in pollen tube growth by affecting [Ca ]cyt, actin filament assembly and pectin and AGP deposition in the pollen tube. These findings provide valuable information that enhances our current understanding of the mechanism regulating pollen tube growth.
硼（B）是植物正常生长所必需的，包括花粉管生长。B 缺乏会影响植物的各种生理和代谢过程。然而，B 缺乏对花粉管生长的影响的潜在机制尚不完全清楚。本研究探讨了 B 缺乏对苹果（Malus domestica）花粉管生长的影响，并评估了可能的调控机制。将苹果花粉在不同浓度的 B 下培养。采用扫描离子选择性电极技术、荧光标记和傅里叶变换红外（FTIR）分析检测花粉管中钙离子流、细胞质 Ca 浓度([Ca ]cyt)、肌动蛋白丝和细胞壁成分。B 缺乏抑制苹果花粉萌发并诱导花粉管生长延迟。B 缺乏增加了细胞外 Ca 内流，从而导致花粉管尖端的 [Ca ]cyt 增加。此外，B 缺乏改变了花粉管顶端肌动蛋白丝的排列。B 缺乏还改变了花粉管壁成分的沉积。在对照和 B 缺乏处理的花粉管之间，纤维素和胼胝质的分布模式没有明显差异。然而，B 缺乏影响了果胶和阿拉伯半乳聚糖蛋白（AGP）的分布模式。果胶和 AGP 在对照花粉管上的清晰环状信号根据 B 缺乏而变化。B 缺乏进一步降低了花粉管尖端酸性果胶、酯化果胶和 AGP 的含量，这得到了管壁化学成分变化的支持。B 通过影响花粉管中的 [Ca ]cyt、肌动蛋白丝组装以及果胶和 AGP 的沉积，在花粉管生长中发挥积极作用。这些发现提供了有价值的信息，增强了我们对调节花粉管生长机制的理解。
