College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang 110866, China.
Int J Mol Sci. 2024 Aug 16;25(16):8950. doi: 10.3390/ijms25168950.
Potassium (K) is an essential nutrient for the growth and development of plants. Root hairs are the main parts of plants that absorb K. The regulation of plant root hair growth in response to a wide range of environmental stresses is crucially associated with the dynamics of actin filaments, and the thick actin bundles at the apical and sub-apical regions are essential for terminating the rapid elongation of root hair cells. However, the dynamics and roles of actin filaments in root hair growth in plants' response to low K stress are not fully understood. Here, we revealed that root hairs grow faster and longer under low K stress than the control conditions. Compared to control conditions, the actin filaments in the sub-apex of fast-growing wild-type root hairs were longer and more parallel under low K stress, which correlates with an increased root hair growth rate under low K stress; the finer actin filaments in the sub-apex of the early fully grown Col-0 root hairs under low K stress, which is associated with low K stress-induced root hair growth time. Further, actin bundling protein Villin1 (VLN1) and Villin4 (VLN4) was inhibited and induced under low K stress, respectively. Low K stress-inhibited VLN1 led to decreased bundling rate and thick bundle formation in the early fully grown phase. Low K stress-induced VLN4 functioned in keeping long filaments in the fast-growing phase. Furthermore, the analysis of genetics pointed out the involvement of VLN1 and VLN4 in the growth of root hairs under the stress of low potassium levels in plants. Our results provide a basis for the dynamics of actin filaments and their molecular regulation mechanisms in root hair growth in response to low K stress.
钾（K）是植物生长和发育所必需的营养物质。根毛是植物吸收 K 的主要部位。植物根毛在应对广泛的环境胁迫时的生长调节与肌动蛋白丝的动力学密切相关，顶端和亚顶端区域的厚肌动蛋白束对于终止根毛细胞的快速伸长是必不可少的。然而，在植物应对低钾胁迫时，根毛生长中肌动蛋白丝的动力学和作用尚不完全清楚。在这里，我们揭示了在低钾胁迫下，根毛的生长速度比对照条件下更快、更长。与对照条件相比，在低钾胁迫下，快速生长的野生型根毛亚顶端的肌动蛋白丝更长且更平行，这与低钾胁迫下根毛生长速率的增加有关；在低钾胁迫下，早期完全生长的 Col-0 根毛亚顶端的较细肌动蛋白丝，与低钾胁迫诱导的根毛生长时间有关。此外，肌动蛋白束蛋白Villin1（VLN1）和Villin4（VLN4）分别在低钾胁迫下受到抑制和诱导。低钾胁迫抑制的 VLN1 导致早期完全生长阶段束的形成减少和束变厚。低钾胁迫诱导的 VLN4 功能在于在快速生长阶段保持长丝。此外，遗传学分析指出 VLN1 和 VLN4 参与了植物低钾胁迫下根毛的生长。我们的研究结果为低钾胁迫下根毛生长中肌动蛋白丝的动力学及其分子调控机制提供了依据。
