Departamento de Microbiología, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, Mexico.
School of Life Sciences, Arizona State University, Tempe, AZ, USA.
Fungal Genet Biol. 2019 Apr;125:13-27. doi: 10.1016/j.fgb.2018.11.008. Epub 2019 Jan 4.
In filamentous fungi, polarized growth is the result of vesicle secretion at the hyphal apex. Motor proteins mediate vesicle transport to target destinations on the plasma membrane via actin and microtubule cytoskeletons. Myosins are motor proteins associated with actin filaments. Specifically, class V myosins are responsible for cargo transport in eukaryotes. We studied the dynamics and localization of myosin V in wild type hyphae of Neurospora crassa and in hyphae that lacked MYO-5. In wild type hyphae, MYO-5-GFP was localized concentrated in the hyphal apex and colocalized with Spitzenkörper. Photobleaching studies showed that MYO-5-GFP was transported to the apex from subapical hyphal regions. The deletion of the class V myosin resulted in a reduced rate of hyphal growth, apical hyperbranching, and intermittent loss of hyphal polarity. MYO-5 did not participate in breaking the symmetrical growth during germination but contributed in the apical organization upon establishment of polarized growth. In the Δmyo-5 mutant, actin was organized into thick cables in the apical and subapical hyphal regions, and the number of endocytic patches was reduced. The microvesicles-chitosomes observed with CHS-1-GFP were distributed as a cloud occupying the apical dome and not in the Spitzenkörper as the WT strain. The mitochondrial movement was not associated with MYO-5, but tubular vacuole position is MYO-5-dependent. These results suggest that MYO-5 plays a role in maintaining apical organization and the integrity of the Spitzenkörper and is required for normal hyphal growth, polarity, septation, conidiation, and proper conidial germination.
在丝状真菌中，极化生长是菌丝顶端囊泡分泌的结果。马达蛋白通过肌动蛋白和微管细胞骨架将囊泡运输到质膜上的靶标位置。肌球蛋白是与肌动蛋白丝相关的马达蛋白。具体来说，V 类肌球蛋白负责真核生物的货物运输。我们研究了肌球蛋白 V 在粗糙脉孢菌野生型菌丝和缺乏 MYO-5 的菌丝中的动态和定位。在野生型菌丝中，MYO-5-GFP 集中定位于菌丝顶端，并与 Spitzenkörper 共定位。光漂白研究表明，MYO-5-GFP 从亚顶端菌丝区域被运输到顶端。V 类肌球蛋白的缺失导致菌丝生长速度降低、顶端过度分枝和菌丝极性间歇性丧失。MYO-5 不参与萌发过程中的对称生长，但在建立极化生长时有助于顶端组织。在Δmyo-5 突变体中，肌动蛋白在顶端和亚顶端菌丝区域被组织成厚的电缆，内吞斑的数量减少。用 CHS-1-GFP 观察到的微囊泡-几丁质体被分布在占据顶端穹顶的云状物中，而不是 WT 菌株中的 Spitzenkörper 中。线粒体的运动与 MYO-5 无关，但管状液泡的位置是依赖于 MYO-5 的。这些结果表明，MYO-5 在维持顶端组织和 Spitzenkörper 的完整性方面发挥作用，并且是正常菌丝生长、极性、分隔、产孢和适当的分生孢子萌发所必需的。
