Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Biochem Biophys Res Commun. 2010 Jan 1;391(1):868-73. doi: 10.1016/j.bbrc.2009.11.154. Epub 2009 Nov 27.
Filamentous ascomycetes form hyphal networks that are compartmentalized by septa which have a perforated pore allowing the passage of cytoplasm and organelles between adjacent hyphal compartments. Thus, the septal pore may play an important role in the organized growth of multicellular organisms. Upon hyphal injury, the septal pore is plugged by a wound-healing organelle, known as the Woronin body, to prevent excessive cytoplasmic leakage. However, the movement of proteins towards the septal pore in response to stress has not been extensively studied in filamentous fungi. In this study, we identified an Aspergillus oryzae protein, AoSO, which is homologous to the Neurospora crassa SO protein that was reported to accumulate at the septal pore in aging hyphae. The DeltaAoso strain showed excessive cytoplasmic leakage upon hyphal injury similar to the Woronin body-deficient strain DeltaAohex1. Cellular localization studies using EGFP showed that AoSO accumulated at the septal pore adjacent to the injured compartment, while it was dispersed throughout the cytoplasm under normal growth conditions. These results indicate that AoSO plays a role in preventing excessive cytoplasmic leakage upon hyphal injury by accumulating at the septal pore. Furthermore, AoSO accumulated at the septal pore in response to various stresses, including low and high temperature, extreme acidic and alkaline pH, and nitrogen and carbon depletion. Physical stress induced by pulse laser treatment on a hyphal region at a distance from the septum caused accumulation of the AoSO protein at the septal pore within only a few minutes. This study presents a novel behavior in which a filamentous fungal protein relocalizes to the septal pore in response to various stresses.
丝状子囊菌形成菌丝网络，这些网络被隔膜分隔，隔膜上有一个穿孔的孔，允许细胞质和细胞器在相邻的菌丝隔室之间通过。因此，隔膜孔可能在多细胞生物的有组织生长中发挥重要作用。在菌丝受伤时，隔膜孔被称为沃罗宁体的创伤愈合细胞器堵塞，以防止细胞质过度泄漏。然而，在丝状真菌中，蛋白质在应对应激时向隔膜孔的移动尚未得到广泛研究。在这项研究中，我们鉴定了一种 Aspergillus oryzae 蛋白 AoSO，它与 Neurospora crassa 的 SO 蛋白同源，据报道，该蛋白在老化菌丝的隔膜孔处积累。DeltaAoso 菌株在菌丝受伤时表现出过度的细胞质泄漏，类似于沃罗宁体缺陷菌株 DeltaAohex1。使用 EGFP 的细胞定位研究表明，AoSO 在与受伤隔室相邻的隔膜孔处积累，而在正常生长条件下，它分散在细胞质中。这些结果表明，AoSO 通过在隔膜孔处积累来防止菌丝受伤时的细胞质过度泄漏。此外，AoSO 在各种应激下，包括低温和高温、极端酸碱 pH 值以及氮和碳耗尽时，都在隔膜孔处积累。对远离隔膜的菌丝区域进行脉冲激光处理引起的物理应激仅在几分钟内就导致 AoSO 蛋白在隔膜孔处积累。这项研究提出了一种新的行为，即丝状真菌蛋白在应对各种应激时重新定位到隔膜孔。
