Grolig F, Moch J, Schneider A, Galland P
Fachbereich Biologie, Philipps-Universität Marburg, Marburg, Germany.
Plant Biol (Stuttg). 2014 Jan;16 Suppl 1:167-78. doi: 10.1111/plb.12065. Epub 2013 Aug 8.
Growth, photo- and gravitropism of sporangiophores of the zygomycete Phycomyces blakesleeanus occur within the apical growing zone, a cylindrical structure (diameter about 100 μm) that reaches about 1.5-2.5 mm below the tip and has growth rates up to 50 μm·min(-1) . To better understand morphogenesis and growth of the giant aerial hypha, we investigated with confocal microscopy and inhibitors the actin cytoskeleton and by in-vivo particle tracking the associated organelle movement. We found stage-1 sporangiophores (without sporangium) possess an actin cytoskeleton with polar zonation. (i) In the apex, abundant microfilaments without preferential orientation entangled numerous nuclei as well as a conspicious complex of some 200 lipid globules. Microfilament patches (≈ 1.6-μm diameter) are clustered in the tip and were found in the apical cortex, whereas short, curved microfilament bundles (≈ 2.3-μm long) prevailed in the subapex. (ii) In a transition zone downwards to the shaft, the microfilaments rearranged into a dense mat of longitudinal microfilaments that was parallel close to the periphery but more random towards the cell centre. Numerous microfilament patches were found near the cortex (≈ 10/100 μm(2) ); their number decreased rapidly in the subcortex. In contrast, the short, curved microfilament bundles were found only in the subcortex. (iii) The basal shaft segment of the sporangiophore (with central vacuole) exhibited bidirectional particle movement over long distances (velocity ≈ 2 μm·s(-1) ) along massive longitudinal, subcortical microfilament cables. The zonation of the cytoskeleton density correlated well with the local growth rates at the tip of the sporangiophore, and appears thus as a structural prerequisite for growth and bending.
接合菌黑根霉的孢子囊柄的生长、向光性和向地性发生在顶端生长区，这是一个圆柱形结构（直径约100μm），延伸至顶端下方约1.5 - 2.5mm处，生长速率可达50μm·min⁻¹。为了更好地理解巨型气生菌丝的形态发生和生长，我们使用共聚焦显微镜和抑制剂研究了肌动蛋白细胞骨架，并通过体内粒子追踪研究了相关细胞器的运动。我们发现1期孢子囊柄（无孢子囊）具有极性分区的肌动蛋白细胞骨架。（i）在顶端，大量无优先取向的微丝缠绕着众多细胞核以及约200个脂质球组成的明显复合体。微丝斑块（直径约1.6μm）聚集在顶端，并在顶端皮层中发现，而短的、弯曲的微丝束（约2.3μm长）在亚顶端占主导。（ii）在向下至柄部的过渡区，微丝重新排列成纵向微丝的致密层，在靠近周边处平行，但向细胞中心方向更随机。在皮层附近发现大量微丝斑块（约10/100μm²）；它们的数量在皮层下迅速减少。相比之下，短的、弯曲的微丝束仅在皮层下发现。（iii）孢子囊柄的基部柄段（有中央液泡）沿着大量纵向的皮层下微丝束表现出长距离的双向粒子运动（速度约2μm·s⁻¹）。细胞骨架密度的分区与孢子囊柄顶端的局部生长速率密切相关，因此似乎是生长和弯曲的结构先决条件。
