Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721-0106, USA.
Cytoskeleton (Hoboken). 2011 Aug;68(8):459-69. doi: 10.1002/cm.20524. Epub 2011 Aug 23.
The characteristic geometry of the unicellular chlorophyte Chlamydomonas reinhardtii has contributed to its adoption as a model system for cellular asymmetry and organelle positioning. The eyespot, a photosensitive organelle, is localized asymmetrically in the cell at a precisely defined position relative to the flagella and cytoskeletal microtubule rootlets. We have isolated a mutant, named pey1 for posterior eyespot, with variable microtubule rootlet lengths. The length of the acetylated daughter four-membered (D4) microtubule rootlet correlates with the position of the eyespot, which appears in a posterior position in the majority of cells. The correlation of rootlet length with eyespot positioning was also observed in the cmu1 mutant, which has longer acetylated microtubules, and the mlt1 mutant, in which the rootlet microtubules are shorter. Observation of eyespot positioning after depolymerization of rootlet microtubules indicated that eyespot position is fixed early in eyespot development and becomes independent of the rootlet. Our data demonstrate that the length of the D4 rootlet is the major determinant of eyespot positioning on the anterior-posterior axis and are suggestive that the gene product of the PEY1 locus is a novel regulator of acetylated microtubule length.
单细胞绿藻衣藻的特征几何形状使其成为细胞不对称和细胞器定位的模型系统。眼点是一种感光细胞器，在细胞中相对于鞭毛和细胞骨架微管根鞘呈不对称定位。我们分离到一个突变体，命名为 pey1（意为后眼点），其微管根鞘长度可变。乙酰化的四联体（D4）微管根鞘的长度与眼点的位置相关，在大多数细胞中，眼点位于后位。cmu1 突变体（其乙酰化微管较长）和 mlt1 突变体（其根鞘微管较短）中也观察到了根鞘长度与眼点定位的相关性。在根鞘微管解聚后观察眼点定位，表明眼点的位置在眼点发育的早期就已固定，并且与根鞘无关。我们的数据表明，D4 根鞘的长度是眼点在前-后轴上定位的主要决定因素，并且表明 PEY1 基因座的产物是乙酰化微管长度的新型调节因子。
