Cheung Alice Y, Wu Hen-Ming
Department of Biochemistry and Molecular Biology, University of Massachusetts, Lederle Graduate Research Tower, Amherst, MA 01003, USA.
J Exp Bot. 2007;58(1):75-82. doi: 10.1093/jxb/erl122. Epub 2006 Sep 15.
Eukaryotic cellular functions are achieved by concerted activities in the cytosol and functions compartmentalized in the nucleus and other membrane-bound organelles. Moreover, the cytosol and nucleoplasm are populated with mega molecular ensembles that are specialized for different metabolic and biochemical processes. Pollen tubes are unique plant cells with a dramatic growth polarity. Tube growth is restricted to the tip and is supported by a polarized cytoplasmic organization. The apical region of elongating pollen tubes is a domain occupied exclusively by transport vesicles to support the secretion and endocytic activity needed for the rapid cell expansion at the apex. Larger organelles are predominantly segregated to the cytoplasm distal to the subapical region. Underlying the organelle compartmentalization is an elaborate actin cytoskeleton with distinct structural and dynamics properties at the tip, in the subapical region, and in the cytoplasm subtending it. Cytoplasmic domains with differential ionic conditions and spatially restricted localization of molecules in pollen tubes may also be important for regulating the polar cell growth process. The polarized cellular organization in pollen tubes drives an extremely efficient cell growth process that is responsive to extracellular signals, including directional cues. It may be an amplified framework of the cytoplasmic architecture that supports growth in other plant cell types that involves considerably more subtle and transient differential cell expansion.
真核细胞的功能是通过细胞质溶胶中的协同活动以及细胞核和其他膜结合细胞器中分隔的功能来实现的。此外，细胞质溶胶和核质中充满了专门用于不同代谢和生化过程的大分子聚集体。花粉管是具有显著生长极性的独特植物细胞。管的生长仅限于顶端，并由极化的细胞质组织支持。伸长的花粉管的顶端区域是一个仅由运输小泡占据的区域，以支持顶端快速细胞扩张所需的分泌和内吞活动。较大的细胞器主要被分隔到顶端区域远端的细胞质中。细胞器的区室化之下是一个精细的肌动蛋白细胞骨架，在顶端、顶端区域下方以及其下方的细胞质中具有不同的结构和动力学特性。花粉管中具有不同离子条件和分子空间受限定位的细胞质区域对于调节极性细胞生长过程也可能很重要。花粉管中的极化细胞组织驱动了一个极其高效的细胞生长过程，该过程对包括定向线索在内的细胞外信号作出反应。它可能是细胞质结构的一个放大框架，支持其他植物细胞类型中的生长，这些细胞类型涉及更为微妙和短暂的差异细胞扩张。
