CAJ | 학술논문

胞间连丝作为一种细胞质结构将相邻的细胞连系起来而形成植物的共质体。胞间连丝通过调控许多离子和分子的共质体运输而广泛地参与植物的生命活动。胞间连丝的主要构成部分是细胞质膜、连丝小管、以及位于二者之间的环层细胞质。这三者都很容易在电子显微镜下观察到。细胞骨架的成分(肌动蛋白和肌球蛋白)起到稳定胞间连丝的作用。同时，钙结合蛋白可能具有调节胞间连丝功能的作用。在胞间连丝里，环层细胞质为大多数溶质提供共质体运输的通道，而有些物质的共质体运输则可能是通过连丝小管的内腔、连丝小管的壳层、甚或是细胞质膜来实现的。共质体可以细分为数个区块，它们各自允许不同大小的分子(从低于1000到高于10000道尔顿)通过。从发生上看，胞间连丝可以是初生的，也可以是次生的。前者是伴随着新细胞壁的形成而产生的，而后者则是在已有的细胞壁上产生的。胞间连丝的动态性质还表现在它们的频率是处于变化之中的，这是由组织或植物整体的发育和生理状态决定的。虽然共质体运输的基本形式是扩散，但胞间连丝对于某些离子和分子却是有选择性的。在病毒感染细胞时，病毒的移动蛋白作用于胞间连丝的受体蛋白，结果，胞间连丝被显著地扩张(其机理尚不清楚)。于是，病毒的移动蛋白连同与之结合在一起的病毒基因组进入毗邻的健康细胞。一些植物源性的蛋白质也能够通过胞间连丝来运输；推测其方式类似于病毒的移动蛋白。有些植物蛋白质本身就是信号分子，它们调节分化和其他活动。与此相反，还有一些植物蛋白质的共质体运输却并不是通过特异的方式来实现的。
포간련사작위일충세포질결구장상린적세포련계기래이형성식물적공질체。포간련사통과조공허다리자화분자적공질체운수이엄범지삼여식물적생명활동。포간련사적주요구성부분시세포질막、련사소관、이급위우이자지간적배층세포질。저삼자도흔용역재전자현미경하관찰도。세포골가적성분(기동단백화기구단백)기도은정포간련사적작용。동시，개결합단백가능구유조절포간련사공능적작용。재포간련사리，배층세포질위대다수용질제공공질체운수적통도，이유사물질적공질체운수칙가능시통과련사소관적내강、련사소관적각층、심혹시세포질막래실현적。공질체가이세분위수개구괴，타문각자윤허불동대소적분자(종저우1000도고우10000도이돈)통과。종발생상간，포간련사가이시초생적，야가이시차생적。전자시반수착신세포벽적형성이산생적，이후자칙시재이유적세포벽상산생적。포간련사적동태성질환표현재타문적빈솔시처우변화지중적，저시유조직혹식물정체적발육화생리상태결정적。수연공질체운수적기본형식시확산，단포간련사대우모사리자화분자각시유선택성적。재병독감염세포시，병독적이동단백작용우포간련사적수체단백，결과，포간련사피현저지확장(기궤리상불청초)。우시，병독적이동단백련동여지결합재일기적병독기인조진입비린적건강세포。일사식물원성적단백질야능구통과포간련사래운수；추측기방식유사우병독적이동단백。유사식물단백질본신취시신호분자，타문조절분화화기타활동。여차상반，환유일사식물단백질적공질체운수각병불시통과특이적방식래실현적。
Plasmodesmata (PDs) are cytoplasmic structures that link adjacentcells to form the symplast of a plant. PDs are involved extensively in a plant's life by mediating symplastic transport of a wide range of ions and molecules. Major components of a plasmodesma (PD) include a plasma membrane, a desmotubule, and a cytoplasmic annulus, all of which are readily detectable by electron microscopy. Both the plasma membrane and the desmotubule contain proteinaceous particles, thought to be involved in altering the size of the cytoplasmic annulus. Cytoskeleton elements (actin and myosin) are essential for maintaining the integrity of PDs. Together with these elements, calcium-binding proteins probably play a significant role in regulating PD function. Symplastic transport occurs through the cytoplasmic annulus for the great majority of solutes, while other substances may traverse through the desmotubule internal compartment, the desmotubule shell, or the plasma membrane. The symplast is subdivided into several domains with varying molecular size exclusion limits (ranging from <1 kD to >10 kD). Plasmodesmata can be either primary or secondary; the former are developed during new wall formation and the latter are made in existing walls. The dynamic nature of plasmodesmata is also reflected by their changing frequencies, which, in turn, depend on the developmental and physiological status of the tissue or the entire plant. While diffusion is the major mechanism of symplastic transport, plasmodesmata are selective for certain ions and molecules. Upon viral infection, viral movement proteins interact with PD receptor proteins and, as a result of yet unknown mechanisms, the plasmodesmata are remarkably dilated to allow viral movement proteins and the bound viral genome to enter healthy cells. Some proteins of plant origin are also able to traverse plasmodesmata, presumably in ways similar to viral movement proteins. Some of these plant proteins are probably signal molecules contributing to cell differentiation and other activities. Other proteins move cell-to-cell in a non-specific manner.