胞间连丝与大分子物质的胞间转移

PLASMODESMATA AND INTERCELLULAR TRAFFI CKING OF MACROMOLECULES

胞间连丝是细胞间细胞器，是细胞间通讯的直接途径。一般认为，胞间连丝允许通过物质的分子量上限（ＳＥＬ）是８００～１０００Ｄａ．近年来研究的许多证据表明，胞间连丝的ＳＥＬ随组织种类及其生理状况而异。在某些情况下，它可以允许大分子物质通过，如病毒运动蛋白与胞间连丝相互作用，使病毒通过胞间连丝转移。玉米突变体ｋｎ１基因异常表达的ＫＮ１可使包括表皮在内的各层组织结瘤，ＫＮ１是细胞间移动的信息物，Ｐ蛋白可由伴胞通过胞间连丝转移到筛管。某些组织中胞间连丝很高的ＳＥＬ和发育过程胞间连丝ＳＥＬ的变化可能在植物发育调控中有重要作用。本文对大分子通过胞间连丝转移的机理进行了讨论。

Plasmodesmata are supracellular organelles connecting two adjacent plant cells, providing a pathway of direct intercellular communication. It is generally accepted that the size exclusion limit (SEL) of plasmodesmata is about 800～1000 Da. There are many evidences indicating that plasmodesmata SEL varies in different tissues under different physiological conditions. Under certain circumstances plasmodesmata SEL could be very high and macromolecules could traffic through plasmodesmata. Interaction with plasmodesmata, virus movement protein (MP) could modify SEL of plasmodesmata and enable virus transfer from cell to cell. In maize mutant kn1, the protein KN1 might be signal molecule which results in the formation of tumors in epidermis and other tissues. P protein could move from companian cell to sieve tube through plasmodesmata. The high plasmodesmal SEL in some tissues and the change of plasmodesmal SEL during development might play an important role in the regulation of development. The mechanisms of intercellular trafficking of macromolecules via plasmodesmata are discussed.