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식물의 관다발 시스템
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자연과학>생물ㆍ화학ㆍ환경>생명과학
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강의설명
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A new paradigm is emerging in which plants utilize proteins and RNA as non-cell-autonomously acting signaling macromolecules to mediate local and long-distance regulation over physiological and developmental processes. The cell-to-cell pathway for the trafficking of these non-cell-autonomous proteins (NCAPs) and RNA, in the form of ribonucleoprotein (RNP) complexes, is established by plasmodesmata (PD), the intercellular organelles unique to plants. The interconnection of local tissues to the phloem sieve tube system, through PD, establishes an integrated supracellular organism. Regulation of these local and long-distance macromolecular trafficking networks is essential for the coordinated exchange of information between distantly located plant organs to orchestrate events at the whole plant level. In angiosperms, the sieve tube system is comprised of two main cell types, the sieve elements (SEs) and their associated companion cells (CCs). At maturity, the enucleate SEs are highly modified to a low-resistance pathway, the sieve tube, for the translocation of photoassimilates; CCs function in the maintenance of the associated SEs. Mass spectrometry-based analysis of the phloem sap has established that the translocation stream contains a complex set of proteins (~ 2000 in number). Detailed analyses of many of these phloem proteins have demonstrated their capacity for cell-to-cell movement through PD: thus, the entry and exit of these phloem proteins appears to be regulated by the CC-SE PD. A number of these phloem proteins can bind to RNA and these RBPs mediate the cell-to-cell and long-distance translocation of RNA.
These studies provide support for the concept that the CC-SE complex has the machinery necessary to mediate long-distance delivery of NCAPs and RNPs. This notion is consistent with the discovery that the phloem translocation stream contains a specific population of RNA molecules (>1,500 mRNA and many 1000s of si/miRNA species). Grafting experiments sho
