The OPT family functions in long-distance peptide and metal transport in plants.
The OPT family functions in long-distance peptide and metal transport in plants.
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DOI：
10.1007/0-387-25856-6_3
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发表时间：
2006-01-01
期刊：
影响因子：
--
通讯作者：
Lubkowitz, Mark
中科院分区：
文献类型：
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作者：
Lubkowitz, Mark
OPT家族在六年前首次被描述，在理解这些转运蛋白在各自生物体中的作用方面取得了很大进展。植物是唯一的生物体，其中YS-和PT-型转运蛋白已被表征，所有这些OPTs似乎是质膜结合蛋白，这表明它们从质外质或环境中输入底物。YS 1是唯一已知的从根际转运底物的OPT，而所有其他的OPT似乎在肽或金属的长距离运输中起作用。本综述中涵盖的所有研究的总和表明，图4中所示的植物中OPT功能的模型。肽、金属-NA和金属-MAs络合物（仅策略II植物）被装载到根中的木质部流中用于长距离运输。OPTs通过将底物输入到库组织（如叶片）和通过转运韧皮部来卸载木质部。肽和金属-NA络合物共质体地离开叶或通过OPTs从质外质输入到韧皮部。子代组织（胚乳和胚）与母体组织是质外体分离的，OPTs也可以在装载发育中的种子中起作用。同样，幼苗与胚乳共质体分离，OPTs可以帮助将营养物质转移到生长的植物中。在过去的两年里，在理解植物中的OPTs方面取得了很大进展，尽管有几个基本问题仍然没有答案。也就是说，冗余程度如何？YS和PT OPTs之间是否有任何底物重叠？他们各自的角色有多重要？除了肽和金属转运外，还有其他功能吗？考虑到最近的发现速度，我们可能不必等待很长时间就能找到答案。
The OPT family was first described six years ago, and much progress has been made in understanding the role these transporters play in their respective organisms. Plants are the only organisms in which both YS- and PT-type transporters have been characterized, and all of these OPTs appear to be plasma membrane-bound proteins, suggesting that they import substrates from the apoplasm or the environment. YS1 is the only OPT known to translocate substrates from the rhizosphere, whereas all the other OPTs seem to function in long-distance transport of peptides or metals. The sum of all the studies covered in this review suggest the model for OPT function in plants depicted in Figure 4. Peptides, metal-NA, and metal-MAs complexes (Strategy II plants only) are loaded into the xylem stream in the root for long-distance transport. OPTs unload the xylem by importing substrates into sink tissues such as leaves and by transloading the phloem. Peptides and metal-NA complexes exit the leaf symplasmically or by importation into the phloem from the apoplasm by OPTs. The filial tissues (endosperm and embryo) are apoplasmically separated from the maternal tissues, and OPTs may also function in loading the developing seed. Similarly, seedlings are symplasmically disconnected from the endosperm and OPTs may help move nutrients to the growing plant. Much progress has been made in the last two years toward understanding OPTs in plants, although several fundamental questions remain unanswered. Namely, what is the level of redundancy? Is there any substrate overlap between YS and PT OPTs? How crucial are their respective roles? Are there additional functions beyond peptide and metal transport? Given the recent pace of discovery, we may not have to wait long to find out the answers.