Olszewski Neil E, West Christopher M, Sassi Slim O, Hartweck Lynn M
Department of Plant Biology, Microbial and Plant Genomics Institute, 250 Biological Sciences Center, 1445 Gortner Ave., St. Paul, MN 55108, USA.
Biochim Biophys Acta. 2010 Feb;1800(2):49-56. doi: 10.1016/j.bbagen.2009.11.016. Epub 2009 Dec 2.
The role in plants of posttranslational modification of proteins with O-linked N-acetylglucosamine and the evolution and function of O-GlcNAc transferases responsible for this modification are reviewed. Phylogenetic analysis of eukaryotic O-GlcNAc transferases (OGTs) leads us to propose that plants have two distinct OGTs, SEC- and SPY-like, that originated in prokaryotes. Animals and some fungi have a SEC-like enzyme while plants have both. Green algae and some members of the Apicomplexa and amoebozoa have the SPY-like enzyme. Interestingly the progenitor of the Apicomplexa lineage likely had a photosynthetic plastid that persists in a degenerated form in some species, raising the possibility that plant SPY-like OGTs are derived from a photosynthetic endosymbiont. OGTs have multiple tetratricopeptide repeats (TPRs) that within the SEC- and SPY-like classes exhibit evidence of strong selective pressure on specific repeats, suggesting that the function of these repeats is conserved. SPY-like and SEC-like OGTs have both unique and overlapping roles in the plant. The phenotypes of sec and spy single and double mutants indicate that O-GlcNAc modification is essential and that it affects diverse plant processes including response to hormones and environmental signals, circadian rhythms, development, intercellular transport and virus infection. The mechanistic details of how O-GlcNAc modification affects these processes are largely unknown. A major impediment to understanding this is the lack of knowledge of the identities of the modified proteins.
本文综述了蛋白质O-连接的N-乙酰葡糖胺糖基化修饰在植物中的作用，以及负责这种修饰的O-连接N-乙酰葡糖胺转移酶（OGT）的进化和功能。对真核生物OGT的系统发育分析使我们提出，植物有两种不同的OGT，即SEC样和SPY样，它们起源于原核生物。动物和一些真菌有一种SEC样酶，而植物同时拥有这两种酶。绿藻以及顶复门和变形虫门的一些成员拥有SPY样酶。有趣的是，顶复门谱系的祖先可能有一个光合质体，在某些物种中以退化形式存在，这增加了植物SPY样OGT来源于光合内共生体的可能性。OGT有多个四肽重复序列（TPR），在SEC样和SPY样类别中，特定重复序列显示出强烈的选择压力迹象，表明这些重复序列的功能是保守的。SPY样和SEC样OGT在植物中既有独特作用，也有重叠作用。sec和spy单突变体及双突变体的表型表明，O-连接N-乙酰葡糖胺修饰至关重要，且它影响多种植物过程，包括对激素和环境信号的响应、昼夜节律、发育、细胞间运输和病毒感染。O-连接N-乙酰葡糖胺修饰如何影响这些过程的机制细节在很大程度上尚不清楚。理解这一点的一个主要障碍是缺乏对被修饰蛋白质身份的了解。
