Analysis of xyloglucan endotransglucosylase/hydrolase (XTH) gene families in kiwifruit and apple
Analysis of xyloglucan endotransglucosylase/hydrolase (XTH) gene families in kiwifruit and apple
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DOI：
10.1016/j.postharvbio.2008.06.014
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发表时间：
2009-02-01
影响因子：
7
通讯作者：
Schroder, Roswitha
中科院分区：
文献类型：
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作者：
Atkinson, Ross G.;Johnston, Sarah L.;Schroder, Roswitha
木葡聚糖内转葡糖基酶/水解酶 (XTH) 酶被认为在果实成熟中发挥关键作用，其作用是通过松开细胞壁，为其他细胞壁相关酶的进一步修饰做好准备，并通过分解木葡聚糖。从包含超过 270,000 个表达序列标签 (EST) 的猕猴桃和苹果数据库中分离和表征了 25 个 XTH 基因。 XTH 基因（14 个来自猕猴桃，11 个来自苹果）编码具有相似分子量的推定蛋白质，但等电点范围从酸性到碱性。所有 25 个 XTH 氨基酸序列均含有 XTH 酶活性位点的两个保守谷氨酸残基。系统发育分析产生了具有分支的树，每个分支都包含猕猴桃、苹果、番茄和拟南芥 XTH 序列，这表明功能直系同源的潜力。使用EST表达谱和定量PCR分析来鉴定在根尖、花、幼叶和成熟果实中表达的猕猴桃和苹果XTH转录本。在成熟的苹果果实中，两个 XTH 基因（Md-XTH2 和 Md-XTH10）的转录本最丰富，而在成熟的猕猴桃中，三个转录本占主导地位（Ad-XTH4、5 和 7）。 Ad-XTH7 在商业收获时坚硬的猕猴桃的外果皮中高度表达，并且该 mRNA 的表达在快速软化阶段下降。三个猕猴桃XTH基因（Ad-XTH5、Ad-XTH7和Ac-XTH14）在大肠杆菌中表达，重组蛋白显示出具有木葡聚糖内转葡糖基酶活性。这项研究为了解 XTH 在猕猴桃和苹果果实成熟和储存过程中的作用奠定了基础。 (C) 2008 Elsevier B.V. 保留所有权利。
Xyloglucan endotransglucosylase/hydrolase (XTH) enzymes are thought to play a key role in fruit ripening by loosening the cell wall in preparation for further modification by other cell wall-associated enzymes and through disassembly of xyloglucan. Twenty-five XTH genes were isolated and characterised from kiwifruit and apple databases containing >270,000 expressed sequence tags (ESTs). The XTH genes (14 from kiwifruit, 11 from apple) encoded Putative proteins with similar molecular weights, but with isoelectric points ranging from acidic to basic. All 25 XTH amino acid sequences contained the two conserved glutamic acid residues at the active site of the XTH enzyme. Phylogenetic analysis produced trees with branches each containing kiwifruit, apple, tomato and Arabidopsis XTH sequences, suggesting the potential for functional orthology. EST expression profiling and quantitative PCR analysis were used to identify kiwifruit and apple XTH transcripts expressed in root tip, flower, Young leaf and ripe fruit. In ripe apple fruit, the transcripts for two XTH genes (Md-XTH2 and Md-XTH10) were the most abundant, whilst in ripe kiwifruit three transcripts predominated (Ad-XTH4, 5 and 7). Ad-XTH7 was highly expressed in the outer pericarp of firm kiwifruit at commercial harvest and expression of this mRNA decreased during the rapid softening phase. Three kiwifruit XTH genes (Ad-XTH5, Ad-XTH7 and Ac-XTH14) were expressed in Escherichia coli and the recombinant proteins were shown to have xyloglucan endotransglucosylase activity. This research lays the groundwork for understanding the role of XTHs during fruit ripening and storage in kiwifruit and apple. (C) 2008 Elsevier B.V. All rights reserved.