A dual role of tobacco hexokinase 1 in primary metabolism and sugar sensing
A dual role of tobacco hexokinase 1 in primary metabolism and sugar sensing
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DOI：
10.1111/pce.12060
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发表时间：
2013-07-01
影响因子：
7.3
通讯作者：
Hajirezaei, Mohammad-Reza
中科院分区：
文献类型：
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作者：
Kim, Young-Min;Heinzel, Nicolas;Hajirezaei, Mohammad-Reza
己糖激酶（HXK）存在于几乎所有活的生物体中，并且是催化己糖的ATP依赖性磷酸化的碳水化合物代谢的中心。在植物中，HXKs被认为是糖传感器和/或与直接提供代谢途径的其他酶相互作用，如糖酵解、核苷酸磷酸单糖（NDP-葡萄糖）途径和戊糖磷酸途径。我们鉴定了烟草HXK基因家族的9个成员，并观察到在这9个NtHXKs的RNAi株系中，只有NtHXK 1的RNAi株系表现出改变的表型，即生长受阻和叶片失绿。NtHXK 1也是所有NtHXKs中相对表达水平最高的同种型。GFP标记和免疫定位表明NtHXK 1与线粒体膜相关。NtHXK 1的过表达导致叶提取物或叶绿体中葡萄糖磷酸化活性升高。此外，NtHXK 1能够补充葡萄糖不敏感的拟南芥突变体gin 2 -1，表明NtHXK 1可以接管葡萄糖传感功能。NtHXK 1的RNAi株系表现出叶片和叶绿体结构严重受损，同时淀粉过量积累。我们的结论是，NtHXK 1不仅是必不可少的维持糖酵解活性在呼吸过程中，但也调节淀粉周转，特别是在夜间。
Hexokinase (HXK) is present in all virtually living organisms and is central to carbohydrate metabolism catalysing the ATP-dependent phosphorylation of hexoses. In plants, HXKs are supposed to act as sugar sensors and/or to interact with other enzymes directly supplying metabolic pathways such as glycolysis, the nucleotide phosphate monosaccharide (NDP-glucose) pathway and the pentose phosphate pathway. We identified nine members of the tobacco HXK gene family and observed that among RNAi lines of these nine NtHXKs, only RNAi lines of NtHXK1 showed an altered phenotype, namely stunted growth and leaf chlorosis. NtHXK1 was also the isoform with highest relative expression levels among all NtHXKs. GFP-tagging and immunolocalization indicated that NtHXK1 is associated with mitochondrial membranes. Overexpression of NtHXK1 resulted in elevated glucose phosphorylation activity in leaf extracts or chloroplasts. Moreover, NtHXK1 was able to complement the glucose-insensitive Arabidopsis mutant gin2-1 suggesting that NtHXK1 can take over glucose sensing functions. RNAi lines of NtHXK1 showed severely damaged leaf and chloroplast structure, coinciding with an excess accumulation of starch. We conclude that NtHXK1 is not only essential for maintaining glycolytic activity during respiration but also for regulating starch turnover, especially during the night.