Cloning, characterization and functional analysis of novel 6-kestose exohydrolases (6-KEHs) from wheat (Triticum aestivum)
Cloning, characterization and functional analysis of novel 6-kestose exohydrolases (6-KEHs) from wheat (Triticum aestivum)
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DOI：
10.1111/j.1469-8137.2005.01394.x
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发表时间：
2005-06-01
期刊：
影响因子：
9.4
通讯作者：
Kawakami, A
中科院分区：
文献类型：
--
作者：
Van den Ende, W;Yoshida, M;Kawakami, A
谷物积累禾本科型果聚糖，其通过果聚糖1-外切水解酶（1-FEH）和果聚糖6-外切水解酶（6-FEH）进行胁迫相关降解。为了寻找与抗冻性相关的FEH基因，从抗寒小麦冠层cDNA文库中筛选出两个新的6-酮糖苷酶（6-KEH）同工酶，并对其进行了分离纯化和鉴定。北方杂交结果表明，6-KEH转录本从秋季到冬季在冠层组织中表达水平基本一致，但在叶组织中表达水平不一致。质外体液体分离和活性测量强烈表明6-KEH位于质外体中。有人认为6-KEH与其他FEH一起可能参与质外体果聚糖的分解，这可能在应激下发挥膜保护剂的作用。或者，不能排除在信号传导过程中或在细菌来源的外源性6-蔗果三糖降解中的作用。
Cereals accumulate graminan-type fructans which are subject to stress-related degradation by fructan 1-exohydrolases (1-FEHs) and fructan 6-exohydrolases (6-FEHs). To find new FEH genes related to freezing tolerance, a cold-hardened wheat crown cDNA library was screened.Here we report the cloning, purification and characterization of two novel 6-kestosidase (6-KEH) isoenzymes from wheat crowns (Triticum aestivum). Functional characterization in Pichia pastoris confirmed the extreme substrate selectivity for the fructan trisaccharide 6-kestose.Northern blotting showed that 6-KEH transcripts were constantly detected at the same level from autumn to winter in crown but not in leaf tissues. Apoplastic fluid isolations and activity measurements strongly suggest that 6-KEH is localized in the apoplast.It is proposed that 6-KEHs, together with other FEHs, might be involved in the breakdown of apoplastic fructans which may fulfil a role as membrane protectors under stress. Alternatively, a role in signalling processes, or in the degradation of exogenous 6-kestose from bacterial origin, cannot be excluded.