Pp6-FEH1 encodes an enzyme for degradation of highly polymerized levan and is transcriptionally induced by defoliation in timothy (Phleum pratense L.).
Pp6-FEH1 encodes an enzyme for degradation of highly polymerized levan and is transcriptionally induced by defoliation in timothy (Phleum pratense L.).
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DOI：
10.1093/jxb/err018
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发表时间：
2011-06
影响因子：
6.9
通讯作者：
Yoshida M
中科院分区：
文献类型：
--
作者：
Tamura KI;Sanada Y;Tase K;Komatsu T;Yoshida M
草在被砍伐或放牧落叶后的再生能力是它们生存的重要因素，也是它们用作饲料作物时的一个重要性状。在积累果聚糖的温带草物种中，落叶诱导果聚糖外切水解酶（FEH）的活性，所述果聚糖外切水解酶降解果聚糖以作为再生的碳源。在这里，从梯牧草中克隆了一个cDNA，命名为Pp 6-FEH 1，它显示出与小麦果聚糖6-外切水解酶（6-FEH）的相似性。该重组酶能完全降解梯牧草冠部组织中的果聚糖，其中主要是高聚合度的β（2，6）-连接和线性果聚糖（莱万）。Pp 6-FEH 1的底物特异性不同于先前在果聚糖积累植物中表征的具有6-FEH活性的酶：（i）Pp 6-FEH 1对莱万显示6-FEH活性（平均DP 20）比对6-酮三糖（DP 3）高4倍，表明Pp 6-FEH 1对具有高DP的β（2，6）-连接的果聚糖具有偏好;（ii）Pp 6-FEH 1对β（2，1）-连接的果聚糖具有显著的活性，但显著低于对β（2，6）-连接的果聚糖的活性;（iii）Pp 6-FEH 1具有弱的转化酶活性，其6-FEH活性被蔗糖轻微抑制。在残茬的幼苗和年轻的单倍体从成年梯牧草植物，转录Pp 6-FEH 1显着增加3小时内落叶，其次是6-FEH活性的增加和果聚糖的降解。这些结果表明，Pp 6-FEH 1发挥作用，在果聚糖的降解和动员的碳源，在梯牧草落叶后再生长。
The ability of grasses to regrow after defoliation by cutting or grazing is a vital factor in their survival and an important trait when they are used as forage crops. In temperate grass species accumulating fructans, defoliation induces the activity of a fructan exohydrolase (FEH) that degrades fructans to serve as a carbon source for regrowth. Here, a cDNA from timothy was cloned, named Pp6-FEH1, that showed similarity to wheat fructan 6-exohydrolase (6-FEH). The recombinant enzyme expressed in Pichia pastoris completely degraded fructans that were composed mainly of β(2,6)-linked and linear fructans (levan) with a high degree of polymerization (DP) in the crown tissues of timothy. The substrate specificity of Pp6-FEH1 differed from previously characterized enzymes with 6-FEH activity in fructan-accumulating plants: (i) Pp6-FEH1 showed 6-FEH activity against levan (mean DP 20) that was 4-fold higher than against 6-kestotriose (DP 3), indicating that Pp6-FEH1 has a preference for β(2,6)-linked fructans with high DP; (ii) Pp6-FEH1 had significant activity against β(2,1)-linked fructans, but considerably less than against β(2,6)-linked fructans; (iii) Pp6-FEH1 had weak invertase activity, and its 6-FEH activity was inhibited slightly by sucrose. In the stubble of seedlings and in young haplocorms from adult timothy plants, transcripts of Pp6-FEH1 were significantly increased within 3 h of defoliation, followed by an increase in 6-FEH activity and in the degradation of fructans. These results suggest that Pp6-FEH1 plays a role in the degradation of fructans and the mobilization of carbon sources for regrowth after defoliation in timothy.
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影响因子：
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