Thermospermine is required for stem elongation in Arabidopsis thaliana
Thermospermine is required for stem elongation in Arabidopsis thaliana
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DOI：
10.1093/pcp/pcn109
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发表时间：
2008-09-01
影响因子：
4.9
通讯作者：
Takahashi, Taku
中科院分区：
文献类型：
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作者：
Kakehi, Jun-ichi;Kuwashiro, Yoshitaka;Takahashi, Taku
拟南芥ACAULIS5 （ACL5）基因的功能缺失突变体在茎伸长方面存在严重缺陷。ACL5先前被报道编码精胺合成酶。然而，最近的一项研究表明，细菌表达的重组ACL5蛋白催化亚精胺转化为热精胺（精胺的一种结构异构体），而不是转化为精胺。在本研究中，我们发现在野生型幼苗中检测到热精胺，而在acl5-1突变体中未检测到。我们进一步研究了外源施用这些异构体对acl5-1生长的影响。每天在茎尖处施用0.1 mM的热精胺可以部分恢复acl5-1的矮化表型，而精胺对突变体的形态没有影响。外源热精胺降低了ACL5 -1幼苗中远高于野生型幼苗的ACL5 -1转录水平。因此，我们得出结论，热精胺确实是通过ACL5的作用产生的，并且是拟南芥茎伸长所必需的。
Loss-of-function mutants of the ACAULIS5 (ACL5) gene in Arabidopsis thaliana have severe defects in stem elongation. ACL5 was previously reported as encoding a spermine synthase. A more recent study, however, showed that the bacterial expressed recombinant ACL5 protein catalyzes the conversion of spermidine to thermospermine, a structural isomer of spermine, rather than to spermine. In the present study, we found that thermospermine was detected in wild-type seedlings but was not detectable in the acl5-1 mutant. We further examined the effect of exogenous application of these isomers on the growth of acl5-1. Daily application of 0.1 mM thermospermine onto the shoot apex partially rescued the dwarf phenotype of acl5-1, while that of spermine had no effects on the morphology of the mutant. The acl5-1 transcript level in acl5-1 seedlings, which is much higher than the ACL5 transcript level in wild-type seedlings, was reduced by exogenous thermospermine. Thus we conclude that thermospermine is indeed produced through the action of ACL5 and required for stem elongation in Arabidopsis.