Tamaoki M, Nishimura A, Aida M, Tasaka M, Matsuoka M
Nagoya University, BioScience Center, Aichi, Japan.
Plant Cell Physiol. 1999 Jul;40(7):657-67. doi: 10.1093/oxfordjournals.pcp.a029590.
The tobacco gene, NTH1, encodes a polypeptide of 326 amino acids and is a member of the class1 KN1-type family of homeobox genes. Expression of NTH1 has mainly been observed in vegetative and reproductive shoot apices, not observed in roots or expanded leaves. Over-expression of NTH1 in transgenic plants caused abnormal leaf morphology, consisting of wrinkling and curvature. Interestingly, the direction of leaf curvature tended to be conserved among almost all of the leaves in any given transformant. In transgenic plants exhibiting clockwise or anticlockwise phyllotaxy, leaves curved to the right or left, respectively, when looking from the shoot apex toward the base. Micro-surgical experiments demonstrated that the presence of the shoot apex is necessary for the development of leaf curvature, indicating that the order of formation of leaves on the stem (the generative spiral) affects leaf development. We found a correlation between the severity of leaf curvature and the value of the plastochron ratio, a parameter of phyllotaxy. Transformants with more severe phenotypes had larger plastochron ratios. From these findings, we discuss the possibility that an increase in the plastochron ratio, caused by over-expression of NTH1 in the shoot apex, may be involved in leaf curvature.
烟草基因NTH1编码一个由326个氨基酸组成的多肽，是同源异型盒基因中第1类KN1型家族的成员。NTH1的表达主要在营养和生殖茎尖中观察到，在根或展开的叶片中未观察到。在转基因植物中过表达NTH1会导致叶片形态异常，包括起皱和弯曲。有趣的是，在任何给定的转化体中，几乎所有叶片的弯曲方向往往是一致的。在表现出顺时针或逆时针叶序的转基因植物中，从茎尖向基部看时，叶片分别向右或向左弯曲。显微手术实验表明，茎尖的存在对于叶片弯曲的发育是必需的，这表明茎上叶片形成的顺序（发生螺旋）会影响叶片发育。我们发现叶片弯曲的严重程度与叶序参数叶龄比的值之间存在相关性。具有更严重表型的转化体具有更大的叶龄比。基于这些发现，我们讨论了由于茎尖中NTH1过表达导致叶龄比增加可能与叶片弯曲有关的可能性。
