Journal Article

Transgenic Tobacco Over-Expressing a Homeobox Gene Shows a Developmental Interaction between Leaf Morphogenesis and Phyllotaxy

Masanori Tamaoki, Asuka Nishimura, Mitsuhiro Aida, Masao Tasaka and Makoto Matsuoka

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 7, pages 657-667
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029590
Transgenic Tobacco Over-Expressing a Homeobox Gene Shows a Developmental Interaction between Leaf Morphogenesis and Phyllotaxy

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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.

Keywords: Homeobox gene; Micro-surgical experiment; Nicotiana tabacum; Phyllotaxy; Plastochron ratio; Transgenic plant

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry ; Biochemistry ; Molecular and Cell Biology

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