鋸歯とはなにか？：葉っぱの形態形成とのホモロジー

鋸歯とはなにか？　　　はいそこの病理の先生、お答えください。といって正確にお答えを返される先生は何人いることだろう？ まずこれはなんと読むか？ 「のこぎりば」である。というのは嘘ではないが、医学生物学の分野では一般的ではない。「きょし」と呼びます。「きょしじょうびょうへん」 先ほどの「のこぎりば」ということから、これはノコギリ（鋸）の歯の並びを表す言葉である。と同時に植物の葉っぱの辺縁のぎざぎざを表す言葉である。　google imageによると・・・・・・・


葉っぱの形を記述する用語なんだね。

















低鋸歯、整生鋸歯、重鋸歯なんていう言葉もある。イメージが膨らんだでしょうか？

大腸ポリープの形態形成と葉っぱの辺縁の形態形成に類似点を求めて研究している人はいないのだろうか？今後の病理学に面白さを求めるとすればこのあたりに突破口はあるのではないだろうか？形態形成に興味が持てない病理研究者は廃業したほうがいい。


葉の縁のギザギザ「鋸歯」ができる仕組みを解明


河村　英子（東京大学大学院理学系研究科生物科学専攻　元特任研究員）
堀口　吾朗（立教大学理学部生命理学科　准教授）
塚谷　裕一（東京大学大学院理学系研究科生物科学専攻　教授）



Plant J. 2010 May;62(3):429-41. Epub 2010 Feb 1.
Mechanisms of leaf tooth formation in Arabidopsis.

Kawamura E, Horiguchi G, Tsukaya H.

Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract

Serration found along leaf margins shows species-specific characters. Whereas compound leaf development is well studied, the process of serration formation is largely unknown. To understand mechanisms of serration development, we investigated distinctive features of cells that could give rise to tooth protrusion in the simple-leaf plant Arabidopsis. After the emergence of a tooth, marginal cells, except for cells at the sinuses and tips, started to elongate rapidly. Localized cell division seemed to keep cells at the sinus smaller, rather than halt cell elongation. As leaves matured, the marginal cell number between teeth became similar in any given tooth. These results suggest that teeth are formed by repetition of an unknown mechanism that spatially monitors cell number and regulates cell division. We then examined the role of CUP-SHAPED COTYLEDON 2 (CUC2) in serration development. cuc2-3 forms fewer hydathodes and auxin maxima, visualized by DR5rev::GFP, at the leaf margin, suggesting that CUC2 patterns serration through the regulation of auxin. In contrast to a previous interpretation, comparison of leaf outlines revealed that CUC2 promotes outgrowth of teeth rather than suppression of growth at the sinuses. We found that mutants with increased CUC2 expression form ectopic tissues and mis-express SHOOT MERISTEMLESS (STM) at the sinus between the enhanced teeth. Similar but infrequent STM expression was found in the wild type, indicating STM involvement in the serration of simple leaves. Our study provides insights into the morphological and molecular mechanisms for leaf development and tooth formation, and highlights similarities between serration and compound leaf development.