Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Yin, Xiaofeng [1], Tsukaya, Hirokazu [2].

Development and Morphogenesis of Flattened Unifacial leaves in Juncus prismatocarpus (Juncaceae).

Unifacial leaves are leaves that partially lack the adaxial surface. Despite being extensively studied from the comparative morphology perspective some forty years ago, knowledge about development and morphogenesis of unifacial leaves is still lacking. Using molecular and genetics approaches, we showed that the leaf sheath of Juncus prismatocarpus was bifacial while its leaf blade was unifacial (abaxialized) at the molecular level and the flattening of the leaf blade was controlled by DROOPING LEAF (DL), a YABBY class transcriptional factor. Next, in order to analyze how cell proliferation shapes the morphogenesis of the leaf blade of J. prismatocarpus, which is cylindrical (terete) early in development but later becomes flattened (ensiform), we invented a pulse-chase EdU method. This rapid and efficient method can be applied to model and non-model plant species. Using this method, we quantified and mapped cell division direction on the leaf blade of J. prismatocarpus. We found that cell divisions in the thickening direction were the most abundant (> 45%) among all directions from the early plastochron 2 (P2) stage through the P3 stage. Mapping of cell divisions indicated that cell divisions in a particular direction were not restricted to a particular domain but were distributed diffusely throughout the entire cross-sectional area of the leaf blade. Further gradient analysis revealed that the distribution of cell divisions in the thickening direction was denser in the adaxial domain than that in the abaxial domain. In addition, contrary to the prolonged and diffuse distribution of cell divisions in the thickening direction, the expression of DL was transient and only in a narrow band of ca. 2-3 cells, indicating DL may work non-cell-autonomously in terms of promoting cell divisions in the thickening direction. Our results suggest that a diffuse “thickening meristem”, instead of a restricted “adaxial meristem” as suggested by classic comparative morphology studies, plays the key role in the development and morphogenesis of unifacial leaves.

1 - The University Of Tokyo, Biology, Department Of Biological Sciences, Graduate School Of Science, Hongo 7-3-1, Science Building 2, Bunkyo-ku, Tokyo, 113-0033, Japan
2 - The University Of Tokyo, GRADUATE SCHOOL OF SCIENCE, Science Building #2, Univ. Tokyo, HONGO, BUNKYO-KU, Tokyo, 113-0033, Japan

cell division direction
Juncus prismatocarpus
thickening meristem
unifacial leaf.

Presentation Type: Oral Paper
Number: 0004
Abstract ID:475
Candidate for Awards:None

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