Poster: Vegetative Development

Abs # 419: Analysis of the vascular-network defective mutant, van4, of　Arabidopsis　thaliana

Presenter:	Naramoto, Satoshi , ss16379@mail.ecc.u-tokyo.ac.jp
Authors	Naramoto, Satoshi  (A)   Koizumi, Koji  (B)   Shinichiro, Sawa  (A)   Iwamoto, kuninori  (A)   Sugiyama, Munetaka  (C)   Fukuda, Hiroo  (A) (D)
Affiliations:	(A): Department of Biological Sciences, Graduate School of Science, The University of Tokyo (B): Department of Bioscience, Faculty of Applied Bioscience, Tokyo University of Agriculture (C): Botanical Gardens, Graduate School of Science, The University of Tokyo (D): Plant Science Center, RIKEN

To elucidate molecular mechanisms of spatial regulation of vascular development, we have isolated and analyzed van mutants of Arabidopsis that are characterized by aberrant vascular patterns. Here we report the isolation of the VAN4 gene and its expression patterns. Fine chromosome mapping of the van4 mutation localized it at the position of 9.2 cM of chromosome V. Sequencing of this region revealed that a single base substitution, C to T, exists in one of the predicted CDS of the van4 genome. Introduction of the corresponding wild-type genome fragment into the van4 explants rescued their defect. This result led to the conclusion that the above-mentioned CDS corresponds to the VAN4 gene. The predicted product of the VAN4 gene shares sequence similarity with gene products of various organisms including rice, human, and Drosophila, for any of which information about functions is not available. RNA gel blot analysis showed that the VAN4 mRNA was present in all organs surveyed, and detected low level expression in mature leaves and stems and high levels in roots and floral organs. Furthermore, we tested the temporal and spatial pattern of VAN4 expression by b – glucuronidase (GUS) reporter analysis. The expression pattern was changed drastically according to the stage of organs. In the shoot apical meristem and a leaf primodium, the expression of VAN4 was observed uniformly. As the primodium developed, the expression became restricted to the provascular tissues, and finally to the vascular bundles. The same expression patterns were observed in roots and floral organs. In summary, VAN4 appeared to be expressed predominantly in cells that are uncommitted to differentiation.