Molecular mechanism of vascular system formation

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1. Analysis with Arabidopsis vascular mutants, van1-van7 : Molecular analysis of Arabidopsis vascular mutants, van1-van7 with a pAthb8-GUS or pTED3-GUS fusion gene revealed that defects of these mutants were caused by abnormal pattern formation of procambial cells. In addition, we displayed that the continuity of the vascular network is more sensitive to genetic lesions than their overall architecture is, supporting the diffusion-reaction prepattern model.2. Analysis of the HD-Zip homeobox genes during carrot somatic embryogenesis. We analyzed expression pattern of 6 HD-Zip homeobox genes, CHB1-CHB6, with in situ hybridization during carrot somatic embryogenesis, and revealed that all the genes were expressed in association with vascular cells in the late stage of embryogesesis, that is, CHB6 was expressed specifically in procambium and others were in different vascular cells. These results suggest that the HD-Zip homeobox genes are involved in vascular formation.3. Analysis of vascula … More r cell differentiation with an in vitro Zinnia system in which mesophyll cells differentiate into vascular cells.(1) We revealed the presence of different kind of vascular cells in the in vitro Zinnia culture system.(2) We established new culture methods, with which a tracheary element-inducing factor was partially purified. The partially purified substance was a high molecular weight-arabinogalactan protein and designated "xylogen".(3) We found that brassinosteroids were synthesized prior to Stage 3 of differentiation and their biosynthesis was regulated by a coordinated increase in transcription of genes encoding brassinosteroid biosynthesis. In addition, our finding that castasterone, an active brassinosteroid, is secreted preferentially out of the cell and accumulates in medium, suggests that brassinosteroids function at extracellular surface of the cell.(4) Using a phage display subtraction method, we succeeded in isolating of three novel antibodies recognizing cell walls of specific vascular cells. Less