PLANT PHYSIOLOGY , Vol 104, Issue 4 1151-1157, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
Analysis of the rolC Promoter Region Involved in Somatic Embryogenesis-Related Activation in Carrot Cell Cultures
N. Fujii, R. Yokoyama and H. Uchimiya
Institute of Molecular and Cellular BioSciences, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan (N.F., H.U.)
In cell cultures of carrot (Daucus carota L.), somatic embryogenesis can be
induced by transferring cells from a medium containing
2,4-dichlorophenoxyacetic acid (2,4-D) to one devoid of 2,4-D. Previous
analysis of transgenic carrot cells containing the 5[prime] noncoding
sequence of the Ri plasmid rolC and a structural gene for bacterial
[beta]-glucuronidase (uidA) has shown that the chimeric gene is actively
expressed after induction of somatic embryogenesis. In this study, we
demonstrate that activation of the rolC promoter is dependent on the
process of embryo development but not on the duration of the cell culture
in 2,4-D-free medium. We also analyzed the cis region of the rolC promoter
that is responsible for somatic embryogenesis-related activation (SERA),
namely relatively low [beta]-glucuronidase (GUS) activity in calli and
proembryogenic masses (PEM) and high GUS activity in heart- and
torpedo-stage embryos. When the -255-bp region of the rolC gene was used,
SERA was retained. Internal deletions within this -255-bp region did not
alter SERA by the rolC promoter. Furthermore, when a rolC promoter fragment
(-848 to -94 bp) was fused to the cauliflower mosaic virus (CaMV) 35S core
region (-90 to +6 bp), it conferred relatively low GUS activity in calli
and PEM but high GUS activity in heart and torpedo embryos. When -848- to
-255-bp or -255- to -94-bp fragments of the rolC promoter were fused to the
same CaMV 35S core region, GUS activity patterns were not related to
somatic embryogenesis. These results suggest that the combination of
several regulatory regions in the rolC promoter may be required for SERA in
carrot cell cultures.