PLANT PHYSIOLOGY , Vol 101, Issue 3 809-817, Copyright © 1993 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
Isolation and Characterization of a cDNA Clone for Plant Nuclear Antigen 21D7 Associated with Cell Division
M. W. Smith, M. Ito, T. Yamada, T. Suzuki and A. Komamine
Biological Institute, Faculty of Science, Tohoku University, Aoba-yama, Sendai 980 (M.W.S., M.I., A.K.)
A cDNA clone was isolated from a carrot (Daucus carota L.) cDNA expression
library using monoclonal antibody 21D7, which recognizes a nuclear antigen
associated with cell division in plant cells. To show that the isolated
cDNA encodes the 21D7 antigen, a polyclonal antiserum was raised against a
recombinant fusion protein specified by the cDNA. Both the polyclonal
antiserum and the monoclonal antibody 21D7 recognized the same plant
protein on immunoblots, in immunoprecipitation experiments, and in peptide
mapping. Analysis of the cDNA revealed that the deduced amino acid sequence
has 45% identity to the predicted sequence of the mouse transplantation
antigen P91A from mutant tumor cells that is responsible for the immune
rejection of the corresponding cell clone in syngeneic mouse. The
expression of the plant cDNA at the mRNA level was highly correlated with
cell proliferation. In suspension cultures of Catharanthus roseus (L.) G
Don. cells, the highest level of expression was observed during the
midlogarithmic phase of growth. When auxin was added to stimulate cell
division of auxin-starved cells arrested in the G1 phase, transcription was
immediately enhanced, and the level of expression remained high throughout
the G1 and S phases and dropped dramatically at the end of DNA replication.