Download Identification of a Cell Cycle-Related Cene, Cyclin, in Nicotiana

Plant Physiol. (1995) 108: 425-426
Plant Gene Register
Identification of a Cell Cycle-Related Cene, Cyclin, in
Nicotiana tabacum (1.)
Li-Xian Qin*, Luc Richard, Claudette Perennes, Pierre Gadal, and Catherine Bergounioux
lnstitut de Biotechnologie des Plantes, Université Paris-Sud, Bât. 630, Plateau du Moulon, F-91400 Orsay,
France (L.-X.Q., C.P., P.G., C.B.); and Département de Biologie Supramoléculaire et Cellulaire,
lnstitut Jacques Monod, 2 place jussieu, F-75251 Paris cedex 05, France (L.R.)
Among a11 of the proteins known to be involved in the
cell cycle, the CDKs are key components in the control of
both the G, to S phase and the G, to M phase transitions in
a11 eukaryotes (Jacobs, 1992; Nigg, 1993). The kinase activity of CDKs is regulated by subunits called cyclins, which
are involved in the modification of the phosphorylation
state, the specificity, and the subcellular location of the
enzymes. Although these mechanisms are supposed to occur in a11 eukaryotes, the multiplicity and the role of cyclins
within plants are comparatively less well documented.
Severa1 plant cyclin genes have nevertheless been characterized in various species such as Arabidopsis (Hemerly et
al., 1992) and maize (Renaudin et al., 1994).No related gene
has been isolated so far in tobacco; therefore, we focused
our attention on the isolation of cyclins from Nicotiana
tabacum to study cell-cycle regulation in this model plant
(Table I).
The 1656-bp fragment isolated from a tobacco cell-suspension cDNA library has been identified as a cyclin cDNA
with respect to its sequence similarity with other yeast,
animal, and plant cyclins yet characterized. This cDNA
sequence, named NTCYCl, contains an open reading frame
encoding a protein of 447 amino acids. The predicted primary sequence of the NTCYCl gene product shows regions
that are conserved among mitotic cyclins. The C terminus
contains a putative cyclin box between the amino acid
residues Met’” and Trp354,which is known to be involved
in binding to and activation of protein kinases of the CDK
family (Nugent et al., 1991).Also, the sequence from Met’”
to
within the cyclin box is similar to the P-box of
cyclin B. This consensus motif is necessary for the activation of the protein phosphatase cdc25 underlying activation of the cyclin B-~34‘~‘’ complex during the GJM
phase transition (Zheng and Ruderman, 1993). Additional
conserved domains are found in the N-terminal part of the
sequence outside the cyclin box. The motif RXXLXXXXN
specifies the destruction box well characterized in mitotic
cyclins. This acts as a signal for the degradation of cyclin at
the end of mitosis (Nugent et al., 1991).
The mechanism whereby the NTCYCl cyclin might regd a t e kinase activity during cell division in tobacco is not
Table 1. Characteristics of a 1656-bp cyclin cDNA sequence from
tobacco
Organism:
Nicotiana tabacum cv Xanthi; cell suspension.
Location of Cene:
Nuclear genome, chromosome location undetermined.
Function:
Encodes a cyclin named NTCYC1.
Techniques:
Cell-suspension cDNA library constructed in AZAPll (Stratagene), dideoxy nucleotide sequencing on both strands.
Method of lsolation and Identification:
Two degenerate primers, 5’-CTNMMNATYATNCAYMCNTTYYT-3 ’ and 5 ’-CCNC NRTANATYTCYTCRTAYTT-3’, corresponding to the conserved regions of known cyclin homologs
within the cyclin boxes were used to amplify a 113-bp PCR
fragment from a cDNA obtained by reverse transcription on
vegetative bud total RNA. This was subcloned in the Smal
site of pUC18, confirmed by sequencing, and used as a
probe to screen a cell-suspension cDNA library.
presently understood. Animal cells contain at least two
classes of mitotic cyclins, the A type and B type, distinct on
the basis of their respective consensus sequences. Cyclins A
and B have different mitotic functions and are degraded at
different times. However, the NTCYCl gene product cannot be assigned unequivocally as A or B type because
consensus sequences of both types are partially conserved
within NTCYCl. In the cyclin box region, the tobacco cyclin shares 41% sequence identity with the human cyclins
of both A and B types. According to Renaudin et al. (1994),
plant mitotic cyclins can be more easily classified into three
distinct groups conserved among monocotyledonous and
dicotyledonous species. Based on amino acid comparison,
the homology of up to 46% between the entire primary
sequences of NTCYCl and the maize cyclin CycIbZm suggests that the tobacco protein is more closely related to
plant cyclins of group I.
We are interested in how the expression of the cyclin
NTCYCl and other cyclins is regulated during cell division
in tobacco to elucidate the cell-cycle molecular machinery.
N . tabacum represents one of the plant model systems offering alternative ways to study cell division and its control
* Corresponding author; e-mail lrichard8ccr.jussieu.fr; fax 331-69 -33- 64 -23.
Abbreviation: CDK, cyclin-dependent kinase.
425
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426
Qin et al.
by phytohormones. These include protoplast cultures and
cell suspensions that can be synchronized during cell-cycle
progression (Nagata et al., 1992). &o, epidermal tobacco
tissues may be confined in vitro to produce, selectively,
flowers, vegetative buds, roots, or calli in response to exogenous phytohormones (Tran Thanh Van, 1973). Such
organogenic potentiality may be used to elucidate the role
of cyclins and other cell-cycle regulators during developmental processes.
Received October 7, 1994; accepted November 7, 1994.
Copyright Clearance Center: 0032-0889/95/108/0425/02.
The EMBL accession number for the sequence reported in this
article is 237978.
LITERATURE ClTED
Hemerly A, Bergounioux C, Van Montagu M, Inzé D, Ferreira P
(1992)Gene regulating the plant cell cycle: isolation of a mitotic-
Plant Physiol. Vol. 108, 1995
like cyclin from Arubidopsis thaliunu. Proc Natl Acad Sci USA 89:
3295-3299
Control Of the
'ycle. Dev Biol l53: l-I.5
Jacobs
Nagata T, Nemoto Y, Hasezawa S (1992) Tobacco BY-2 cell line as
the HeLa cell in the cell biology of higher plants. Int Rev Cytol
1 3 2 1-30
Nigg EA (1993) Targets of cyclin-dependent protein kinases. Curr
Opin Cell Biol 5 187-193
N'gent JHAr
Tr HJ'ams Js
Conserved
structural motifs in cyclins identified by sequence analysis. J Cell
Sci 99: 669474
Renaudin J-P, Colasanti J, Rime H, Yuan Z, Sundaresan V (1994)
Cloning of four cyclins from maize indicates that higher plants
have structurally distinct groups of mitotic cyclins. Proc Natl
Acad Sci USA 91: 7375-7379
Tran Thanh Van M (1973)In vitro control de novo flower, bud, root
and callus differentiation from excised epidermal tissues. Nature 246 44-45
Zheng X-F,Ruderman JV (1993) Functional analysis of the P box,
a domain in cyclin B required for the activation of cdc25. Cell75
155-164
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Copyright © 1995 American Society of Plant Biologists. All rights reserved.