In yeast and animals, cyclins have been demonstrated to be important regula
tors of cell, cycle progression. In recent years, a large number of A-, B-,
and D-class cyclins have been isolated from a variety of plant species. On
e class of cyclins, the D-class cyclins, is important for progression throu
gh G1 phase of the cell cycle. In Arabidopsis, four D-class cyclins have be
en isolated and characterized (CYCLIN-D1;1, CYCLIN-D2;1, CYCLIN-D3;1, and C
YCLIN-D4;1). In this report we describe the characterization of a fifth D-c
lass cyclin gene, CYCLIN-D3;2 (CYCD3;2), from Arabidopsis. An enhancer trap
line, Line 5580, contains a T-DNA insertion in CYCD3;2. Enhancer trap line
5580 exhibits expression in young vegetative and floral primordia. In Line
5580, T-DNA is inserted in the first exon of the CYCD3;2 gene; in homozygo
us 5580 plants CYCD3;2 RNA is not detectable. Even though CYCD3;2 gene func
tion is eliminated, homozygous 5580 plants do not exhibit an obvious growth
or developmental phenotype. Via in situ hybridization we demonstrate that
CYCD3;2 RNA is expressed in developing vegetative and floral primordia. In
addition, CYCD3;2 is also capable of rescuing a yeast strain that is defici
ent in G1 cyclin activity.