ISOLATION OF A FULL-LENGTH MITOTIC CYCLIN CDNA CLONE CYCIIIMS FROM MEDICAGO-SATIVA - CHROMOSOMAL MAPPING AND EXPRESSION

Cyclins in association with the protein kinase p34(cdc2) and related c yclin-dependent protein kinases (cdks) are key regulatory elements in controlling the cell division cycle. Here, we describe the identificat ion and characterization of a full-length cDNA. clone of alfalfa mitot ic cyclin, termed CycIIIMs. Computer analysis of known plant cyclin ge ne sequences revealed that this cyclin belongs to the same;structural group as the other known partial alfalfa cyclin sequences. Genetic seg regation analysis based on DNA-DNA hybridization data showed that the CycIIIMs gene(s) locates in a single chromosomal region on linkage gro up 5 of the alfalfa genetic map between RFLP markers UO89A and CG13. T he assignment of this cyclin to the mitotic cyclin class was based on its cDNA-derived sequence and its differential expression during G2/M cell cycle phase transition of a partially synchronized alfalfa cell c ulture. Sequence analysis indicated common motifs with both the A- and B-types of mitotic cyclins similarly to the newly described B3-type o f animal cyclins.