| The Arabidopsis solo dancers (sds ) mutant is sterile and defective in pollen production. Phenotypic characterization indicated that the SDS gene is required for normal synapsis, bivalent formation, and recombination in meiosis. Sequence analysis suggested that SDS encodes a putative cyclin. Considering that less information is known about plant cyclins than animal cyclins, I and collaborators first performed BLAST searches of available databases to obtain sequences of all cyclin genes in Arabidopis and in other vascular plants. We then defined ten classes of plant cyclins based on phylogenetic analyses. Expression analyses also showed that Arabidopsis cyclins exhibit diverse expression patterns at the tissue level. The results suggest that plants possess a larger and more complex family of cyclins than animals. To provide further evidence for SDS as a cyclin gene and characterize different SDS protein domains, I generated six different SDS truncations and studied them in the budding yeast. It was found that SDS can rescue a yeast G1 cyclin deficient mutant and can interfere with the mitotic cell cycle in wild type yeast. Comparative studies of the SDS truncations also suggested that a portion of the N-terminal region upstream of the cyclin domain is required for SDS function in the yeast system. Further study of the full-length SDS and an SDS truncation, SDS201-578, in Arabidopsis showed that the SDS N-terminal region is required for the full activity of SDS. The meiotic phenotypes in the partially rescued sds meiocytes by SDS201-578 confirmed the requirement of SDS in synapsis. Sequence alignment of SDS homologs showed that there are several highly conserved motifs in their N-terminal regions, suggesting a possible involvement of these motifs in SDS function. |
