52:	B-type cyclin gene expression in Nicotiana tabacum.

Authors:	Leng, Mei (A)Collins, Glenn, B.(A)Chappell, Joe(A)
Affiliations:	(A): Plant Physiology / Biochemistry / Molecular Biology Program, University of Kentucky
Presenter:	Leng, Mei , mleng1@ukcc.uky.edu

B-type cyclins play a critical role in mitosis. They are synthesized and accumulate in between the late stage of S- and G2- phases of the cell cycle and form complexes with cyclin-dependent kinases, specifically CDK2. These complexes serve to regulate the cell's entry and exit from the M-phase. In the current study, we are investigating developmental arrest of axillary bud development and have hypothesized a role for B-type cyclins in controlling axillary bud growth. Our hypothesis furthermore predicts a differential expression of B-type cyclins as the principle means for controlling axillary bud mitosis. Both cDNA and genomic clones for a Nicotiana tabacum B-type cyclin have been extensively characterized. The cDNA clone has also been used to correlate cell proliferation with transient changes in the gene mRNA amounts. The cyclin gene promoter region has subsequently been fused to the GUS reporter gene, and the developmental, organ specific and spatial expression patterns of GUS activity are being examined in transgenic plants. Strong GUS expression has been observed in the apical meristem, root tips, lateral roots and very young leaf meristems. Promoter deletion analyses are also being used to identify cis-sequences important for the many spatial and temporal expression patterns.