A new D-type cyclin of Arabidopsis thaliana expressed during lateral root primordia formation

D-type cyclins are believed to regulate the onset of cell division upon mit ogenic signaling. Here, the isolation is reported of a new D-type cyclin ge ne (CYCD4;1) of Arabidopsis thaliana (L.) Heynh. during a two-hybrid screen using the cyclin-dependent kinase CDC2aAt as bait. Transcription of CYCD4; 1 can be induced by sucrose. The co-regulated expression of CYCD4;1 and CDC 2aAt in starved suspension cultures upon mitogenic stimulation indicates th at the formation of a complex between these two partners is important for t he resumption of cell division activity. By in-situ hybridizations CYCD4;1 was shown to be expressed during vascular tissue development, embryogenesis , and formation of lateral root primordia. Expression during: the latter pr ocess suggests that the induced expression of D-type cyclins by mitogenic s timuli might be one of the rate-limiting events for the initiation of later al roots.