J. Joubes et al., A new C-type cyclin-dependent kinase from tomato expressed in dividing tissues does not interact with mitotic and G1 cyclins, PLANT PHYSL, 126(4), 2001, pp. 1403-1415
Cyclin-dependent kinases (CDKs) form a conserved superfamily of eukaryotic
serine-threonine protein kinases whose activity requires the binding of a c
yclin protein. CDKs are involved in many aspects of cell biology and notabl
y in the regulation of the cell cycle. Three DNAs encoding a C-type CDK, an
d a member of each B-type CDK subfamily, were isolated from tomato (Lycopse
rsicon esculentum Mill.) and designated Lyces; CDKC;1 (accession no. AJ2949
03.), Lyces; CDKB1;1 (accession no. AJ297916), and Lyces;CDKB2;1 (accession
no, AJ297917). The predicted amino acid sequences displayed the characteri
stic PITAIRE (CDKC), PPTALRE (CDKB1), and PPTTLRE (CDKB2) motives in the cy
clin-binding domain, clearly identifying the type of CDK. The accumulation
of all transcripts was associated preferentially with dividing tissues in d
eveloping tomato fruit and vegetative organs. In contrast to that of CDKA a
nd CDKBs, the transcription pattern of Lyces;CDKC;1 was shown to be indepen
dent of hormone and sugar supply in tomato cell suspension cultures and exc
ised roots. This observation, together with the absence of a patchy express
ion profile in in situ hybridization experiments, suggests a non-cell cycle
regulation of Lyces;CDKC;I. Using a two-hybrid assay, we showed that Lyces
;CDKC;1 did not interact with mitotic and G1 cyclins. The role of plant CDK
Cs in the regulation of cell division and differentiation is discussed with
regard to the known function of their animal counterparts.