Cell Cycle Regulation of Cyclin-Dependent Kinases in Tobacco Cultivar Bright Yellow-2 Cells

Abstract

Plants possess two major classes of cyclin-dependent kinases (CDK) with cyclin-binding motifs PSTAIRE (CDK-a) and PPTA/TLRE (CDK-b). Tobacco (Nicotiana tabacum L. cv Bright Yellow-2) cells are the most highly synchronizable plant culture, but no detailed analysis of CDK activities has been reported in this system. Here we describe isolation of new PPTALRE CDKs (Nicta;CdkB1) from Bright Yellow-2 cells and present detailed analysis of the mRNA, protein and kinase activity levels of CdkB1, and the PSTAIRE CDKA during the growth and cell cycles. CdkA and CdkB1 transcripts are more abundant in exponential than in stationary phase cells, but the two genes show strikingly different regulation during the cell cycle. CdkA mRNA and protein accumulate during G1 in cells re-entering the cell cycle, and immunoprecipitated histone H1 kinase activity increases at the G1/S boundary. Aphidicolin synchronized cells show the highest CDKA-associated histone H1 kinase activity during S-G2 phases, although CdkA mRNA and protein levels are not significantly regulated. In contrast, CdkB1 transcripts are present at very low levels until S phase and CDKB1 protein and kinase activity is almost undetectable in G1. CdkB1 mRNA accumulates through S until M phase and its associated kinase activity peaks at the G2/M boundary, confirming that transcription of PPTALRE CDKs is cell cycle regulated. We suggest that CDKA kinase activity likely plays roles at the G1/S phase boundary, during S phase, and at the G2/M phase transition, and that CDKB1 kinase activity is present only at G2/M.

Atypical E2F activity restrains APC/C CCS52A2 function obligatory for endocycle onset

“…Because E2Fe/DEL1 represses the CCS52A2 promoter, we hypothesize that its level must drop below a critical threshold to allow sufficient accumulation of CCS52A2 during late S and G 2 for cells to proceed from division to endoreduplication, a model suggested by the dynamic simulation of the cell cycle phase-dependent expression level of CCS52A2 during leaf development. The steady increase in CCS52A2 during late S and G 2 likely counteracts the mitotic cyclin-dependent kinase (CDK) activity that builds up during these cell cycle phases (32,33), eventually blocking the G 2 to M transition and thereby triggering endoreduplication.…”

PhyscomitrellaCyclin-Dependent Kinase A Links Cell Cycle Reactivation to Other Cellular Changes during Reprogramming of Leaf Cells

“…The Pp ICK/KRP transcript, after a small and transient increase, was strongly repressed by cutting ( Figure 2O), suggesting that Pp ICK/KRP plays a similar role to At ICK/KRP. Finally, during S-phase in flowering plants as well as in metazoans, expression of histone H4 is strongly upregulated (Osley, 1991;Sorrell et al, 2001;Menges et al, 2002). Therefore, as a marker for S-phase, we quantified levels of the P. patens histone H4 gene HFO ( Figure 2P).…”

A PSTAIRE CDK-like protein localizes in nuclei and cytoplasm of Physarum polycephalum and functions in the mitosis

“…cdc2/CDK1, CDK2 and CDK3 [20][21][22]. In plants, PSTAIRE CDKs have been identified in several species, such as Arabidopsis (CDC2a), maize (cdc2ZmA), rice (cdc2Os-1 and cdc2Os-2), alfalfa (cdc2MsA and cdc2-MsB) and Fucus [9,10]. In P. polycephalum, a lower plant often used as an experimental model, Ducommun et al detected cdc2-related activity (histone H1 kinase activity) [14], and Shipley and Sauer found a 34 kD cdc2 homolog by using a peptide antibody directed against a consensus conserved sequence near the N-terminal end of p34 cdc2 [15].…”

“…The best characterized plant CDK belongs to CDK A or PSTAIRE CDKs. PSTAIRE CDKs can partially rescue yeast cdc2/CDC28 mutations and are therefore supposed to be functional homologs of the yeast CDKs [3], and play important roles in cell cycle control [1,[5][6][7][8][9][10]. PSTAIRE CDKs are regulated at several levels, including its expression, differential subcellular localization, phosphorylation, protolysis, and interaction with regulatory proteins.…”

“…PSTAIRE CDKs are regulated at several levels, including its expression, differential subcellular localization, phosphorylation, protolysis, and interaction with regulatory proteins. Investigations upon the subcellular localization [11][12][13] and functions [7][8][9][10] of PSTAIRE CDKs have been limited, and opinions on their subcellular location have been divergent [11][12][13].…”