Abstract
Inhibitors of cyclin-dependent kinases (ICKs) are key regulators of cyclin-dependent kinase activities and cell division. Herein, we identified eight ICKs in maize, which we named Zeama;ICKs (ZmICKs). Primary sequencing and phylogenetic analyses were used to divide the ZmICK family into two classes: group B and group C. Subcellular localization analysis of ZmICK:enhanced green fluorescent protein (eGFP) fusion constructs in tobacco leaf cells indicated that ZmICKs are principally nuclear. Co-localization analysis of the ZmICKs and maize A-type cyclin-dependent kinase (ZmCDKA) was also performed using enhanced green fluorescent protein (eGFP) and red fluorescent protein (RFP) fusion constructs. The ZmICKs and ZmCDKA co-localized in the nucleus. Semi-quantitative RT-PCR analysis of the ZmICKs showed that they were expressed at different levels in all tissues examined and shared similar expression patterns with cell cycle-related genes. Yeast two-hybrid and bimolecular fluorescence complementation assays showed that ZmICK1, ZmICK2, ZmICK3, and ZmICK4 interact with ZmCDKA1 and ZmCDKA3. Interestingly, ZmICK7 interacts with D-type cyclins. Transformed and expressed ZmCDKA1 and ZmICKs together in fission yeast revealed that ZmICK1, ZmICK3, and ZmICK4 can affect ZmCDKA1 function. Moreover, the C-group of ZmICKs could interact with ZmCDKA1 directly and affect ZmCDKA1 function, suggesting that C-group ZmICKs are important for cell division regulation.
Highlights
The development of plant organs is directly dependent on the frequency of cell division, the parameters of the cell cycle, and the number and size of the cells
In Arabidopsis, ICK1 can interact with CDKA;[1], CycD1, CycD2, and CycD3; deletion analysis indicated that the conserved C-terminal region of ICK1 is important for interaction with CDKA;[1], whereas a region upstream of the conserved C-terminus is important for interaction with D-type cyclins[5,20]
We report the identification of nine ZmICK genes in the maize genome; these genes encode 8 proteins, each containing a cyclin-dependent kinase inhibitor (CDI) region, and two of the identified genes possess similar gene structure, cDNA sequence, and protein sequence
Summary
The development of plant organs is directly dependent on the frequency of cell division, the parameters of the cell cycle, and the number and size of the cells. To control the cell cycle and cell division, plants must modulate the activity of cyclin-dependent kinases (CDKs) during development and coordinate this activity with nutritional, hormonal, and environmental signals. The first plant cyclin-dependent kinase inhibitor was cloned from Arabidopsis thaliana using a yeast two-hybrid system, which verified the interaction between ICK/KRP proteins and CDKs3. Previous studies have shown that the ICK/KRP proteins interact with the A-type CDKs through the conserved C-terminal region[5,19,20]. In Arabidopsis, ICK1 can interact with CDKA;[1], CycD1, CycD2, and CycD3; deletion analysis indicated that the conserved C-terminal region of ICK1 is important for interaction with CDKA;[1], whereas a region upstream of the conserved C-terminus is important for interaction with D-type cyclins[5,20]. Tomato, tobacco, and alfalfa, ICKs can associate with different proteins, such as D-type cyclins, A-type cyclins, and A-type CDKs10,11,13,22,23
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