Control of petal and pollen development by the plant cyclin-dependent kinase inhibitor ICK1 in transgenic Brassica plants.
The cyclin-dependent protein kinases (CDKs) have a central role in cell cycle regulation and can be inhibited by the binding of small protein CDK inhibitors. The first plant CDK inhibitor gene ICK1 was previously identified in Arabidopsis thaliana. In comparison to known animal CDK inhibitors, ICK1 protein exhibits unique structural and functional properties. The expression of ICK1 directed by the constitutive CaMV 35S promoter was shown to inhibit cell division and plant growth. The aim of this study was to determine the effects of ICK1 overexpression on particular organs and cells. ICK1 was expressed in specific tissues or cells of Brassica napus L. plants using two tissue-specific promoters, Arabidopsis AP3 and Brassica Bgp1. Transgenic AP3-ICK1 plants were morphologically normal except for some modified flowers either without petals or with petals of reduced size. Surprisingly, petals of novel shapes such as tubular petals were also observed, indicating a profound effect of cell division inhibition on morphogenesis. The cell size in the smaller modified petals was similar to that in control petals, suggesting that the reduction of petal size is mainly due to the reduction of cell numbers and that the inhibition of cell division does not necessarily lead to an increase in cell size. Transgenic Bgp1-ICK1 plants were normal morphologically; however, dramatic decreases in seed production were observed in some plants. In those plants, the ability of pollen to germinate and pollen nuclear number were affected. These results are discussed in relation to the cell cycle and plant development.
Zhou
Yongming
Y
Saskatoon Reseach Centre, 107 Science Place, Saskatoon, SK S7N 0X2, Canada.
Wang
Hong
H
Gilmer
Susan
S
Whitwill
Steve
S
Keller
Wilf
W
Fowke
Larry C
LC
D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D001937:Brassica / Q000235:genetics* / Q000254:growth & development; D018797:Cell Cycle Proteins / Q000235:genetics*; D002455:Cell Division / Q000235:genetics; D048429:Cell Size / Q000235:genetics; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D018506:Gene Expression Regulation, Plant; D026161:MADS Domain Proteins / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics; D018547:Plant Stems / Q000254:growth & development*; D030821:Plants, Genetically Modified; D011058:Pollen / Q000254:growth & development*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics
C101342:APETALA 3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; C114853:ICK1 protein, Arabidopsis; D026161:MADS Domain Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D018844:Cyclin-Dependent Kinases