Control of petal and pollen development by the plant cyclin-dependent kinase inhibitor ICK1 in transgenic Brassica plants

Abstract

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.

Multiple Functions of Kip-Related Protein5 Connect Endoreduplication and Cell Elongation

“…This result is in apparent contradiction to previously reported KRP overexpression studies (De Veylder et al, 2001;Jasinski et al, 2002;Zhou et al, 2002;Schnittger et al, 2003) but is in agreement with the observed stimulation of the endoreduplication cycle in weak KRP2 OE plants (Verkest et al, 2005). In addition, although KRP5 overexpression does not affect overall plant size, some results reported here suggest that KRP5 can negatively influence cell proliferation.…”

“…As demonstrated by their ability to inhibit CDK activity, plant KRP genes encode functional CKIs. Several reports have established that KRPs bind CDKs of the CDK A type and B type (Lui et al, 2000;De Veylder et al, 2001;Jasinski et al, 2002;Zhou et al, 2002), suggesting that they could all function at the G1/S transition and at the G2/M transition. Consistently, CDK complexes containing cyclin D or A can be inhibited by KRPs in vitro (Coelho et al, 2005), and overexpression of KRPs can restore the growth defects induced by D-type cyclin overexpression (Jasinski et al, 2002;Schnittger et al, 2003;Zhou et al, 2003).…”

Cyclin-Dependent Kinase Inhibitors in Maize Endosperm and Their Potential Role in Endoreduplication

“…However, the callus with the highest expression of Zeama;KRP;1 had the lowest percentage of endoreduplicated nuclei and there was no evidence of endoreduplication in calli expressing RepA only. Overexpression of the Zeama;KRPs by themselves severely reduced growth of embryonic maize calli, as was observed in several previous studies in which CKIs were constitutively expressed , Jasinski et al, 2002, Zhou et al, 2002a, 2002b.…”

“…Because of the sequence similarity between the plant and mammalian CKIs of the Cip/Kip family, it has been inferred based on indirect evidence that the plant KRPs inhibit CDK activity through interaction with cyclin/CDK complexes (Wang et al, 1998;De Veylder et al, 2001;Jasinski et al, 2002;Zhou et al, 2002aZhou et al, , 2002bSchnittger et al, 2003).…”

RAD5a and REV3 function in two alternative pathways of DNA-damage tolerance in Arabidopsis

“…Roots were removed from 9-day seedlings and the shoot part (almost entirely leaves) was used for flow cytometric analysis as described (Zhou et al, 2002). Briefly, fresh leaf tissue from mature Arabidopsis leaves was sampled in a 60-mm petri plate containing 400 µl of solution A of the High Resolution DNA kit-Type P (Partech, Munster, Germany).…”