Background: Entry into mitosis is regulated by cyclin dependent kinases that in turn are phosphoregulated. Inmost eukaryotes, phosphoregulation is through WEE1 kinase and CDC25 phosphatase. In higher plants ahomologous CDC25 gene is unconfirmed and hence the mitotic inducer Schizosaccharomyces pombe (Sp) cdc25has been used as a tool in transgenic plants to probe cell cycle function. Expression of Spcdc25 in tobacco BY-2cells accelerates entry into mitosis and depletes cytokinins; in whole plants it stimulates lateral root production.Here we show, for the first time, that alterations to cytokinin and ethylene signaling explain the rooting phenotypeelicited by Spcdc25 expression in Arabidopsis.Results: Expressing Spcdc25 in Arabidopsis results in increased formation of lateral and adventitious roots, areduction of primary root width and more isodiametric cells in the root apical meristem (RAM) compared withwild type. Furthermore it stimulates root morphogenesis from hypocotyls when cultured on two way grids ofincreasing auxin and cytokinin concentrations. Microarray analysis of seedling roots expressing Spcdc25 revealsthat expression of 167 genes is changed by > 2-fold. As well as genes related to stress responses and defence,these include 19 genes related to transcriptional regulation and signaling. Amongst these was the up-regulationof genes associated with ethylene synthesis and signaling. Seedlings expressing Spcdc25 produced 2-fold moreethylene than WT and exhibited a significant reduction in hypocotyl length both in darkness or when exposedto 10 ppm ethylene. Furthermore in Spcdc25 expressing plants, the cytokinin receptor AHK3 was downregulated,and endogenous levels of iPA were reduced whereas endogeous IAA concentrations in the rootsincreased.Conclusions: We suggest that the reduction in root width and change to a more isodiametric cell phenotype inthe RAM in Spcdc25 expressing plants is a response to ethylene over-production. The increased rooting phenotypein Spcdc25 expressing plants is due to an increase in the ratio of endogenous auxin to cytokinin that is known tostimulate an increased rate of lateral root production. Overall, our data reveal important cross talk between celldivision and plant growth regulators leading to developmental changes.
Perturbation of cytokinin and ethylene-signalling pathways explain the strong rooting phenotype exhibited by Arabidopsis expressing the Schizosaccharomyces pombe mitotic inducer, cdc25
Bruno L.;Bitonti M. B.;
2012-01-01
Abstract
Background: Entry into mitosis is regulated by cyclin dependent kinases that in turn are phosphoregulated. Inmost eukaryotes, phosphoregulation is through WEE1 kinase and CDC25 phosphatase. In higher plants ahomologous CDC25 gene is unconfirmed and hence the mitotic inducer Schizosaccharomyces pombe (Sp) cdc25has been used as a tool in transgenic plants to probe cell cycle function. Expression of Spcdc25 in tobacco BY-2cells accelerates entry into mitosis and depletes cytokinins; in whole plants it stimulates lateral root production.Here we show, for the first time, that alterations to cytokinin and ethylene signaling explain the rooting phenotypeelicited by Spcdc25 expression in Arabidopsis.Results: Expressing Spcdc25 in Arabidopsis results in increased formation of lateral and adventitious roots, areduction of primary root width and more isodiametric cells in the root apical meristem (RAM) compared withwild type. Furthermore it stimulates root morphogenesis from hypocotyls when cultured on two way grids ofincreasing auxin and cytokinin concentrations. Microarray analysis of seedling roots expressing Spcdc25 revealsthat expression of 167 genes is changed by > 2-fold. As well as genes related to stress responses and defence,these include 19 genes related to transcriptional regulation and signaling. Amongst these was the up-regulationof genes associated with ethylene synthesis and signaling. Seedlings expressing Spcdc25 produced 2-fold moreethylene than WT and exhibited a significant reduction in hypocotyl length both in darkness or when exposedto 10 ppm ethylene. Furthermore in Spcdc25 expressing plants, the cytokinin receptor AHK3 was downregulated,and endogenous levels of iPA were reduced whereas endogeous IAA concentrations in the rootsincreased.Conclusions: We suggest that the reduction in root width and change to a more isodiametric cell phenotype inthe RAM in Spcdc25 expressing plants is a response to ethylene over-production. The increased rooting phenotypein Spcdc25 expressing plants is due to an increase in the ratio of endogenous auxin to cytokinin that is known tostimulate an increased rate of lateral root production. Overall, our data reveal important cross talk between celldivision and plant growth regulators leading to developmental changes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
