Maize cytokinin oxidase genes: differential expression and cloning of two new cDNAs.
Cytokinin oxidases (CKOs) play a major role in the regulation of hormone levels in plants by irreversibly degrading cytokinins. Two new cDNAs from maize (CKO2 and CKO3) were cloned and CKO activity of a recombinant CKO3 enzyme was demonstrated. CKO2 and CKO3 encode flavoproteins with 93% identity among each other compared with 45% identity with CKO1. The respective genes were mapped to BIN 3.05/06 and BIN 8.06 which belong to duplicated regions of the maize genome. For a better understanding of the role of CKO2 and CKO3 in maize development, their expression profiles were analysed in different organs and during kernel development via semi-quantitative RT-PCR. Different spatial and temporal expression patterns were observed for the two genes, as well as for CKO1 and two additional genes CKO4 and CKO5. CKO2 to CKO5 genes were mainly expressed in vegetative tissues, with unique expression patterns. CKO1 was most strongly expressed in the kernel. All five genes were expressed at early stages of kernel development, a period when a peak in cytokinin levels and a high cell division rate in the endosperm have been described. However, each gene had its own expression profile with a major difference concerning the onset of expression.
RDP, UMR 5667 INRA-CNRS-ENSL-UCBL, IFR128 BioSciences Lyon-Gerland, ENS-Lyon, 46 Allée d'Italie, F-69364 Lyon Cedex 07, France.
Agnès
A
Massonneau
Nicole
N
Houba-Hérin
Claude
C
Pethe
Catherine
C
Madzak
Matthieu
M
Falque
Mathieu
M
Mercy
David
D
Kopecny
Amel
A
Majira
Peter
P
Rogowsky
Michel
M
Laloue
D018076:DNA, Complementary / Q000032:analysis; D015870:Gene Expression; D017343:Genes, Plant; D030781:Organisms, Genetically Modified; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D025062:Yarrowia / Q000235:genetics; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development
D018076:DNA, Complementary; D010088:Oxidoreductases; C019984:cytokinin oxidase