Michel Laloue

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Cytokinins are degraded by cytokinin oxidases (CKOs) which catalyse cleavage of the N6-(isopent-2-enyl)-side chain resulting in formation of adenine-type compounds. CKO activity has been recorded in many plants and is thought to play a key role in controlling cytokinin levels in plants. Several partially purified CKOs have been characterised but no genes(More)
The uptake and metabolism of the cytokinin benzyl adenine (BA) was compared in two lines of Petunia hybrida Vilm. differing in their shoot organogenic response. Leaf transfer experiments using shoot induction medium containing 4.4 micromolar BA showed that leaf explants from petunia line St40 required a shoot induction period of 6 to 10 days for commitment(More)
As part of the study of the possible role(s) of CBF-1, a cytokinin-binding protein abundant in wheat embryo, a cytokinin oxidase was found in wheat (Triticum aestivum L.) germ and partially purified by conventional purification techniques and high performance chromatofocusing. This preparation catalyzes conversion of N(6)-(Delta(2)-isopentenyl)adenosine to(More)
Ove mutants in the moss Physcomitrella patens can arise from different recessive mutations. These mutants display a much larger number of buds than the wild type (wt) due to a dramatic overproduction of cytokinins (Cks), which are released into the culture medium (T.L. Wang, R. Horgan, D.J. Cove [1981] Plant Physiol 68: 735-738). The amounts of(More)
Cytokinin oxidase/dehydrogenase (CKO/CKX) is a flavoenzyme, which irreversibly inactivates cytokinins by severing the isoprenoid side chain from the adenine/adenosine moiety. There are several genes coding for the enzyme in maize (Zea mays). A Z. mays CKO1 cDNA was cloned in the yeast Yarrowia lipolytica to achieve heterologous protein expression. The(More)
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(More)
Adenine phosphoribosyltransferase (APRTase) is an important enzyme for its ability to convert adenine, a byproduct of many biochemical reactions, into AMP. By functional complementation of an Escherichia coli mutant, cDNAs encoding two APRTases have been cloned from Arabidopsis thaliana. One of the cDNAs (ATapt1) has been previously identified while the(More)
As in higher plants, the development of the moss Physcomitrella patens is regulated by environmental signals and phytohormones. At the protonema level transition from chloronema to caulonema cells is under auxin control. The formation on second sub-apical caulonema cells of buds that will give rise to the leafy gametophore requires cytokinins. Using(More)
Root hairs are a major site for the uptake of water and nutrients into plants, and they form an increasingly important model system for the study of development in higher plants. We now report on the molecular genetic analysis of the srh1 mutant in Arabidopsis thaliana impaired in root hair tip growth. We show that srh1 is a new allele of cow1 (can of(More)
Formation of the riboside-5'-monophosphate is a general feature of the metabolism of cytokinins in plants. As part of a study of the biological significance of the nucleotide form of cytokinins, we analyzed a mutant of Arabidopsis thaliana deficient in adenine phosphoribosyltransferase (APRT) activity for its ability to metabolize N(6)-benzyladenine (BA).(More)