Cytokinin metabolism in Physcomitrella patens: differences and similarities to higher plants

• Published in: Plant growth regulation 2003-02, Vol.39 (2), p.99-106
• Main Authors: VON SCHWARTZENBERG, Klaus, PETHE, Claude, LALOUE, Michel
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Growth regulators; Metabolism; Plant physiology and development
• ISSN: 0167-6903; 1573-5087
• DOI: 10.1023/A:1022576231875

Cytokinins play an important role in plant development and occur informs with different hormonal activity. As the nucleotide forms of cytokininsare considered to have little or no biological activity, the conversion ofcytokinin bases and ribosides to their nucleotides can contribute to the tuningof cytokinin activity in plant cells. Cytokinin metabolism was monitoredin vivo by feeding either radiolabelledisopentenyladenosine (^sup 3^H-[9R]iP) or isopentenyladenine(^sup 3^H-iP) to liquid grown chloronema tissue ofPhyscomitrellapatens (Hedw.) B.S.G. wild type. The riboside ^sup 3^H-[9R]iPwas rapidly converted to ^sup 3^H-iP, which was released into the culturemedium. The intracellular concentration of the ^sup 3^H-iP was twice ashigh as extracellular. From the overall amount of ^sup 3^H-iP about 95%were present in the medium. Cytokinin nucleotides occurred as tritiated mono-,di- and triphosphates of ^sup 3^H-[9R]iP. When feeding the base^sup 3^H-iP however, its main metabolic fate was degradation and nosignificant amounts of radiolabelled cytokinin nucleotides were detected. Forthe cytokinin metabolism in P. patens it is concludedthat,in contrast to higher plants nucleotides are mainly formed from ribosidesvia the adenosine kinase pathway and not byribophosphorylation of the cytokinin base via adeninephosphoribosyltransferase.[PUBLICATION ABSTRACT]