Contrasting patterns of cytokinins between years in senescing aspen leaves

Cytokinins are plant hormones that typically block or delay leaf senescence. We profiled 34 different cytokinins/cytokinin metabolites (including precursors, conjugates and degradation products) in leaves of a free-growing mature aspen (Populus tremula) before and after the initiation of autumnal senescence over three consecutive years. The levels and profiles of individual cytokinin species, or classes/groups, varied greatly between years, despite the fact that the onset of autumn senescence was at the same time each year, and senescence was not associated with depletion of either active or total cytokinin levels. Levels of aromatic cytokinins (topolins) were low and changed little over the autumn period. Diurnal variations and weather-dependent variations in cytokinin content were relatively limited. We also followed the expression patterns of all aspen genes implicated as having roles in cytokinin metabolism or signaling, but neither the pattern of regulation of any group of genes nor the expression of any particular gene supported the notion that decreased cytokinin signaling could explain the onset of senescence. Based on the results from this tree, we therefore suggest that cytokinin depletion is unlikely to explain the onset of autumn leaf senescence in aspen.

Novak, OndrejSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skoglig genetik och växtfysiologi,Department of Forest Genetics and Plant Physiology,Palacký University Olomouc(Swepub:slu)48211 (author)
Karady, MichalSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skoglig genetik och växtfysiologi,Department of Forest Genetics and Plant Physiology(Swepub:slu)99348 (author)
Ljung, KarinSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skoglig genetik och växtfysiologi,Department of Forest Genetics and Plant Physiology(Swepub:slu)48434 (author)
Jansson, StefanUmeå universitet,Umeå Plant Science Centre (UPSC)(Swepub:umu)stja0001 (author)
Umeå universitetInstitutionen för fysiologisk botanik (creator_code:org_t)
Sveriges lantbruksuniversitet

By the author/editor: Edlund, Erik; Novak, Ondrej; Karady, Michal; Ljung, Karin; Jansson, Stefan

About the subject

AGRICULTURAL SCIENCES: AGRICULTURAL SCI ...; and Agricultural Bio ...; and Plant Biotechnol ...

By the university: Umeå University; Swedish University of Agricultural Sciences

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