We propose that plants employ a system to regulate growth in response to elevated CO 2 in which photosynthetically generated sugars induce de novo cytokinin biosynthesis for growth regulation.īeing sessile, plants integrate environmental and internal cues and regulate physiological and morphological processes accordingly to optimize growth and development. Cytokinin biosynthetic mutants were impaired in growth enhancement under elevated CO 2, demonstrating the involvement of de novo cytokinin biosynthesis for a robust growth response. Consistently, cytokinin precursor accumulation was enhanced by sugar supplements. The expression of these genes was inhibited by a photosynthesis inhibitor, DCMU, under elevated CO 2, and was enhanced by sugar supplements, indicating that photosynthetically generated sugars are responsible for the induction. In roots, elevated CO 2 induced two genes involved in de novo cytokinin biosynthesis: an adenosine phosphate-isopentenyltransferase gene, AtIPT3, and a cytochrome P450 monooxygenase gene, CYP735A2. Growing Arabidopsis seedlings under elevated CO 2 resulted in an accumulation of cytokinin precursors that preceded growth enhancement.
Here, we report that sugar-induced cytokinin biosynthesis plays a role in growth enhancement under elevated CO 2 in Arabidopsis thaliana. Cytokinins, plant hormones that play important roles in various aspects of growth and development, have been implicated in the carbon-dependent regulation of plant growth however, the details of their involvement remain to be elucidated. Carbon availability is a major regulatory factor in plant growth and development.
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