4/30/2023 0 Comments Airtool 1.7.22 crc errors![]() In this study, we revealed that enhancement of de novo biosynthesis is responsible for CK accumulation under elevated CO 2 and that the enhancement is triggered by sugars derived from photosynthesis. high carbon availability) remains to be determined. However, how CKs accumulate and whether the accumulation and root-to-shoot translocation of CK is relevant to growth acceleration under elevated CO 2 (i.e. In addition, an increase in tZ-type CKs was detected in the xylem sap of cotton and tobacco plants grown under elevated CO 2, implying that tZ-type CKs have a role as root-to-shoot signals under elevated CO 2 conditions 25, 39. CKs have been implicated in growth acceleration because cell division and cell differentiation in the meristem are influenced by CKs and are often accompanied by CK accumulation 26, 38. high carbon availability) generally results in growth acceleration of both shoots and roots, although the root-to-shoot mass ratios are variable depending on species and environmental conditions 25, 26, 29, 34, 35, 36, 37. In various plant species, elevated CO 2 (i.e. To maximize fitness, long-distance communication is required for plants to balance the growth of photosynthesizing leaves and that of carbon consuming roots in response to carbon availability 6, 33. Regulation of CK activity is relevant to various plant developmental processes and environmental responses such as shoot apical meristem activity, branching, stress and nutritional responses 22, 23, 24, 25, 26, 27, 28.īecause plants are autotrophs that rely on photosynthesis to gain most of their building materials and energy, carbon availability is a major factor defining plant growth and development 29, 30, 31, 32. Shoot-to-root translocation of CK via phloem is critical for root vascular patterning, whereas root-to-shoot translocation via xylem mediated by ABCG14 regulates shoot growth and development. Recently, CK translocation via the vascular system was reported to also be important 19, 20, 21. Side-chain modification to form tZ-type CKs by cytochrome P450 monooxygenase CYP735A specifies CK activity toward shoot growth 17, 18. CK quantity is regulated mostly at the levels of de novo biosynthesis and degradation catalysed by adenosine phosphate-isopentenyltransferase (IPT) and CK oxidase/dehydrogenase (CKX), respectively 13, 14, 15, 16. CK activity is controlled at diverse levels, including CK quantity and modification. ![]() Naturally occurring CKs are mostly N 6-prenylated adenine derivatives N 6-(∆ 2-isopentenyl)adenine (iP), trans-zeatin (tZ) and their conjugates (iP-type and tZ-type CKs, respectively) are the major forms in Arabidopsis thaliana 10, 11, 12. Local as well as long-distance signalling between cells and organs via signalling molecules such as sugars and plant hormones are vital for this coordination 1, 2, 3, 4, 5, 6Ĭytokinins (CKs) are a class of plant hormones that play a central role in the regulation of numerous aspects of plant growth and development acting as local and long-distance signals 7, 8, 9, 10, 11. ![]() Because multicellular higher plants consist of organs with different functions, for example photosynthesizing leaves and roots that absorb water and inorganic nutrients, the responses must be coordinated at the whole plant level. 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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