Regulation of plant growth by cytokinin

Werner, Tomáš; Motyka, Václav; Strnad, Miroslav; Schmülling, Thomas

doi:10.1073/pnas.171304098

Cited by 909 publications

(742 citation statements)

References 35 publications

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“…In a previous study, we showed that overexpression of AtCKX genes in transgenic tobacco plants reduces the endogenous cytokinin content and profoundly influences root and shoot development (Werner et al, 2001). Here, we report the functional analysis of six gene family members in the model plant Arabidopsis.…”

Section: Introductionmentioning

confidence: 85%

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Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Werner

Motyka

Laucou³

et al. 2003

Plant Cell

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Cytokinins are hormones that regulate cell division and development. As a result of a lack of specific mutants and biochemical tools, it has not been possible to study the consequences of cytokinin deficiency. Cytokinin-deficient plants are expected to yield information about processes in which cytokinins are limiting and that, therefore, they might regulate. We have engineered transgenic Arabidopsis plants that overexpress individually six different members of the cytokinin oxidase/dehydrogenase ( AtCKX ) gene family and have undertaken a detailed phenotypic analysis. Transgenic plants had increased cytokinin breakdown (30 to 45% of wild-type cytokinin content) and reduced expression of the cytokinin reporter gene ARR5 : GUS ( ␤ -glucuronidase). Cytokinin deficiency resulted in diminished activity of the vegetative and floral shoot apical meristems and leaf primordia, indicating an absolute requirement for the hormone. By contrast, cytokinins are negative regulators of root growth and lateral root formation. We show that the increased growth of the primary root is linked to an enhanced meristematic cell number, suggesting that cytokinins control the exit of cells from the root meristem. Different AtCKX-green fluorescent protein fusion proteins were localized to the vacuoles or the endoplasmic reticulum and possibly to the extracellular space, indicating that subcellular compartmentation plays an important role in cytokinin biology. Analyses of promoter: GUS fusion genes showed differential expression of AtCKX genes during plant development, the activity being confined predominantly to zones of active growth. Our results are consistent with the hypothesis that cytokinins have central, but opposite, regulatory functions in root and shoot meristems and indicate that a fine-tuned control of catabolism plays an important role in ensuring the proper regulation of cytokinin functions.

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Section: Introductionmentioning

confidence: 85%

“…Genes that encode enzymes that catalyze cytokinin breakdown have been isolated from maize (Houba-Hérin et al, 1999;Morris et al, 1999), Arabidopsis (Bilyeu et al, 2001;Werner et al, 2001), and orchids (Yang et al, 2003). The Arabidopsis AtCKX gene family has seven members ( AtCKX1 to AtCKX7 ) (for review, see Schmülling et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Werner

Motyka

Laucou³

et al. 2003

Plant Cell

Self Cite

1,265

1,209

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“…Cytokinins appear to interact with auxins antagonistically in a number of developmental processes such as to promote the release of axillary buds from dormancy and to suppress lateral root formation (Werner et al, 2001). They are synthesised in root tips (Chiappetta et al, 2001;Sossountov et al, 1988), and might be expected to limit the level of EXO expression in the meristem, since Northern analysis showed downregulation of EXO transcription by cytokinins.…”

Section: Regulation By Hormonesmentioning

confidence: 99%

EXORDIUM– a gene expressed in proliferating cells and with a role in meristem function, identified by promoter trapping in Arabidopsis

et al. 2003

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To identify new genes expressed in meristematic cells, a promoter trap insertional mutagenesis strategy was used in Arabidopsis thaliana. Transgenic line AtEM201 exhibits promoter trap GUS activity in embryos and in the regions of active cell division in the seedling, notably the apical meristems and young leaves. The tagged gene was named EXORDIUM (EXO). AtEM201 contains a single copy of the promoter trap T-DNA, located in the EXO gene promoter, resulting in a much reduced level of EXO transcription. Seedlings homozygous for the T-DNA insertion have no obvious mutant phenotype. The EXO gene, which forms part of a small gene family in Arabidopsis, is structurally related to the tobacco PHI-1 gene, which is re-activated in cultured cells following release from phosphate starvation-induced cell cycle arrest. Expression of both the EXO-GUS and the native EXO genes is downregulated by exogenous cytokinin. Expression studies using semisynchronised cells suggest that EXO mRNA is preferentially abundant during M phase of the cell cycle. Double mutant studies revealed that the exo mutation can suppress the defective root meristem phenotype of the hydra2 mutant, suggesting that EXO may be a component of a negative regulatory system for cell division.

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“…The use of synthetic cytokinins (BAP or TDZ) is advantageous not only because they promote shoot induction, but also because they are immune to degradation by cytokinin oxidase, thereby increasing the effectiveness of the pretreatment (Werner et al 2001). Reports on Curcuma longa and Curculigo orchioides show that explants obtained from seedlings germinated in the presence of TDZ are more responsive in shoot regeneration than explants with no treatment (Prathanturarug et al 2005, Thomas 2007).…”

Section: Cytokinin Pretreatment Relevancementioning

confidence: 99%

“…Finally, cytokinins play a central role during the cell cycle and influence numerous developmental processes, including the formation of shoot meristems, demonstrating their function beyond maintaining the cell cycle (Werner et al 2001).…”

Section: Cytokinin Pretreatment Relevancementioning

confidence: 99%