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Cytokinin oxidase PpCKX1 plays regulatory roles in development and enhances dehydration and salt tolerance in Physcomitrella patens


Key message

PpCKX1 localizes to vacuoles and is dominantly expressed in the stem cells. PpCKX1 regulates developmental changes with increased growth of the rhizoid and enhances dehydration and salt tolerance.


Cytokinins (CKs) are plant hormones that regulate plant development as well as many physiological processes, such as cell division, leaf senescence, control of shoot/root ratio, and reproductive competence. Cytokinin oxidases/dehydrogenases (CKXs) control CK concentrations by degradation, and thereby influence plant growth and development. In the moss Physcomitrella patens, an evolutionarily early divergent plant, we identified six putative CKXs that, by phylogenetic analysis, form a monophyletic clade. We also observed that ProPpCKX1:GUS is expressed specifically in the stem cells and surrounding cells and that CKX1 localizes to vacuoles, as indicated by Pro35S:PpCKX1-smGFP. Under normal growth conditions, overexpression of PpCKX1 caused many phenotypic changes at different developmental stages, and we suspected that increased growth of the rhizoid could affect those changes. In addition, we present evidence that the PpCKX1-overexpressor plants show enhanced dehydration and salt stress tolerance. Taken together, we suggest that PpCKX1 plays regulatory roles in development and adaptation to abiotic stresses in this evolutionarily early land plant species.

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N-(3-Triethylammoniumpropyl)-4-(6-(4-(diethylamino) phenyl) hexatrienyl pyridinium dibromide




Physcomitrella patens Cytokinin oxidase


Quantitative real time-PCR




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We thank the Korea Basic Science Institute (Seoul) for helping with cytokinin analysis with HPLC-MS/MS. This research was supported by two grants (PJ011065 and PJ01367001) from the Next-Generation BioGreen 21 Program funded by the Rural Development Administration, Republic of Korea. This work was also partially supported by Korea University.

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Correspondence to Jeong Sheop Shin.

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Communicated by Youn-Il Park.

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Hyoung, S., Cho, S.H., Chung, J.H. et al. Cytokinin oxidase PpCKX1 plays regulatory roles in development and enhances dehydration and salt tolerance in Physcomitrella patens. Plant Cell Rep 39, 419–430 (2020).

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  • Abiotic stress tolerance
  • Cytokinin oxidase
  • Development
  • Evolution
  • Hormone
  • Physcomitrella patens