Abstract
In higher plants, seed germination is followed by postgerminative growth. One of the key developmental events during postgerminative growth is cotyledon greening, which enables a seedling to establish photosynthetic capacity. The plant phytohormone abscisic acid (ABA) plays a vital role by inhibiting seed germination and postgerminative growth in response to dynamically changing internal and environmental cues. It has been shown that abscisic acid insensitive5 (ABI5), a basic leucine zipper transcription factor, is an important factor in the regulation of the ABA-mediated inhibitory effect on seed germination and postgerminative growth. Conversely, the phytohormone cytokinin has been proposed to promote seed germination by antagonizing the ABA-mediated inhibitory effect. However, the underpinning molecular mechanism of cytokinin-repressed ABA signaling is largely unknown. Here, we show that cytokinin specifically antagonizes ABA-mediated inhibition of cotyledon greening with minimal effects on seed germination in Arabidopsis (Arabidopsis thaliana). We found that the cytokinin-antagonized ABA effect is dependent on a functional cytokinin signaling pathway, mainly involved in the cytokinin receptor gene cytokinin response1/Arabidopsis histidine kinase4, downstream histidine phosphotransfer protein genes AHP2, AHP3, and AHP5, and a type B response regulator gene, ARR12, which genetically acts upstream of ABI5 to regulate cotyledon greening. Cytokinin has no apparent effect on the transcription of ABI5. However, cytokinin efficiently promotes the proteasomal degradation of ABI5 in a cytokinin signaling-dependent manner. These results define a genetic pathway through which cytokinin specifically induces the degradation of ABI5 protein, thereby antagonizing ABA-mediated inhibition of postgerminative growth.
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Claims 6
Claim · model-written summary
Cytokinin antagonized ABA inhibition of cotyledon greening.
- Taxon
- Arabidopsis
Arabidopsise0 - Treatment
- cytokinine0
- Outcome
- cotyledon greeninge0
- Direction
- antagonizese0
- Comparator
- ABA-mediated inhibitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinin specifically antagonizes ABA-mediated inhibition of cotyledon greening with minimal effects on seed germination in Arabidopsis (Arabidopsis thaliana).”
Claim · model-written summary
Cytokinin had minimal effects on seed germination.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- cytokinine0
- Outcome
- seed germinatione0
- Direction
- minimal effectse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinin specifically antagonizes ABA-mediated inhibition of cotyledon greening with minimal effects on seed germination in Arabidopsis (Arabidopsis thaliana).”
Claim · model-written summary
Antagonism of ABA by cytokinin depended on the cytokinin signaling pathway.
Not reportedTaxon
Verbatim
e0“the cytokinin-antagonized ABA effect is dependent on a functional cytokinin signaling pathway”
Claim · model-written summary
Cytokinin receptor and downstream signaling genes contributed to regulation of cotyledon greening upstream of ABI5.
- Taxon
- ArabidopsisArabidopsise0
- Gene
- ARR12e0
- Outcome
- cotyledon greeninge0
- Qualifier
- genetically acts upstream of ABI5e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cytokinin receptor gene cytokinin response1/Arabidopsis histidine kinase4, downstream histidine phosphotransfer protein genes AHP2, AHP3, and AHP5, and a type B response regulator gene, ARR12, which genetically acts upstream of ABI5 to regulate cotyledon greening.”
Claim · model-written summary
Cytokinin had no apparent effect on ABI5 transcription.
Not reportedTaxonComparator
Verbatim
e0“Cytokinin has no apparent effect on the transcription of ABI5.”
Claim · model-written summary
Cytokinin promoted proteasomal degradation of ABI5 through cytokinin signaling.
- Treatment
- cytokinine0
- Gene
- ABI5e0
- Outcome
- proteasomal degradation of ABI5e0
- Direction
- promotese0
- Qualifier
- cytokinin signaling-dependent mannere0
Not reportedTaxon
Verbatim
e0“cytokinin efficiently promotes the proteasomal degradation of ABI5 in a cytokinin signaling-dependent manner.”
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