Abstract
Lateral branches such as shoot and panicle are determining factors and target traits for rice (Oryza sativa L.) yield improvement. Cytokinin promotes rice lateral branching; however, the mechanism underlying the fine-tuning of cytokinin homeostasis in rice branching remains largely unknown. Here, we report the map-based cloning of RICE LATERAL BRANCH (RLB) encoding a nuclear-localized, KNOX-type homeobox protein from a rice cytokinin-deficient mutant showing more tillers, sparser panicles, defected floret morphology as well as attenuated shoot regeneration from callus. RLB directly binds to the promoter and represses the transcription of OsCKX4, a cytokinin oxidase gene with high abundance in panicle branch meristem. OsCKX4 over-expression lines phenocopied rlb, which showed upregulated OsCKX4 levels. Meanwhile, RLB physically binds to Polycomb repressive complex 2 (PRC2) components OsEMF2b and co-localized with H3K27me3, a suppressing histone modification mediated by PRC2, in the OsCKX4 promoter. We proposed that RLB recruits PRC2 to the OsCKX4 promoter to epigenetically repress its transcription, which suppresses the catabolism of cytokinin, thereby promoting rice lateral branching. Moreover, antisense inhibition of OsCKX4 under the LOG promoter successfully increased panicle size and spikelet number per plant without affecting other major agronomic traits. This study provides insight into cytokinin homeostasis, lateral branching in plants, and also promising target genes for rice genetic improvement.
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Claims 10
Claim · model-written summary
The rlb cytokinin-deficient mutant shows more tillers.
- Taxon
- Oryza sativa
Oryza sativae0 - Material
- cytokinin-deficient mutante1
- Outcome
- tillerse1
- Direction
- moree1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e1“a rice cytokinin-deficient mutant showing more tillers, sparser panicles”
Claim · model-written summary
The rlb cytokinin-deficient mutant shows sparser panicles.
- Taxon
- Oryza sativaOryza sativae0
- Material
- cytokinin-deficient mutante1
- Outcome
- paniclese1
- Direction
- sparsere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e1“a rice cytokinin-deficient mutant showing more tillers, sparser panicles”
Claim · model-written summary
RLB directly binds the OsCKX4 promoter and represses its transcription.
- Taxon
- Oryza sativaOryza sativae0
- Gene
- OsCKX4e3
- Outcome
- transcription of OsCKX4e3
- Direction
- repressese3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e3“RLB directly binds to the promoter and represses the transcription of OsCKX4”
Claim · model-written summary
OsCKX4 over-expression lines phenocopied rlb and showed upregulated OsCKX4 levels.
- Taxon
- Oryza sativaOryza sativae0
- Treatment
- OsCKX4 over-expressione4
- Gene
- OsCKX4e4
- Outcome
- OsCKX4 levelse4
- Direction
- upregulatede4
- Comparator
- rlbe4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e4“OsCKX4 over-expression lines phenocopied rlb, which showed upregulated OsCKX4 levels”
Claim · model-written summary
RLB physically binds the PRC2 components OsEMF2b.
- Taxon
- Oryza sativaOryza sativae0
- Gene
- OsEMF2be5
- Outcome
- physically bindse5
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e5“RLB physically binds to Polycomb repressive complex 2 (PRC2) components OsEMF2b”
Claim · model-written summary
RLB co-localized with H3K27me3 in the OsCKX4 promoter.
- Taxon
- Oryza sativaOryza sativae0
- Gene
- OsCKX4e6
- Outcome
- co-localized with H3K27me3e6
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e6“co-localized with H3K27me3, a suppressing histone modification mediated by PRC2, in the OsCKX4 promoter”
Claim · model-written summary
RLB is proposed to recruit PRC2 to the OsCKX4 promoter to repress its transcription and so promote lateral branching.
- Taxon
- Oryza sativaOryza sativae0
- Gene
- OsCKX4e7
- Outcome
- lateral branchinge7
- Qualifier
- RLB recruits PRC2 to the OsCKX4 promoter to epigenetically repress its transcriptione7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e7“We proposed that RLB recruits PRC2 to the OsCKX4 promoter to epigenetically repress its transcription, which suppresses the catabolism of cytokinin, thereby promoting rice lateral branching”
Claim · model-written summary
Antisense inhibition of OsCKX4 under the LOG promoter increased panicle size.
- Taxon
- Oryza sativaOryza sativae0
- Treatment
- antisense inhibition of OsCKX4 under the LOG promotere1
- Outcome
- panicle sizee1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e1“antisense inhibition of OsCKX4 under the LOG promoter successfully increased panicle size and spikelet number per plant without affecting other major agronomic traits”
Claim · model-written summary
Antisense inhibition of OsCKX4 under the LOG promoter increased spikelet number per plant.
- Taxon
- Oryza sativaOryza sativae0
- Treatment
- antisense inhibition of OsCKX4 under the LOG promotere1
- Outcome
- spikelet number per plante1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e1“antisense inhibition of OsCKX4 under the LOG promoter successfully increased panicle size and spikelet number per plant without affecting other major agronomic traits”
Claim · model-written summary
Antisense inhibition of OsCKX4 under the LOG promoter did not affect other major agronomic traits.
- Taxon
- Oryza sativaOryza sativae0
- Treatment
- antisense inhibition of OsCKX4 under the LOG promotere1
- Outcome
- other major agronomic traitse1
- Direction
- without affectinge1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.)”
e1“antisense inhibition of OsCKX4 under the LOG promoter successfully increased panicle size and spikelet number per plant without affecting other major agronomic traits”
The same questions in other papers
loss of function · yield · Oryza sativa (rice)Positive and negative results
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