This work shows that the mutation of two cytokinin oxidase/dehydrogenases causes the formation of more and larger flowers and describes a previously undiscovered function of cytokinin in ovule-forming placenta tissue. Its findings support a central function of cytokinin in regulating reproductive meristems and highlight the relevance of sink strength in determining yield. The size and activity of the shoot apical meristem is regulated by transcription factors and low molecular mass signals, including the plant hormone cytokinin. The cytokinin status of the meristem depends on different factors, including metabolic degradation of the hormone, which is catalyzed by cytokinin oxidase/dehydrogenase (CKX) enzymes. Here, we show that CKX3 and CKX5 regulate the activity of the reproductive meristems of Arabidopsis thaliana. CKX3 is expressed in the central WUSCHEL (WUS) domain, while CKX5 shows a broader meristematic expression. ckx3 ckx5 double mutants form larger inflorescence and floral meristems. An increased size of the WUS domain and enhanced primordia formation indicate a dual function for cytokinin in defining the stem cell niche and delaying cellular differentiation. Consistent with this, mutation of a negative regulator gene of cytokinin signaling, ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6, which is expressed at the meristem flanks, caused a further delay of differentiation. Terminal cellular differentiation was also retarded in ckx3 ckx5 flowers, which formed more cells and became larger, corroborating the role of cytokinin in regulating flower organ size. Furthermore, higher activity of the ckx3 ckx5 placenta tissue established supernumerary ovules leading to an increased seed set per silique. Together, the results underpin the important role of cytokinin in reproductive development. The increased cytokinin content caused an ~55% increase in seed yield, highlighting the relevance of sink strength as a yield factor.
Cytokinin Regulates the Activity of Reproductive Meristems, Flower Organ Size, Ovule Formation, and Thus Seed Yield in Arabidopsis thaliana[C][W][OA]
Isabel Bartrina,Elisabeth Otto,M. Strnad,T. Werner,T. Schmülling
Published 2011 in The Plant Cell
ABSTRACT
PUBLICATION RECORD
- Publication year
2011
- Venue
The Plant Cell
- Publication date
2011-01-01
- Fields of study
Biology, Medicine, Environmental Science
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- ckx3 and ckx5
Two Arabidopsis cytokinin oxidase/dehydrogenase enzymes discussed as meristem-associated regulators of cytokinin levels.
Aliases: cytokinin oxidase/dehydrogenase 3 and 5, CKX3/CKX5
- ckx3 ckx5 double mutants
Arabidopsis plants carrying loss-of-function mutations in both CKX3 and CKX5.
Aliases: ckx3 ckx5 mutants
- cytokinin
A plant hormone that acts as a low-molecular-mass signal in meristem and flower development.
- flower organ size
The size of floral organs produced during flower development.
Aliases: floral organ size
- ovule-forming placenta tissue
The placenta tissue in the Arabidopsis flower where ovules initiate and develop.
Aliases: placenta tissue
- reproductive meristems
The inflorescence and floral meristems that generate reproductive structures in Arabidopsis.
Aliases: inflorescence meristems, floral meristems
- seed yield
The amount of seed produced as the output measure in siliques or whole plants.
Aliases: yield
- wuschel domain
The central meristematic domain characterized by WUS expression in Arabidopsis reproductive meristems.
Aliases: WUS domain
REFERENCES
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