Cytokinin Regulates the Activity of Reproductive Meristems, Flower Organ Size, Ovule Formation, and Thus Seed Yield in Arabidopsis thaliana[C][W][OA]

By Isabel Bartrina, Elisabeth Otto, Miroslav Strnad, T. Werner, T. Schmülling. The Plant Cell, 2011

655 citations recorded by the source corpus.

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.

Subfields: Molecular Biology, Plant Science

View Paper: https://www.semanticscholar.org/paper/22ae939f80c8e14f8b2dd543445a08ca747a6440

How researchers see this paper

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In Molecular Biology

1. Jen Sheen
2. G. Schaller
3. J. Kieber
4. Ildoo Hwang
5. Bruno Müller
6. Xiansheng Zhang
7. Yu-Bo Liu
8. Y. Su

In Plant Science

1. Jen Sheen
2. G. Schaller
3. J. Kieber
4. Ildoo Hwang
5. Bruno Müller
6. Xiansheng Zhang
7. Yu-Bo Liu
8. Y. Su

Citations in the corpus

• Cytokinin signaling networks. (2012, background): “In addition, cytokinins induce WUS expression via AHK2 and AHK4 but repress CLV1, which encodes a receptor kinase for CLV3 peptide signaling to suppress WUS expression in the shoot apical meristem (9, 40).”
• Comprehending crystalline β-carotene accumulation by comparing engineered cell models and the natural carotenoid-rich system of citrus (2011, neutral): “Mutations in the CKX3 and CKX5 genes, which encode cytokinin oxidase/dehydrogenase enzymes functioning in degradation of this hormone, lead to increased proliferation in the placenta, supernumerary ovules, and increased seed set (Bartrina et al., 2011), suggesting that levels of cytokinin are import”
• Cytokinin signaling in plant development (2018, background): “Increases in cytokinin levels, in response to reduced expression of a CKX gene, have been linked to increases in grain yield in indica rice varieties (Ashikari et al., 2005), and the disruption of CKX genes in Arabidopsis leads to increased seed yield (Bartrina et al., 2011).”