The Stem Cell Population of Arabidopsis Shoot Meristems Is Maintained by a Regulatory Loop between the CLAVATA and WUSCHEL Genes

Schoof, Heiko; Lenhard, Michael; Haecker, Achim; Mayer, Klaus; Jürgens, Gerd; Laux, Thomas

doi:10.1016/s0092-8674(00)80700-x

Cited by 1,519 publications

(1,527 citation statements)

References 24 publications

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“…Endogenous pigments were destained with 70% ethanol, and the GUS staining pattern was recorded with a stereomicroscope (SZX12; Olympus, Tokyo, Japan) or a microscope (Axioskop 2 plus; Zeiss, Jena, Germany) equipped with an Olympus C-4040ZOOM photographic device. For sectioning, plant tissue was fixed and embedded in LR White (Plano, Wetzlar, Germany) according to Schoof et al (2000), and 2.5-m thin sections were stained with 0.1% toluidine blue. Tissue for the observation of vasculature was cleared and visualized as described by Mattsson et al (1999).…”

Section: Gus Staining and Light Microscopymentioning

confidence: 99%

Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Werner

Motyka

Laucou³

et al. 2003

Plant Cell

1,305

1,243

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Cytokinins are hormones that regulate cell division and development. As a result of a lack of specific mutants and biochemical tools, it has not been possible to study the consequences of cytokinin deficiency. Cytokinin-deficient plants are expected to yield information about processes in which cytokinins are limiting and that, therefore, they might regulate. We have engineered transgenic Arabidopsis plants that overexpress individually six different members of the cytokinin oxidase/dehydrogenase ( AtCKX ) gene family and have undertaken a detailed phenotypic analysis. Transgenic plants had increased cytokinin breakdown (30 to 45% of wild-type cytokinin content) and reduced expression of the cytokinin reporter gene ARR5 : GUS ( ␤ -glucuronidase). Cytokinin deficiency resulted in diminished activity of the vegetative and floral shoot apical meristems and leaf primordia, indicating an absolute requirement for the hormone. By contrast, cytokinins are negative regulators of root growth and lateral root formation. We show that the increased growth of the primary root is linked to an enhanced meristematic cell number, suggesting that cytokinins control the exit of cells from the root meristem. Different AtCKX-green fluorescent protein fusion proteins were localized to the vacuoles or the endoplasmic reticulum and possibly to the extracellular space, indicating that subcellular compartmentation plays an important role in cytokinin biology. Analyses of promoter: GUS fusion genes showed differential expression of AtCKX genes during plant development, the activity being confined predominantly to zones of active growth. Our results are consistent with the hypothesis that cytokinins have central, but opposite, regulatory functions in root and shoot meristems and indicate that a fine-tuned control of catabolism plays an important role in ensuring the proper regulation of cytokinin functions.

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Section: Gus Staining and Light Microscopymentioning

confidence: 99%

Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Werner

Motyka

Laucou³

et al. 2003

Plant Cell

1,305

1,243

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“…In addition to specifying stamen and carpel identities, Arabidopsis AG controls floral determinacy by repressing the expression of WUS, a gene that maintains stem cell fates (Laux et al 1996;Schoof et al 2000;Lenhard et al 2001;Lohmann et al 2001;Baurle and Laux 2005;Kieffer et al 2006). To determine if the loss of floral determinacy in 35S∷AP2m3 lines could be due to reduced expression of NbAG, we identified NbAG and studied its mRNA levels by semi-quantitative RT-PCR (Fig.…”

Section: Arabidopsis Ap2 Induces Floral Patterning Defects In N Bentmentioning

confidence: 99%

Floral patterning defects induced by Arabidopsis APETALA2 and microRNA172 expression in Nicotiana benthamiana

et al. 2006

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Floral patterning and morphogenesis are controlled by many transcription factors including floral homeotic proteins, by which floral organ identity is determined. Recent studies have uncovered widespread regulation of transcription factors by microRNAs (miRNAs), ~21-nucleotide noncoding RNAs that regulate protein-coding RNAs through transcript cleavage and/or translational inhibition. The regulation of the floral homeotic gene APETALA2 (AP2) by miR172 is crucial for normal Arabidopsis flower development and is likely to be conserved across plant species. Here we probe the activity of the AP2/miR172 regulatory circuit in a heterologous Solanaceae species, Nicotiana benthamiana. We generated transgenic N. benthamiana lines expressing Arabidopsis wild type AP2 (35S∷AP2), miR172-resistant AP2 mutant (35S∷AP2m3) and MIR172a-1 (35S∷MIR172) under the control of the cauliflower mosaic virus 35S promoter. 35S∷AP2m3 plants accumulated high levels of AP2 mRNA and protein and exhibited floral patterning defects that included proliferation of numerous petals, stamens and carpels indicating loss of floral determinacy. On the other hand, nearly all 35S∷AP2 plants accumulated barely detectable levels of AP2 mRNA or protein and were essentially non-phenotypic. Overall, the data indicated that expression of the wild type Arabidopsis AP2 transgene was repressed at the mRNA level by an endogenous N. benthamiana miR172 homologue that could be detected using Arabidopsis miR172 probe. Interestingly, 35S∷MIR172 plants had sepal-to-petal transformations and/or more sepals and petals, suggesting interference with N. benthamiana normal floral homeotic gene function in perianth organs. Our studies uncover the potential utility of the Arabidopsis AP2/miR172 system as a tool for manipulation of floral architecture and flowering time in non-model plants.

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“…The WUSCHEL (WUS) is required for stem cell function in the SAM (Laux et al, 1996;Mayer et al, 1998). The CLA-VATA3 (CLV3) is involved in restricting stem cell population in the SAM by negatively regulating WUS (Brand et al, 2000;Schoof et al, 2000). The expression patterns of all these genes were therefore analyzed in 35S::CUC1 cotyledons by semiquantitative RT-PCR and in situ hybridization ( Figure 2).…”

Section: Ectopic Expression In 35s::cuc1 Seedlings Of Genes Involved mentioning

confidence: 99%

CUC1 gene activates the expression of SAM‐related genes to induce adventitious shoot formation

Hibara

Takada

Tasaka³

2003

The Plant Journal

177

138

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SummaryCUP-SHAPED COTYLEDON (CUC )1 encodes members of the NAC family. These are functionally redundant genes that are involved in shoot apical meristem (SAM) formation and cotyledon separation during embryogenesis in Arabidopsis. We analyzed transgenic plants overexpressing CUC1 (35S::CUC1 ). The cotyledons of these transgenic seedlings regularly had two basal lobes, small and round epidermal cells between the sinuses, and adventitious SAMs on the adaxial surface of this region. This suggests that CUC1 promotes adventitious SAM formation by maintaining epidermal cells in an undifferentiated state. In 35S::CUC1 cotyledons, the class I knotted-like homeobox (KNOX ) genes, including SHOOT MERISTEMLESS (STM ) and BREVIPEDICELLUS (BP ), which are involved in SAM formation and/or maintenance, were ectopically expressed before adventitious SAM formation. In stm mutants, ectopic expression of CUC1 could not induce adventitious SAMs, whereas they continued to be observed in bp mutants. These results suggest that STM, but not BP, is necessary for the formation of adventitious SAMs in 35S::CUC1 cotyledons. Furthermore, we examined the relationship between CUC1 and ASYMMETRIC LEAVES (AS )1 and AS2. The as1 and as2 mutations genetically enhance 35S::CUC1 phenotypes even in the absence of STM function. Interestingly, the as1 mutation can partially rescue the mutant vegetative development phenotypes in the cuc1 cuc2 double mutant. Our results suggest that CUC1 positively regulates SAM formation not only through STM but also through an STM-independent pathway that is negatively regulated by AS1 and AS2.

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The Stem Cell Population of Arabidopsis Shoot Meristems Is Maintained by a Regulatory Loop between the CLAVATA and WUSCHEL Genes

Cited by 1,519 publications

References 24 publications

Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Floral patterning defects induced by Arabidopsis APETALA2 and microRNA172 expression in Nicotiana benthamiana

CUC1 gene activates the expression of SAM‐related genes to induce adventitious shoot formation

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