Abstract
The CUP-SHAPED COTYLEDON (CUC) transcription factors control plant boundary formation, thus allowing the emergence of novel growth axes. While the developmental roles of the CUC genes in different organs and across species are well characterized, upstream and downstream events that contribute to their function are still poorly understood. To identify new players in this network, we performed a suppressor screen of CUC2g-m4, a line overexpressing CUC2 that has highly serrated leaves. We identified a mutation that simplifies leaf shape and affects MURUS1 (MUR1), which is responsible for GDP-L-fucose production. Using detailed morphometric analysis, we show that GDP-L-fucose has an essential role in leaf shape acquisition by sustaining differential growth at the leaf margins. Accordingly, reduced CUC2 expression levels are observed in mur1 leaves. Furthermore, genetic analyses reveal a conserved role for GDP-L-fucose in different developmental contexts where it contributes to organ separation in the same pathway as CUC2. Taken together, our results reveal that GDP-L-fucose is necessary for proper establishment of boundary domains in various developmental contexts.
Highlights
In multicellular organisms, the development of distinct organs often requires the establishment of boundaries to individualize functional units
Using genetic approaches coupled with detailed morphometric analyses, we show that MURUS1 (MUR1), which encodes a GDP-D-mannose 4,6-dehydratase involved in GDP-L-fucose production, is required for leaf shape development and more generally for boundary definition in plants
Mur1-1 plants grown in vitro in standard growth medium had smoother leaves than the wild type, while mur1-1 plants grown in medium supplemented with 10 mM L-fucose developed leaf serrations like the wild type (Fig. 3E and Supplementary Fig. 4); these results show that L-fucose itself is required for proper leaf serration in mur1 mutants, which are deficient in GDP-L-fucose biosynthesis
Summary
The development of distinct organs often requires the establishment of boundaries to individualize functional units. Several transcriptional regulators are involved in the development of boundaries in plants, including the CUPSHAPED COTYLEDON (CUC) transcription factors (reviewed in Žádníková and Simon, 2014; Hepworth and Pautot, 2015; Maugarny et al, 2015). They belong to the NAC (NO APICAL MERISTEM/ATAF1-2/CUC2) family, an evolutionarily conserved family of plant transcription factors notably involved in developmental processes and stress responses (Nuruzzaman et al, 2013). As players involved in boundary definition, CUC transcription factors are major regulators of plant architecture, controlling both shoot meristem maintenance (Aida et al, 1999) and correct organ separation in various developmental contexts
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