The seed-to-seedling transition represents a key developmental and metabolic switch in plants. Catabolism of seed storage reserves fuels germination and early seedling emergence until photosynthesis is established. The seed-to-seedling developmental transition is controlled by Polycomb repressive complex 2 (PRC2). However, the coordination of PRC2 activity and its contribution to transcriptional reprogramming during seedling establishment remain unknown. By analyzing H3K27me3 re-distribution and changes in gene transcription in the shoot and root tissues of heterotrophic and photoautotrophic Arabidopsis (Arabidopsis thaliana) seedlings, we reveal 2 phases of PRC2-mediated gene repression. The first phase is independent of light and photosynthesis and results in the irreversible repression of the embryo maturation program, marked by heterotrophy and reserve storage molecule biosynthesis. The second phase is associated with the repression of metabolic pathways related to germination and early seedling emergence, and H3K27me3 deposition in this phase is sensitive to photosynthesis inhibition. We show that preventing the transcription of the PRC2-repressed glyoxylate cycle gene ISOCITRATE LYASE promotes the vegetative phase transition in PRC2-depleted plants. Our findings underscore a key role of PRC2-mediated transcriptional repression in the coordinated metabolic and developmental switches that occur during seedling emergence and emphasize the close connection between metabolic and developmental identities.

• MeSH
• Arabidopsis * genetika   metabolismus   růst a vývoj   fyziologie   MeSH
• autotrofní procesy MeSH
• fotosyntéza genetika   MeSH
• heterotrofní procesy genetika   MeSH
• histony metabolismus   MeSH
• klíčení genetika   MeSH
• PRC2 * metabolismus   genetika   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• regulace genové exprese u rostlin MeSH
• semena rostlinná genetika   růst a vývoj   metabolismus   MeSH
• semenáček * genetika   růst a vývoj   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• histony MeSH
• PRC2 * MeSH
• proteiny huseníčku * MeSH

BACKGROUND AND AIMS: The benefits and costs of amphistomy (AS) vs. hypostomy (HS) are not fully understood. Here, we quantify benefits of access of CO2 through stomata on the upper (adaxial) leaf surface, using 13C abundance in the adaxial and abaxial epicuticular wax. Additionally, a relationship between the distribution of stomata and epicuticular wax on the opposite leaf sides is studied. METHODS: We suggest that the 13C content of long-chain aliphatic compounds of cuticular wax records the leaf internal CO2 concentration in chloroplasts adjacent to the adaxial and abaxial epidermes. This unique property stems from: (1) wax synthesis being located exclusively in epidermal cells; and (2) ongoing wax renewal over the whole leaf lifespan. Compound-specific and bulk wax 13C abundance (δ) was related to amphistomy level (ASL; as a fraction of adaxial in all stomata) of four AS and five HS species grown under various levels of irradiance. The isotopic polarity of epicuticular wax, i.e. the difference in abaxial and adaxial δ (δab - δad), was used to calculate the leaf dorsiventral CO2 gradient. Leaf-side-specific epicuticular wax deposition (amphiwaxy level) was estimated and related to ASL. KEY RESULTS: In HS species, the CO2 concentration in the adaxial epidermis was lower than in the abaxial one, independently of light conditions. In AS leaves grown in high-light and low-light conditions, the isotopic polarity and CO2 gradient varied in parallel with ASL. The AS leaves grown in high-light conditions increased ASL compared with low light, and δab - δad approached near-zero values. Changes in ASL occurred concomitantly with changes in amphiwaxy level. CONCLUSIONS: Leaf wax isotopic polarity is a newly identified leaf trait, distinguishing between hypo- and amphistomatous species and indicating that increased ASL in sun-exposed AS leaves reduces the CO2 gradient across the leaf mesophyll. Stomata and epicuticular wax deposition follow similar leaf-side patterning.

• Klíčová slova
• Brassica oleracea, Capsicum annuum, Amphistomy, abaxial, adaxial, carbon isotope, cuticle, epicuticular wax, leaf internal CO2 concentration, light, photosynthesis, stomata,
• MeSH
• epidermis rostlin * metabolismus   MeSH
• fotosyntéza MeSH
• izotopy uhlíku * analýza   MeSH
• listy rostlin * metabolismus   MeSH
• oxid uhličitý * metabolismus   MeSH
• průduchy rostlin * fyziologie   MeSH
• vosky * metabolismus   chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Carbon-13 MeSH Prohlížeč
• izotopy uhlíku * MeSH
• oxid uhličitý * MeSH
• vosky * MeSH