Plants in habitats with unpredictable conditions often have diversified bet-hedging strategies that ensure fitness over a wider range of variable environmental factors. A striking example is the diaspore (seed and fruit) heteromorphism that evolved to maximize species survival in Aethionema arabicum (Brassicaceae) in which external and endogenous triggers allow the production of two distinct diaspores on the same plant. Using this dimorphic diaspore model, we identified contrasting molecular, biophysical, and ecophysiological mechanisms in the germination responses to different temperatures of the mucilaginous seeds (M+ seed morphs), the dispersed indehiscent fruits (IND fruit morphs), and the bare non-mucilaginous M- seeds obtained by pericarp (fruit coat) removal from IND fruits. Large-scale comparative transcriptome and hormone analyses of M+ seeds, IND fruits, and M- seeds provided comprehensive datasets for their distinct thermal responses. Morph-specific differences in co-expressed gene modules in seeds, as well as in seed and pericarp hormone contents, identified a role of the IND pericarp in imposing coat dormancy by generating hypoxia affecting abscisic acid (ABA) sensitivity. This involved expression of morph-specific transcription factors, hypoxia response, and cell wall remodeling genes, as well as altered ABA metabolism, transport, and signaling. Parental temperature affected ABA contents and ABA-related gene expression and altered IND pericarp biomechanical properties. Elucidating the molecular framework underlying the diaspore heteromorphism can provide insight into developmental responses to globally changing temperatures.

• MeSH
• Brassicaceae * genetika   fyziologie   metabolismus   MeSH
• klíčení * genetika   fyziologie   MeSH
• kyselina abscisová metabolismus   MeSH
• ovoce * genetika   fyziologie   růst a vývoj   metabolismus   MeSH
• regulace genové exprese u rostlin * MeSH
• regulátory růstu rostlin metabolismus   MeSH
• semena rostlinná * genetika   fyziologie   růst a vývoj   metabolismus   MeSH
• teplota * MeSH
• transkriptom genetika   MeSH
• vegetační klid genetika   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kyselina abscisová MeSH
• regulátory růstu rostlin MeSH

The transition from germinating seeds to emerging seedlings is one of the most vulnerable plant life cycle stages. Heteromorphic diaspores (seed and fruit dispersal units) are an adaptive bet-hedging strategy to cope with spatiotemporally variable environments. While the roles and mechanisms of seedling traits have been studied in monomorphic species, which produce one type of diaspore, very little is known about seedlings in heteromorphic species. Using the dimorphic diaspore model Aethionema arabicum (Brassicaceae), we identified contrasting mechanisms in the germination responses to different temperatures of the mucilaginous seeds (M+ seed morphs), the dispersed indehiscent fruits (IND fruit morphs), and the bare non-mucilaginous M- seeds obtained from IND fruits by pericarp (fruit coat) removal. What follows the completion of germination is the pre-emergence seedling growth phase, which we investigated by comparative growth assays of early seedlings derived from the M+ seeds, bare M- seeds, and IND fruits. The dimorphic seedlings derived from M+ and M- seeds did not differ in their responses to ambient temperature and water potential. The phenotype of seedlings derived from IND fruits differed in that they had bent hypocotyls and their shoot and root growth was slower, but the biomechanical hypocotyl properties of 15-day-old seedlings did not differ between seedlings derived from germinated M+ seeds, M- seeds, or IND fruits. Comparison of the transcriptomes of the natural dimorphic diaspores, M+ seeds and IND fruits, identified 2,682 differentially expressed genes (DEGs) during late germination. During the subsequent 3 days of seedling pre-emergence growth, the number of DEGs was reduced 10-fold to 277 root DEGs and 16-fold to 164 shoot DEGs. Among the DEGs in early seedlings were hormonal regulators, in particular for auxin, ethylene, and gibberellins. Furthermore, DEGs were identified for water and ion transporters, nitrate transporter and assimilation enzymes, and cell wall remodeling protein genes encoding enzymes targeting xyloglucan and pectin. We conclude that the transcriptomes of seedlings derived from the dimorphic diaspores, M+ seeds and IND fruits, undergo transcriptional resetting during the post-germination pre-emergence growth transition phase from germinated diaspores to growing seedlings.

• Klíčová slova
• bet-hedging strategy, diaspore dimorphism, fruit and seed heteromorphism, pericarp-imposed dormancy, pre-emergence growth, seed seedling transition, seedling stress resilience, transcriptome resetting,
• Publikační typ
• časopisecké články MeSH

Developing innovative agri-technologies is essential for the sustainable intensification of global food production. Seed dormancy is an adaptive trait which defines the environmental conditions in which the seed is able to germinate. Dormancy release requires sensing and integration of multiple environmental signals, a complex process which may be mimicked by seed treatment technologies. Here, we reveal molecular mechanisms by which non-thermal (cold) atmospheric gas plasma-activated water (GPAW) releases the physiological seed dormancy of Arabidopsis thaliana. GPAW triggered dormancy release by synergistic interaction between plasma-generated reactive chemical species (NO3-, H2O2, ·NO, and ·OH) and multiple signalling pathways targeting gibberellin and abscisic acid (ABA) metabolism and the expression of downstream cell wall-remodelling genes. Direct chemical action of GPAW on cell walls resulted in premature biomechanical endosperm weakening. The germination responses of dormancy signalling (nlp8, prt6, and dog1) and ABA metabolism (cyp707a2) mutants varied with GPAW composition. GPAW removes seed dormancy blocks by triggering multiple molecular signalling pathways combined with direct chemical tissue weakening to permit seed germination. Gas plasma technologies therefore improve seed quality by mimicking permissive environments in which sensing and integration of multiple signals lead to dormancy release and germination.

• Klíčová slova
• Arabidopsis thaliana, Abscisic acid metabolism, endosperm weakening, gas plasma-activated water, nitrogen signalling, non-thermal atmospheric gas plasma technology, plant hormone signalling, reactive oxygen species, seed dormancy,
• MeSH
• Arabidopsis * metabolismus   MeSH
• klíčení fyziologie   MeSH
• kyselina abscisová metabolismus   MeSH
• peroxid vodíku metabolismus   MeSH
• proteiny huseníčku * metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• semena rostlinná metabolismus   MeSH
• technologie MeSH
• vegetační klid fyziologie   MeSH
• voda metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DOG1 protein, Arabidopsis MeSH Prohlížeč
• kyselina abscisová MeSH
• peroxid vodíku MeSH
• proteiny huseníčku * MeSH
• voda MeSH

Molecular responses of plants to natural phytotoxins comprise more general and compound-specific mechanisms. How phytotoxic chalcones and other flavonoids inhibit seedling growth was widely studied, but how they interfere with seed germination is largely unknown. The dihydrochalcone and putative allelochemical myrigalone A (MyA) inhibits seed germination and seedling growth. Transcriptome (RNAseq) and hormone analyses of Lepidium sativum seed responses to MyA were compared to other bioactive and inactive compounds. MyA treatment of imbibed seeds triggered the phased induction of a detoxification programme, altered gibberellin, cis-(+)-12-oxophytodienoic acid and jasmonate metabolism, and affected the expression of hormone transporter genes. The MyA-mediated inhibition involved interference with the antioxidant system, oxidative signalling, aquaporins and water uptake, but not uncoupling of oxidative phosphorylation or p-hydroxyphenylpyruvate dioxygenase expression/activity. MyA specifically affected the expression of auxin-related signalling genes, and various transporter genes, including for auxin transport (PIN7, ABCG37, ABCG4, WAT1). Responses to auxin-specific inhibitors further supported the conclusion that MyA interferes with auxin homeostasis during seed germination. Comparative analysis of MyA and other phytotoxins revealed differences in the specific regulatory mechanisms and auxin transporter genes targeted to interfere with auxin homestasis. We conclude that MyA exerts its phytotoxic activity by multiple auxin-dependent and independent molecular mechanisms.

• Klíčová slova
• ATP-binding cassette (ABC) transporter, PIN auxin efflux carrier, WRKY transcription factors, allelochemical and allelopathy, aquaporin-mediated water transport, auxin transport and homeostasis, cis-(+)-12-oxophytodienoic acid (OPDA) reductase, gibberellin metabolism, phytotoxin detoxification programme, seed germination,
• MeSH
• chalkonoidy MeSH
• homeostáza MeSH
• hormony metabolismus   MeSH
• klíčení * genetika   MeSH
• kyseliny indoloctové metabolismus   MeSH
• Lepidium sativum * metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   farmakologie   MeSH
• semena rostlinná genetika   MeSH
• semenáček metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chalkonoidy MeSH
• hormony MeSH
• kyseliny indoloctové MeSH
• myrigalone A MeSH Prohlížeč
• regulátory růstu rostlin MeSH

The dynamic behaviour of seeds in soil seed banks depends on their ability to act as sophisticated environmental sensors to adjust their sensitivity thresholds for germination by dormancy mechanisms. Here we show that prolonged incubation of sugar beet fruits at low temperature (chilling at 5°C, generally known to release seed dormancy of many species) can induce secondary nondeep physiological dormancy of an apparently nondormant crop species. The physiological and biophysical mechanisms underpinning this cold-induced secondary dormancy include the chilling-induced accumulation of abscisic acid in the seeds, a reduction in the embryo growth potential and a block in weakening of the endosperm covering the embryonic root. Transcriptome analysis revealed distinct gene expression patterns in the different temperature regimes and upon secondary dormancy induction and maintenance. The chilling caused reduced expression of cell wall remodelling protein genes required for embryo cell elongation growth and endosperm weakening, as well as increased expression of seed maturation genes, such as for late embryogenesis abundant proteins. A model integrating the hormonal signalling and master regulator expression with the temperature-control of seed dormancy and maturation programmes is proposed. The revealed mechanisms of the cold-induced secondary dormancy are important for climate-smart agriculture and food security.

• Klíčová slova
• coat dormancy, cold-induced dormancy, embryo growth potential, endosperm weakening, germination temperature, secondary dormancy, seed transcriptomes, sugar beet,
• MeSH
• Beta vulgaris * genetika   MeSH
• klíčení fyziologie   MeSH
• kyselina abscisová metabolismus   MeSH
• semena rostlinná fyziologie   MeSH
• vegetační klid genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyselina abscisová MeSH