Investigating the mechanisms underlying the early post-transplantation phase of Posidonia oceanica reveals tissue-specific molecular trajectories of acclimatisation during early seedling establishment and identifies candidate molecular indicators of field acclimatisation and thermal stress responses, providing new mechanistic insights relevant to seedling-based seagrass restoration under climate change.
Abstract
Successful establishment is a critical determinant of seagrass restoration, yet the molecular mechanisms underlying seedling acclimatisation to natural environments remain poorly understood. Here, we combined seasonal physiological observations, transcriptome profiling, and gene co-expression network analysis to investigate the mechanisms underlying the early post-transplantation phase of Posidonia oceanica, a dominant foundation seagrass species, following transplantation. Transplanted seedlings were compared with plants from adjacent natural meadows over the first six months after transplantation using leaf and root samples collected in spring, summer, and autumn. Tissue identity was the primary driver of transcriptomic variation, but transplanted seedlings remained transcriptionally distinct from plants in natural meadows throughout the study, with roots showing greater divergence than leaves, suggesting tissue-specific trajectories of post-transplantation acclimatisation. The early post-transplantation phase was characterised by the activation of genes associated with RNA processing, transcriptional regulation, and abscisic acid signalling. During a summer marine heatwave (28 °C), both plant groups induced conserved heat-response pathways, including heat-shock proteins and protein-folding mechanisms. Furthermore, transplanted seedlings maintained higher expression of genes involved in photosystem II repair and photoprotection and exhibited reduced leaf growth and extensive leaf necrosis, consistent with a greater requirement for photosynthetic maintenace under prolonged thermal stress. Gene co-expression network analysis revealed that regulatory networks governing structural integrity, hormone signalling, and defence were more stable in natural meadow plants, while transplanted seedlings progressively reorganized their gene co-expression patterns to resemble those of natural meadow plants, particularly in leaves. Our findings reveal tissue-specific molecular trajectories of acclimatisation during early seedling establishment and identify candidate molecular indicators of field acclimatisation and thermal stress responses, providing new mechanistic insights relevant to seedling-based seagrass restoration under climate change.
Genome-wide DNA-methylation revealed a progressive increase in the CHH context from Spring to Summer and Autumn, suggesting epigenetic reprogramming is happening over season and growing cycle, providing a genomic foundation for understanding how epigenetic memory contributes to phenology, developmental programming and long-term adaptation in long-lived plants.
Rosa Sanchez-Lucas, Joe He, Marcella Chirico et al.· Journal of Experimental Bota...· 0 citations
Abstract Effective ex situ propagation is critical for the conservation and restoration of threatened terrestrial orchids. However, large-scale propagation remains constrained by developmental bottlenecks including the transition from protocorms to plantlets with storage organs. Although cold exposure is often recommended to improve propagation success, the thermal conditions governing survival and post-dormancy performance remain poorly understood. We experimentally exposed protocorms of the Mediterranean terrestrial orchids Anacamptis coriophora, A. laxiflora, Himantoglossum hircinum, and H. robertianum to eight thermal treatments for 8 weeks, including controlled laboratory conditions and outdoor sites along an altitudinal gradient. Survival, shoot growth, and tuber development were quantified before and after summer dormancy, and their relationship with temperature descriptors was analysed using a model selection approach. Plant performance was consistently better explained by cumulative chilling exposure than by mean temperature alone, with different developmental processes responding to distinct thermal thresholds. Exposure to moderately low temperatures (10°C–12°C) determined survival and reserve accumulation before dormancy, while chilling below 6°C–7°C doubled post-dormancy shoot length in responsive species, revealing carry-over effects across growing seasons. Species differed markedly in their thermal responses; increased chilling reduced post-dormancy survival by ∼50% in A. coriophora but increased it two-fold in A. laxiflora, whereas H. robertianum developed leaves only following cold exposure. Winter chilling therefore appears to be a key regulator of seedling development in Mediterranean terrestrial orchids. The identified thermal thresholds provide a basis for improving ex situ propagation and restoration protocols, while highlighting species-specific vulnerabilities and responses to future climate change.
G. Deconninck, A. Gerakis, Victoria Chatzopoulou et al.· AoB Plants· 0 citations
Conifers are essential components of forest ecosystems; however, their reproductive development remains largely understudied due to their genomes' complexity. Here, we present a time-resolved spatial transcriptomics (ST) atlas of 88 tissue sections across three time points from developing reproductive and vegetative shoots in wild-type Norway spruce (Picea abies), as well as transition shoots from the acrocona mutant. By studying their different spatiotemporal gene expression dynamics, we identified molecular processes active during the vegetative-to-reproductive shift and their specific spatial domains in the shoots. We also identified and experimentally characterized the MADS-box gene DAL55, which is active during lateral organ development. Moreover, we shed light on the evolutionary relationships between gymnosperm and angiosperm YABBY genes, responsible for inner or outer cell layers in complex structures. Overall, our spatiotemporal atlas identifies genes, pathways, and evolutionary relationships associated with plant reproductive organs, providing a valuable resource for studying conifer reproductive development.
Sami Saarenpää, N. Zivi, Yuvarani Masarapu et al.· Cell· 0 citations
Climate change is increasing drought and heat stress in European forests, raising concerns about the capacity of long-lived tree species to respond to rapidly changing environmental conditions. While local adaptation has been documented in many forest trees, it remains unclear whether newly established seedlings, which form the forests of the future, are able to persist and adapt to these new climatic conditions. Here, we investigated genomic differences between naturally regenerated seedlings and trees of European beech (Fagus sylvatica) across the three regions of the German Biodiversity Exploratories using low-coverage whole-genome sequencing (∼5x) of 1,032 individuals. Population structure was primarily driven by geographic region, whereas genetic diversity was similar across life stages. Despite this genome-wide similarity, we detected allele frequency shifts between trees and seedlings, concentrated in narrow genomic windows. These shifts were strongest in surviving seedlings, suggesting that environmental filtering during early establishment may contribute to shaping the genetic composition of regenerating populations. The strongest signals were observed within the Swabian Alb, where sampled seedlings were 2-years old and had experienced a longer period of potential filtering prior to sampling. Genotype–environment association analyses identified loci associated with climatic variables, and subsequent GO enrichment analyses of genes linked to these loci revealed significantly more enriched GO terms in seedlings than in trees, suggesting stronger environmental filtering by the current climate in seedlings. In particular, we found associations with maximum air temperature, relative humidity, soil moisture, and precipitation, affecting genes involved in stress responses, growth, metabolism, and developmental processes. Together, our results demonstrate that young cohorts of European beech differ genetically from trees and reveal genomic patterns consistent with life-stage-dependent environmental filtering. These findings suggest that the genetic composition of early life-stages is already altered by current environmental conditions, possibly contributing to adaptation to new climatic conditions.
Marieke Lenga, L. Opgenoorth, K. Heer et al.· bioRxiv· 0 citations
Mountain ecosystems are disproportionately exposed to global warming, which may put alpine plant species in particular at risk. Plant species' migration and persistence depend on successful seed regeneration, with demographic traits such as germination being strongly sensitive to both present and ancestral climate. Germination may, thus, present a major bottleneck to alpine plant species under climate change, or they may cope through phenotypic plasticity. However, little is known about alpine plant germination under warming, its plasticity, and whether any of these are co‐determined by the climatic origin of the seeds. We investigated intraspecific variation in germination proportion and timing of six co‐occurring alpine plant species from different micro‐ and mesoclimatic origins as response to three temperature treatments using growth chambers. Elevation as well as topographic strata were used as proxies for mesoclimate and mean soil temperature, growing‐ as well as freezing‐degree‐days for microclimate. Our results show that species were plastic in germination proportion and timing in response to temperature, with all species germinating in the warmest treatment. Micro‐ and mesoclimatic origin affected germination traits but did not co‐determine species responses to the temperature treatments. We also demonstrated maternal climatic effects, with seeds from warmer microclimates displaying higher phenotypic plasticity. Furthermore, seeds originating from colder mesoclimates, i.e. the upper elevation range, generally germinated less. Our results suggest that global warming will impact alpine plant regeneration from seeds through concurrent effects during germination, climatic origin as well as shifts in germination timing. Importantly, our results indicate that regeneration from seed may contribute to defining the upper elevational limit of alpine plant species through climatic origin and maternal microclimatic effects.
Posidonia oceanica is a key foundation species of Mediterranean coastal ecosystems and is increasingly exposed to environmental stressors and local anthropogenic pressures. Understanding its early physiological responses is therefore essential for effective ecosystem monitoring and conservation. In this study, we investigated spatial variability in gene expression in P. oceanica across contrasting habitats within the eastern Aegean Sea. Samples were collected from outer bay, transition, and inner/coastal stations, and the expression of genes related to photosynthesis, antioxidant defense, heat stress and metal detoxification was quantified using RT-qPCR. Gene expression patterns revealed pronounced spatial heterogeneity across the bay. Photosynthesis-related genes were generally downregulated at several transition and inner/coastal stations, suggesting reduced photosynthetic performance under environmental stress. In contrast, antioxidant defense- and heat stress-related genes showed localized upregulation, indicating activation of protective mechanisms. Principal component analysis explained 55.54% of the total variance within the first two components and clearly separated stations according to their transcriptional profiles. These findings demonstrate that environmental heterogeneity within Gökova Bay is reflected at the molecular level in P. oceanica, generating site-specific transcriptional responses. The study highlights the potential of multigene expression approaches as sensitive early warning indicators for detecting sublethal stress in seagrass ecosystems and supporting biodiversity conservation and coastal management.
Esra Öztürk· Diversity· 0 citations
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