Nothofagus is the main component of southern South American temperate forests. Overexploitation in the past has led to the loss of 40% of the original distribution range. Genetic diversity as well as biological processes shaping the distribution of the genetic variation (e.g. gene flow) constitutes basic knowledge for the implementation of conservation measures and for the definition of Evolutionary Significant Units. Nuclear microsatellites are the marker of choice for gene flow and fine-scale genetic structure studies. We enlarged a previous set of microsatellites (SSRs) for South American Nothofagus species, with special concern to Nothofagus nervosa (Phil.) Dim. et Mil. Five new SSRs are presented with allele numbers up to 12 in a single population. The primers transferred well to five related species (N. obliqua (Mirb.) Oerst, N. glauca (Phil.) Krasser, N. dombeyi (Mirb.) Oerst , N. pumilio (Poepp et Endl.) Krasser and N. antarctica (G. Forster) Oerst, with allele numbers up to 11. The high level of polymorphism promises a sufficient power for gene flow and parentage analyses.

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Global warming is predicted to exert negative impacts on plant growth due to the damaging effect of high temperatures on plant physiology. Revealing the genetic architecture underlying the heat stress response is therefore crucial for the development of conservation strategies, and for breeding heat-resistant plant genotypes. Here we investigated the transcriptional changes induced by heat in Nothofagus pumilio, an emblematic tree species of the sub-Antarctic forests of South America. Through the performance of RNA-seq of leaves of plants exposed to 20°C (control) or 34°C (heat shock), we generated the first transcriptomic resource for the species. We also studied the changes in protein-coding transcripts expression in response to heat. We found 5,214 contigs differentially expressed between temperatures. The heat treatment resulted in a down-regulation of genes related to photosynthesis and carbon metabolism, whereas secondary metabolism, protein re-folding and response to stress were up-regulated. Moreover, several transcription factor families like WRKY or ERF were promoted by heat, alongside spliceosome machinery and hormone signaling pathways. Through a comparative analysis of gene regulation in response to heat in Arabidopsis thaliana, Populus tomentosa and N. pumilio we provide evidence of the existence of shared molecular features of heat stress responses across angiosperms, and identify genes of potential biotechnological application.

Key message Nothofagus alpina (Poepp. et Endl.) Oerst. and Nothofagus obliqua (Mirb.) Oerst forests have strong fine-scale spatial genetic structures. The intensity of genetic structure patterns differed according to species, stand development stages, life stages, and spatial arrangement of regeneration groups. This data becomes useful for forest management as it provides an understanding of how populations evolve as well as of the consequences of disturbances and enables the establishment of sampling strategies. Context The understanding of fine-scale spatial genetic structure in natural populations is useful for forest management. Although Nothofagus alpina (Poepp. et Endl.) Oerst. and N. obliqua (Mirb.) are important species of the Patagonian forest, little is known about the genetic structure of their populations. Aims The main objectives were to investigate the differences in fine-scale spatial genetic structure among mature tree populations of both species considering two stands at different development stages. Genetic structure was also evaluated among life stages and spatial distribution groups of regeneration within the old-growth stand. Methods Genetic structure was examined by microsatellite DNA analysis of regeneration and mature tree populations of both species (around 1300 individuals). Gene dispersal distance was additionally estimated. Results In both stands and species, strong fine-scale spatial genetic structure and short dispersal distance were found. This pattern was stronger in the early successional forest, in N. obliqua populations, in earlier life stages, and in scattered regeneration. Conclusion Stand development stages and recruitment patterns influence the fine-scale spatial genetic structure of both Nothofagus species. However, the genetic structure also differs between species.

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