Goessen Roos, Isabel Nathalie, Wehenkel Christian, Gonzales-Vigil Eliana, Hui Osmond, Touchette Lyne, Gagné Justine, Lamara Mebarek, Bousquet Jean, Mock Karen E, Soolanayakanahally Raju, Porth Ilga
Institute for Systems and Integrative Biology (IBIS), Pavillon Charles-Eugène-Marchand, 1030 avenue de la Médecine, Université Laval, Québec, QC G1V 0A6, Canada.
Département des Sciences du Bois et de la Forêt, Faculté de Foresterie, de Géographie et de Géomatique, Pavillon Abitibi-Price, 2405 rue de la Terrasse, Université Laval, Québec, QC G1V 0A6, Canada.
Tree Physiol. 2025 Aug 5;45(8). doi: 10.1093/treephys/tpaf087.
Local adaptation can lead to the intraspecific variation in a species' genetic makeup, shaping both its physiological and morphological traits as well as its molecular responses. In this study, we assessed variation in key functional leaf traits, such as stomata density, carbon and nitrogen content, cuticular wax composition and leaf shapes, within the transcontinental North American Populus tremuloides Michaux (quaking aspen) by sampling individuals from its four major genetic lineages. We also performed a small-scale common garden experiment with imposed higher temperature and drought stress during which we sampled for transcriptomes using RNAseq and performed physiological measurements to obtain insights into the intraspecific responses among aspen lineages to such abiotic stressors. Our findings revealed several differences in functional traits indicative of local adaptation, such as variation in cuticular wax content, petiole lengths and δ13C. Notably, stomatal density was significantly associated with mean annual precipitation. Moreover, genotypes from the most southern lineage (Mexico) exhibited the largest decline in net photosynthesis under drought, suggesting a more conservative water-use strategy. Gene expression analyses revealed numerous differentially expressed genes under different stress conditions and in different lineages, with overlaps with previous gene selection scans, confirming their possible roles in local adaptation. Weighted gene co-expression network analysis further identified 22 co-expressed gene modules, several of which strongly associated with temperature responses and geographic origin of genetic lineage. Our findings highlight substantial intraspecific variation in functional traits and gene expression patterns in P. tremuloides linked to geographical origin and local environmental conditions. Understanding such adaptive variation is crucial for predicting how forest trees may cope with and adapt to the challenges of climate change.
局部适应可导致一个物种基因组成的种内变异，塑造其生理和形态特征以及分子反应。在本研究中，我们通过从北美颤杨（Populus tremuloides Michaux）的四个主要遗传谱系中取样个体，评估了其跨大陆分布范围内关键功能叶性状的变异，如气孔密度、碳和氮含量、表皮蜡质成分和叶形。我们还进行了一个小规模的共同花园实验，施加更高的温度和干旱胁迫，在此期间我们使用RNAseq对转录组进行取样，并进行生理测量，以深入了解白杨谱系对这种非生物胁迫源的种内反应。我们的研究结果揭示了功能性状方面的几个差异，这些差异表明存在局部适应，如表皮蜡质含量、叶柄长度和δ13C的变异。值得注意的是，气孔密度与年平均降水量显著相关。此外，最南部谱系（墨西哥）的基因型在干旱条件下净光合作用下降幅度最大，表明其水分利用策略更为保守。基因表达分析揭示了在不同胁迫条件和不同谱系下有大量差异表达基因，与之前的基因选择扫描结果有重叠，证实了它们在局部适应中的可能作用。加权基因共表达网络分析进一步确定了22个共表达基因模块，其中几个与温度反应和遗传谱系的地理起源密切相关。我们的研究结果突出了北美颤杨在功能性状和基因表达模式方面与地理起源和当地环境条件相关的大量种内变异。了解这种适应性变异对于预测森林树木如何应对和适应气候变化的挑战至关重要。
