Center for Forest Research and Institute for Systems and Integrative Biology, 1030 rue de la Médecine, Université Laval, Québec QC G1V 0A6, Canada.
Canada Research Chair in Forest Genomics, 1030 rue de la Médecine, Université Laval, Québec QC G1V 0A6, Canada.
Tree Physiol. 2018 Mar 1;38(3):442-456. doi: 10.1093/treephys/tpx125.
Temperatures are expected to increase over the next century in all terrestrial biomes and particularly in boreal forests, where drought-induced mortality has been predicted to rise. Genomics research is helping to develop hypotheses regarding the molecular basis of drought tolerance and recent work proposed that the osmo-protecting dehydrin proteins have undergone a clade-specific expansion in the Pinaceae, a major group of conifer trees. The objectives of this study were to identify all of the putative members of the gene family, trace their evolutionary origin, examine their structural diversity and test for drought-responsive expression. We identified 41 complete dehydrin coding sequences in Picea glauca, which is four times more than most angiosperms studied to date, and more than in pines. Phylogenetic reconstructions indicated that the family has undergone an expansion in conifers, with parallel evolution implicating the sporadic resurgence of certain amino acid sequence motifs, and a major duplication giving rise to a clade specific to the Pinaceae. A variety of plant dehydrin structures were identified with variable numbers of the A-, E-, S- and K-segments and an N-terminal (N1) amino acid motif including assemblages specific to conifers. The expression of several of the spruce dehydrins was tissue preferential under non-stressful conditions or responded to water stress after 7-18 days without watering, reflecting changes in osmotic potential. We found that dehydrins with N1 K2 and N1 AESK2 sequences were the most responsive to the lack of water. Together, the family expansion, drought-responsive expression and structural diversification involving loss and gain of amino acid motifs suggests that subfunctionalization has driven the diversification seen among dehydrin gene duplicates. Our findings clearly indicate that dehydrins represent a large family of candidate genes for drought tolerance in spruces and in other Pinaceae that may underpin adaptability in spatially and temporally variable environments.
预计在未来一个世纪内，所有陆地生物群系的温度都会升高，特别是在预测干旱导致死亡率上升的北方森林。基因组学研究有助于提出关于耐旱性分子基础的假设，最近的工作提出，亲水性脱水蛋白在松科中发生了特定分支的扩张，松科是针叶树的一个主要类群。本研究的目的是鉴定基因家族的所有假定成员，追溯其进化起源，研究其结构多样性，并检测其对干旱的响应表达。我们在白云杉中鉴定了 41 个完整的脱水素编码序列，这是迄今为止研究的大多数被子植物的四倍，也是松树的两倍多。系统发育重建表明，该家族在针叶树中发生了扩张，平行进化暗示某些氨基酸序列基序的零星复兴，而主要的复制产生了一个特定于松科的分支。鉴定出多种植物脱水素结构，其 A-、E-、S-和 K-段以及 N 端（N1）氨基酸基序的数量可变，包括特定于针叶树的集合。在非胁迫条件下，几种云杉脱水素的表达具有组织偏好性，或者在 7-18 天不浇水后对水分胁迫产生反应，反映了渗透势的变化。我们发现，具有 N1K2 和 N1AESK2 序列的脱水素对缺水最敏感。总的来说，家族扩张、对干旱的响应表达以及结构多样化，包括氨基酸基序的丢失和获得，表明亚功能化推动了脱水素基因重复之间的多样化。我们的研究结果清楚地表明，脱水素代表了云杉和其他松科植物中耐旱性的候选基因大家族，可能为在空间和时间上变化的环境中提供适应性提供支持。
