Hendrickson Brandon T, Stamps Caitlyn, Patterson Courtney M, Strickland Hunter, Foster Michael, Albano Lucas J, Kim Audrey Y, Kim Paul Y, Kooyers Nicholas J
Department of Biology, University of Louisiana, Lafayette, 410 E. St. Mary Blvd., Lafayette, LA 70503, USA.
School of Biological Science, Louisiana Technical University, 1 Adams Blvd., Ruston, LA 71272, USA.
Ann Bot. 2025 Aug 16;135(7):1377-1392. doi: 10.1093/aob/mcaf037.
Success during colonization is likely to depend on growing quickly and tolerating novel and stressful environmental conditions. However, rapid growth, stress avoidance and stress tolerance are generally considered divergent physiological strategies.
We evaluated how white clover (Trifolium repens) has evolved to a divergent water regime following introduction to North America. We conducted RNA sequencing within a dry-down experiment using accessions from low- and high-latitude populations from native and introduced ranges and assessed variation in dehydration avoidance (ability to avoid wilting) and dehydration tolerance (ability to survive wilting).
Introduced populations were better at avoiding dehydration, but poorer at tolerating dehydration than native populations. There was a strong negative correlation between avoidance and tolerance traits, and expression of most drought-associated genes exhibited similar trade-offs. Candidate genes with expression strongly associated with dehydration avoidance were linked to stress signalling, closing stomata and producing osmoprotectants. However, genes with expression linked to dehydration tolerance were associated with avoiding excessive production of reactive oxygen species and toxic bioproducts of stress responses. Several candidate genes showed differential expression patterns between native and introduced ranges and could underlie differences in drought resistance syndromes between ranges.
These results suggest that there has been strong selection following introduction for dehydration avoidance at the cost of surviving dehydration. More broadly, trade-offs between dehydration avoidance and tolerance responses are likely to exist at both the genetic and phenotypic scales that will influence evolutionary responses and potentially limit the global spectrum of plant form and function.
在定殖过程中的成功可能取决于快速生长以及耐受新的和有压力的环境条件。然而，快速生长、避逆和耐逆通常被认为是不同的生理策略。
我们评估了白三叶草（Trifolium repens）在引入北美后是如何进化以适应不同水分状况的。我们在一个干旱实验中，对来自原生和引入区域的低纬度和高纬度种群的材料进行了RNA测序，并评估了脱水避免（避免萎蔫的能力）和脱水耐受（从萎蔫中存活的能力）的变异。
引入种群在避免脱水方面表现更好，但在耐受脱水方面比原生种群差。避逆和耐受性状之间存在很强的负相关，并且大多数与干旱相关基因的表达也表现出类似的权衡。与脱水避免强烈相关的表达候选基因与胁迫信号传导、关闭气孔和产生渗透保护剂有关。然而，与脱水耐受相关的表达基因与避免活性氧的过度产生以及胁迫反应的有毒生物产物有关。几个候选基因在原生和引入区域之间表现出不同的表达模式，可能是不同区域抗旱综合征差异的基础。
这些结果表明，引入后存在以耐受脱水为代价的强烈选择以避免脱水。更广泛地说，脱水避免和耐受反应之间的权衡可能在遗传和表型尺度上都存在，这将影响进化反应，并可能限制植物形态和功能的全球范围。
