Bradshaw H D
Department of Biology, University of Washington, Seattle, WA 98195, USA.
New Phytol. 2005 Jul;167(1):81-8. doi: 10.1111/j.1469-8137.2005.01408.x.
Plant tolerance of serpentine soils is potentially an excellent model for studying the genetics of adaptive variation in natural populations. A large-scale viability screen of Arabidopsis thaliana mutants on a defined nutrient solution with a low Ca(2+) : Mg(2+) ratio (1 : 24 mol : mol), typical of serpentine soils, yielded survivors with null alleles of the tonoplast calcium-proton antiporter CAX1. cax1 mutants have most of the phenotypes associated with tolerance to serpentine soils, including survival in solutions with a low Ca(2+) : Mg(2+) ratio; requirement for a high concentration of Mg(2+) for maximum growth; reduced leaf tissue concentration of Mg(2+); and poor growth performance on 'normal' levels of Ca(2+) and Mg(2+). A physiological model is proposed to explain how loss-of-function cax1 mutations could produce all these phenotypes characteristic of plants adapted to serpentine soils, why 'normal' plants are unable to survive on serpentine soil, and why serpentine-adapted plants are unable to compete on 'normal' soils.
植物对蛇纹岩土的耐受性可能是研究自然种群适应性变异遗传学的一个绝佳模型。在具有典型蛇纹岩土低钙（2+）：镁（2+）比例（1：24摩尔：摩尔）的特定营养液中对拟南芥突变体进行大规模活力筛选，得到了液泡膜钙-质子反向转运蛋白CAX1无效等位基因的存活植株。cax1突变体具有大多数与蛇纹岩土耐受性相关的表型，包括在低钙（2+）：镁（2+）比例溶液中的存活能力；最大生长所需的高浓度镁（2+）；叶片组织中镁（2+）浓度降低；以及在“正常”钙（2+）和镁（2+）水平下生长表现不佳。提出了一个生理模型来解释功能丧失的cax1突变如何产生所有这些适应蛇纹岩土的植物特征表型，为什么“正常”植物不能在蛇纹岩土上存活，以及为什么适应蛇纹岩土的植物不能在“正常”土壤上竞争。
