title: On the salty side of life: molecular, physiological and anatomical adaptation and acclimation of trees to extreme habitats.
abstract: Saline and sodic soils that cannot be used for agriculture occur worldwide. Cultivating stress-tolerant trees to obtain biomass from salinized areas has been suggested. Various tree species of economic importance for fruit, fibre and timber production exhibit high salinity tolerance. Little is known about the mechanisms enabling tree crops to cope with high salinity for extended periods. Here, the molecular, physiological and anatomical adjustments underlying salt tolerance in glycophytic and halophytic model tree species, such as Populus euphratica in terrestrial habitats, and mangrove species along coastlines are reviewed. Key mechanisms that have been identified as mediating salt tolerance are discussed at scales from the genetic to the morphological level, including leaf succulence and structural adjustments of wood anatomy. The genetic and transcriptomic bases for physiological salt acclimation are salt sensing and signalling networks that activate target genes; the target genes keep reactive oxygen species under control, maintain the ion balance and restore water status. Evolutionary adaptation includes gene duplication in these pathways. Strategies for and limitations to tree improvement, particularly transgenic approaches for increasing salt tolerance by transforming trees with single and multiple candidate genes, are discussed.
authors.affiliation: Forstbotanik und Baumphysiologie, Büsgen-Institut, Georg-August Universität Göttingen, Göttingen, 37077, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Polle
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, China.
authors.forename: Shaoliang
authors.initials: S
authors.lastname: Chen
mesh_terms: D000064:Acclimatization; D000222:Adaptation, Physiological; D017753:Ecosystem; D018506:Gene Expression Regulation, Plant; D005818:Genetic Engineering; D006706:Homeostasis; D000069600:Plant Breeding / Q000379:methods; D018515:Plant Leaves / Q000502:physiology; D032107:Populus / Q000502:physiology; D055049:Salt Tolerance; D012965:Sodium Chloride / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D014197:Trees / Q000033:anatomy & histology* / Q000235:genetics / Q000502:physiology*; D053833:Wetlands
chemical_list: D012987:Soil; D012965:Sodium Chloride
keywords: Populus; adaptive trait; antioxidative systems; leaf succulence; mangrove; salt signalling network; sodium; transcriptome; transformation; wood