title: RNA sequencing of Populus x canadensis roots identifies key molecular mechanisms underlying physiological adaption to excess zinc.
abstract: Populus x canadensis clone I-214 exhibits a general indicator phenotype in response to excess Zn, and a higher metal uptake in roots than in shoots with a reduced translocation to aerial parts under hydroponic conditions. This physiological adaptation seems mainly regulated by roots, although the molecular mechanisms that underlie these processes are still poorly understood. Here, differential expression analysis using RNA-sequencing technology was used to identify the molecular mechanisms involved in the response to excess Zn in root. In order to maximize specificity of detection of differentially expressed (DE) genes, we consider the intersection of genes identified by three distinct statistical approaches (61 up- and 19 down-regulated) and validate them by RT-qPCR, yielding an agreement of 93% between the two experimental techniques. Gene Ontology (GO) terms related to oxidation-reduction processes, transport and cellular iron ion homeostasis were enriched among DE genes, highlighting the importance of metal homeostasis in adaptation to excess Zn by P. x canadensis clone I-214. We identified the up-regulation of two Populus metal transporters (ZIP2 and NRAMP1) probably involved in metal uptake, and the down-regulation of a NAS4 gene involved in metal translocation. We identified also four Fe-homeostasis transcription factors (two bHLH38 genes, FIT and BTS) that were differentially expressed, probably for reducing Zn-induced Fe-deficiency. In particular, we suggest that the down-regulation of FIT transcription factor could be a mechanism to cope with Zn-induced Fe-deficiency in Populus. These results provide insight into the molecular mechanisms involved in adaption to excess Zn in Populus spp., but could also constitute a starting point for the identification and characterization of molecular markers or biotechnological targets for possible improvement of phytoremediation performances of poplar trees.
authors: BioLabs-Institute of Life Sciences, Scuola Superiore Sant'Anna, I-56127 Pisa, Italy.
authors: Andrea
authors: A
authors: Ariani
authors: BioLabs-Institute of Life Sciences, Scuola Superiore Sant'Anna, I-56127 Pisa, Italy.
authors: Daniela
authors: D
authors: Di Baccio
authors: BioLabs-Institute of Life Sciences, Scuola Superiore Sant'Anna, I-56127 Pisa, Italy.
authors: Stefania
authors: S
authors: Romeo
authors: Department of Biology, Università degli Studi di Pisa, I-56126 Pisa, Italy.
authors: Lara
authors: L
authors: Lombardi
authors: Department of Biology, Università degli Studi di Pisa, I-56126 Pisa, Italy.
authors: Andrea
authors: A
authors: Andreucci
authors: Department of Plant Physiology, Faculty of Natural Science, Comenius University in Bratislava, Bratislava, Slovakia; Institute of Chemistry, Slovak Academy of Sciences, Bratislava, Slovakia.
authors: Alexander
authors: A
authors: Lux
authors: Department of Biosciences, Università degli Studi di Milano, Milano, Italy.
authors: David Stephen
authors: DS
authors: Horner
authors: BioLabs-Institute of Life Sciences, Scuola Superiore Sant'Anna, I-56127 Pisa, Italy.
authors: Luca
authors: L
authors: Sebastiani
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D063990:Gene Ontology; D017343:Genes, Plant / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D032107:Populus / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D017423:Sequence Analysis, RNA; D059467:Transcriptome / Q000187:drug effects; D015032:Zinc / Q000494:pharmacology*
chemical_list: D015032:Zinc