Project description:Gene copy number variation (CNV) is a form of genetic polymorphism that contributes significantly to genome size and function but remains poorly characterized due to technological limitations. Inter-specific comparisons of CNVs in recently diverged plant species are crucial to uncover selection patterns underlying adaptation of a species to stressful environments. Especially given that gene amplifications have long been implicated in emergence of species-specific traits, we conducted a genome-wide survey to identify species-specific gene copy number expansions and deletions in the model extremophile species - Arabidopsis halleri that has diverged in evolutionarily recent time from Arabidopsis thaliana. Cross-species cDNA array based comparative genomic hybridization was employed to compare and identify gene copy number variation in the two sister-species - the metallophyte Arabidopsis halleri and non-metallophyte Arabidopsis lyrata, both relative to Arabidopsis thaliana. We uncovered an unprecedented level of gene copy number polymorphism in Arabidopsis halleri, with a species-specific enrichment of metal homeostasis function in the genes found to be copy number expanded, thus indicating CNV as a mechanism that underlies the key physiological trait of metal hyperaccumulation and hypetolerance in A. halleri.
Project description:The model Zn hyperaccumulators Arabidopsis halleri and Noccaea caerulescens share elevated nicotianamine synthase (NAS) expression relative to non-accumulators among a core of alterations in metal homeostasis gene expression. Suppression of AhNAS2 expression by RNAi resulted in strongly reduced root NA accumulation and a concomitant decrease in root-to-shoot-translocation of Zn but not of other micronutrients. Few secondary effects on the root transcriptome were detected by microarray analysis.
