Neo-functionalization Among Tandem Duplicated Stress-Relevant Genes in Thellungiella species

Thellungiella is a crucifer genus closely related to Arabidopsis, characterized by extreme tolerance to abiotic stresses. Recent genome assemblies and annotations of two Thellungiella species, T. parvula and T. salsuginea, enable comparative studies revealing the genomic basis of adaptation to habitats stressful to most plants, including Arabidopsis.  Irrespective of different chromosome numbers and genome sizes, A. thaliana and the two Thellungiella species share extensive co-linearity over their genomes with the size of gene spaces largely conserved.  Glaring differences were observed in copy numbers of stress-related genes. In all species, more than 10% of the genes were found in tandem gene arrays. However, only half of the tandem duplication events are shared between the Thellungiella species and A. thaliana.  Neo-functionalization of duplicated genes resulted in novel expression patterns as well as gene functions among stress-related genes.  For example, tandem duplication of HKT1 was observed only in Thellungiella species. One of the duplicated copies evolved into a Thellungiella-specific allele with a novel protein function.  Putative neo-functionalization of duplicated genes in timing and expression strength across the genomes will be also discussed.