W184 Genomic Comparison of Arabidopsis and its Haplophytic Relative Thellungiella Salsuginea

Date: Sunday, January 15, 2012
Time: 8:40 AM
Room: Golden Ballroom
Xiangfeng Wang , University of Arizona, Tucson, AZ
Thellungiella salsuginea, a close relative of Arabidopsis thaliana, has been studied as an extremophile model plant, owing to its superior ability to grown in extreme environments. Here we report a high-quality genome sequence of T.salsuginea completed by BAC-to-BAC method. We surprisingly found half of the assembled T.salsuginea genome (243 Mb) is composed of long-span heterochromatins spreading bidirectionally from the centromeres, evidencing a long evolutionary history of fighting the massive activation of transposable elements induced by environmental cues. Comparison between T.salsuginea and Arabidopsis shows 82% of protein-coding genes are distributed in a syntenic manner, regardless of in the euchromatic or heterochromatic parts of the chromosomes. Gene function enrichment analysis indicates the halophytic characteristics of T.salsuginea may be attributed to a mixture of tandem duplication and segmental duplication events causing gene dosage changes in very specific functional categories: in contrast of slight copy-number variation of the gene families in the core SOS pathways established in Arabidopsis, major gene duplication events occur on the components of protein-ubiquitination pathways and a few select genes for signal transduction. Moreover, the number of cellular component genes is also noticeably increased to potentially strengthen the physical defense against stress. Accordingly, certain microRNAs in T.salsuginea targeting these genes are also duplicated. Our analysis provides a new insight in interpreting the evolution of halophytic plants that the posttranscriptional regulators are enhanced in copy-number dosage to fine-tune the cellular pathways and structural composition to tolerate environmental abiotic stress.