Genetic Diversity Of Thellungiella Salsuginea

Thellungiella salsuginea is an annual herbaceous dicotyledon which is a relative of Arabidopsis thaliana, both of which share many similarities. They both have a small genome (n=7), short life span (3-4 months), abundant seed production. Besides, T. salsuginea is able to complete its life cycle under condition of 100mM NaCl. Therefore, T. salsuginea is suitable to be model plant for research of salt-tolerance. Although there was research about salt-tolerance of T. salsuginea, few concerns has been shown on genetic diversity. In present research, we investigated the genetic diversity of the populations of T. salsuginea by means of SSR, chloroplast DNA (cpDNA), and nr ITS (Nuclear ribosomal Internal Transcriber Spacer) region.The genetic diversity of T. salsuginea within and among 18 natural populations across the entire range of the species has been investigated by SSR, of which 5 out of 15 pairs of primers showed polymorphism. The result showed that the variety of the effective number of alleles was small. The mean number of alleles is 1.249 (1.037-1.997). There was no heterozygote within the whole populations considering Ho=0. Mean value of FST was 0.671, which showed that there was high genetic differentiation among populations while mean value of Nm was 0.122. The result of structure suggests the existence of genetic differences between the two groups of populations. After being artificially divided into two groups corresponding to east and west geographical distributions, populations from East China (1-16) and populations from Xinjiang and Canada (17,18), the analysis of molecular variation (AMOVA) indicated that 81.89% of total variation was partitioned between the two groups, while only 8.71% was partitioned within populations.We also investigated genetic diversity of T. salsuginea inferred from 10 chloroplast loci and nr ITS region. Only 3 haplotypes were detected on the psbA-trnH region. No haplotype was detected on ITS region.We investigated nucleotide diversity of 12 single-copy nuclear loci and 9 genotypes were detected. Haplotype networks showed that haplotypes of Xinjiang and Canada were significantly different from the others. We also found that the nucleotide diversity of T. salsuginea is much lower than other species (πs= 0.00048). After calculating the nonsynonymous substitutions (dN) and synonymous substitutions (dS), we found theωvalue was small (ω<1) in all the genes that had been detected.Our results revealed the evolutionary history of T. salsuginea. Our finding suggested that the genetic structure of T. salsuginea was relatively simple as a consequence of long-distance dispersal (LDD). However, the genetic structure was complicated in the east of China. It is obvious that T. salsuginea collected from this region has been through a rapid expansion.