Association of microsatellite pairs with segmental duplications in insect genomes

Simple sequence repeats drive genome plasticity and promote adaptive evolution in penaeid shrimp

Simple sequence repeats (SSRs) are rare (approximately 1%) in most genomes and are generally considered to have no function. However, penaeid shrimp genomes have a high proportion of SSRs (>23%), raising the question of whether these SSRs play important functional and evolutionary roles in these SSR-rich species. Here, we show that SSRs drive genome plasticity and adaptive evolution in two penaeid shrimp species, Fenneropenaeus chinensis and Litopenaeus vannamei. Assembly and comparison of genomes of these two shrimp species at the chromosome-level revealed that transposable elements serve as carriers for SSR expansion, which is still occurring. The remarkable genome plasticity identified herein might have been shaped by significant SSR expansions. SSRs were also found to regulate gene expression by multi-omics analyses, and be responsible for driving adaptive evolution, such as the variable osmoregulatory capacities of these shrimp under low-salinity stress. These data provide strong evidence that SSRs are an important driver of the adaptive evolution in penaeid shrimp.

Genome-wide identification and analysis of the Populus trichocarpa TIFY gene family

The plant-specific TIFY proteins are widely present in land plants and play the important roles in the regulation of plant stress-responses. In this study, we carried out a bioinformatics analysis of TIFY genes in Populus trichocarpa by determining the phylogenetic relationship, chromosomal location and gene structure and expression profiles analysis under stresses. The 24 TIFY genes were identified and classified into four subfamilies (ZML, JAZ, PPD and TIFY). The 24 TIFY genes were irregularly located on 13 of the 19 chromosomes; ten gene pairs were involved in large-scale interchromosomal segmental duplication events; we identified 17 collinear TIFY gene pairs in the Populus trichocarpa genome. Numerous abiotic stress cis-elements were widely found in the promoter regions. Analysis of the Ka/Ks ratios indicated that the paralogs of the PtTIFY family principally underwent purifying selection. Microarray data and qRT-PCR analysis revealed that 24 PtTIFY genes were differentially expressed in various tissues. Quantitative real-time RT-PCR analysis of TIFY genes expression in response to salt, JA hormones and low-temperature stress revealed their stress-responses profiles. The results of this study provided valuable information for further exploration of the TIFY gene family in Populus trichocarpa.

APMicroDB: A microsatellite database of Acyrthosiphon pisum

Pea aphids represent a complex genetic system that could be used for QTL analysis, genetic diversity and population genetics studies. Here, we described the development of first microsatellite repeat database of the pea aphid (APMicroDB), accessible at “http://deepaklab.com/aphidmicrodb”. We identified 3,40,233 SSRs using MIcroSAtellite (MISA) tool that was distributed in 14,067 (out of 23,924) scaffold of the pea aphid. We observed 89.53% simple repeats of which 73.41% were mono-nucleotide, followed by di-nucleotide repeats. This database stored information about the repeats kind, GC content, motif type (mono - hexa), genomic location etc. We have also incorporated the primer information derived from Primer3 software of the 250bp flanking region of the identified marker. Blast tool is also provided for searching the user query sequence for identified marker and their primers. This work has an immense use for scientific community working in the field of agricultural pest management, QTL mapping, and host-pathogen interaction analysis.

Genome microsatellite diversity within the Apicomplexa phylum

The Apicomplexa phylum groups include unicellular and obligate intracellular protozoan parasites with an apical complex used for attachment and invasion to host cells. In this study, we analyze single sequence repeats (SSRs) in the whole genome of 20 apicomplexan organisms that represent four different lineages within the phylum. Only perfect SSRs with at least 12 nucleotides and composed of 2-6 mers were included. To better understand the association of SSR types with the genomic regions, the SSRs were classified accordingly with the genomic location into exon, intron and intergenic categories. Our results showed heterogeneous SSRs density within the studied genomes. However, the most frequent SSRs types were di- and tri-nucleotide repeats. The former was associated with intergenic regions, while the latter was associated with exon regions.