Transcriptome analysis of potential simple sequence repeat markers in Ammopiptanthus mongolicus

Ammopiptanthus mongolicus, an evergreen broadleaf legume shrub, can survive under conditions of high and low temperature, extreme salinity, and drought. This attribute makes it an ideal model for studying mechanisms of stress tolerance in plants. However, simple sequence repeat (SSR) resources for this species are insufficient in public databases. In this study, a total of 44,959 unigenes identified from the A. mongolicus transcriptome were used for SSR analysis by MIcroSAtellite (MISA). A total of 13,859 SSRs were found to be distributed within 10,409 unigenes, with an average length of 15 bp and an average density of one SSR per 4.4 kb. There were 222 different motif types in the A. mongolicus transcriptome, and mononucleotide repeats represented the main type, accounting for 44.2% of all SSRs. The (A/T)n repeat was the most frequent motif, accounting for 42.37% of all SSRs. We also performed Gene Ontology functional analysis, Kyoto Encyclopedia of Genes and Genomes database pathway analysis, and eggNOG analysis, and identified 6157, 2301, and 9845 unigenes containing SSRs in these three databases, respectively. The functional categorization of A. mongolicus unigenes containing SSRs revealed that these unigenes represent many transcribed genes with different functions. These data provide sequence information that may be used to improve molecular-assisted markers for the study A. mongolicus genetic diversity.