Jin Yuan Chen’s research while affiliated with Qinghai Normal University and other places

The species of Orinus (Poaceae) are important alpine plants with a variety of phenotypic traits and potential usages in molecular breeding toward drought-tolerant forage crops. However, the genetic basis of evolutionary adaption and diversification in the genus is still unclear. In the present study, we obtained transcriptomes for the two most divergent species, O. thoroldii and O. kokonoricus, using the Illumina platform and de novo assembly. In total, we generated 23,029 and 24,086 unigenes with N50 values of 1188 and 1203 for O. thoroldii and O. kokonoricus respectively, and identified 19,005 pairs of putative orthologs between the two species of Orinus. For these orthologs, estimations of non-synonymous/synonymous substitution rate ratios indicated that 568 pairs may be under strongly positive selection (Ka/Ks > 1), and Gene Ontogeny (GO) enrichment analysis revealed that significantly enriched pathways were in DNA repair and resistance to abiotic stress. Meanwhile, the divergence times of species between O. thoroldii and O. kokonoricus occurred 3.2 million years ago (Mya), and the recent evolutionary branch is an allotetraploid species, Cleistogenes songorica. We also detected a Ks peak of ∼0.60 for Orinus. Additionally, we identified 188 pairs of differentially expressed genes (DEGs) between the two species of Orinus, which were significantly enrich in stress resistance and lateral root development. Thus, we considered that the species diversification and evolutionary adaption of this genus was initiated by environmental selection, followed by phenotypic differentiation, finally leading to niche separation in the Qinghai-Tibet Plateau.

Psammochloa villosa is a desert plant growing in Northwest China with considerable resistance to abiotic stress, including drought, cold, and salt. To facilitate future studies of stress resistance in Psammochloa villosa, we sought to establish a suite of reference (or housekeeping) genes for utilization within future gene expression studies. Specifically, we selected nine candidate genes based on prior studies and new transcriptomic data for P. villosa, and we evaluated their expression stability in three different tissues of P. villosa under different treatments simulating abiotic stress conditions using four different bioinformatics assessments. Our results showed that TIP41 (TIP41-like family protein) was the most stable reference gene in drought- and salt-stressed leaves and salt-stressed stems, ELF-1α (elongation factor 1-α) was the most stable in cold-stressed leaves and drought- and salt-stressed roots, ACT (actin) was the most stable in drought-stressed stems, TUA (α-tubulin) was the most stable in cold-stressed stems, and 18S rRNA (18S ribosomal RNA) was the most stable in cold-stressed roots. Additionally, we tested the utility of these candidate reference genes to detect the expression pattern of P5CS (Δ¹-pyrroline-5-carboxylate synthetase), which is a drought-related gene. This study is the first report on selecting and validating reference genes of P. villosa under various stress conditions and will benefit future investigations of the genomic mechanisms of stress resistance in this ecologically important species.