Effects of arbuscular mycorrhizal symbiosis on growth, nutrient and metal uptake by maize seedlings (Zea mays L.) grown in soils spiked with Lanthanum and Cadmium.

Multiple contaminants can affect plant-microbial remediation processes because of their interactive effects on environmental behaviour, bioavailability and plant growth. Recent studies have suggested that arbuscular mycorrhizal fungi (AMF) can facilitate the revegetation of soils co-contaminated with rare earth elements (REEs) and heavy metals. However, little is known regarding the role of AMF in the interaction of REEs and heavy metals. A pot experiment was conducted to evaluate the effects of Claroideoglomus etunicatum on the biomass, nutrient uptake, metal uptake and translocation of maize grown in soils spiked with Lanthanum (La) and Cadmium (Cd). The results indicated that individual and combined applications of La (100 mg kg-1) and Cd (5 mg kg-1) significantly decreased root colonization rates by 22.0%-35.0%. With AMF inoculation, dual-metal treatment significantly increased maize biomass by 26.2% compared to single-metal treatment. Dual-metal treatment significantly increased N, P and K uptake by 20.1%-76.8% compared to single-metal treatment. Dual-metal treatment significantly decreased shoot La concentration by 52.9% compared to single La treatment, whereas AM symbiosis caused a greater decrease of 87.8%. Dual-metal treatment significantly increased shoot and root Cd concentrations by 65.5% and 58.7% compared to single Cd treatment and the La translocation rate by 142.0% compared to single La treatment, whereas no difference was observed between their corresponding treatments with AMF inoculation. Furthermore, AMF had differential effects on the interaction of La and Cd on metal uptake and translocation under the background concentrations of soil metals. Taken together, these results indicated that AMF significantly affected the interaction between La and Cd, depending on metal types and concentrations in soils. These findings promote a further understanding of the contributions of AMF to the phytoremediation of co-contaminated soil.

Development and characterization of EST-SSR markers in Stipa breviflora (Poaceae).

PREMISE OF THE STUDY: Stipa breviflora (Poaceae) is one of the dominant species of the desert steppe in the eastern Eurasian grasslands. Simple sequence repeat (SSR) markers were developed for use in genetic diversity studies of this species. METHODS AND RESULTS: A total of 1954 potentially polymorphic loci were obtained by comparing transcriptome data of eight different S. breviflora individuals. We selected 81 loci to verify polymorphism and 63 loci amplified, of which 21 loci exhibited polymorphism. The number of alleles per locus varied from two to 24, the observed heterozygosity ranged from 0.083 to 0.958, and the expected heterozygosity ranged from 0.396 to 0.738. CONCLUSIONS: These newly identified SSR loci can be used for population genetic and landscape genetic studies of S. breviflora. In addition, 14 loci also amplified in six related Stipa species (S. grandis, S. krylovii, S. bungeana, S. aliena, S. gobica, and S. purpurea).

Identification of Salt-Stress-Induced Genes from the RNA-Seq Data of Reaumuria trigyna Using Differential-Display Reverse Transcription PCR.

Next generation sequencing (NGS) technologies have been used to generate huge amounts of sequencing data from many organisms. However, the correct choice of candidate genes and prevention of false-positive results computed from digital gene expression (DGE) of RNA-seq data are vital when using these genetic resources. We indirectly identified 18 salt-stress-induced Reaumuria trigyna transcripts from the transcriptome sequencing data using differential-display reverse transcription PCR (DDRT-PCR) combined with local BLAST searches. Highly consistent with the DGE results, the quantitative real-time PCR expression patterns of these transcripts showed strong upregulation by salt stress, suggesting that these genes may play important roles in R. trigyna's survival under high-salt environments. The method presented here successfully identified responsive genes from the massive amount of RNA-seq data. Thus, we suggest that DDRT-PCR could be employed to mine NGS data in a wide range of applications in transcriptomic studies. In addition, the genes identified in the present study are promising candidates for further elucidation of the salt tolerance mechanisms in R. trigyna.

Transcriptomic profiling of the salt-stress response in the wild recretohalophyte Reaumuria trigyna.

BACKGROUND: Reaumuria trigyna is an endangered small shrub endemic to desert regions in Inner Mongolia. This dicotyledonous recretohalophyte has unique morphological characteristics that allow it to tolerate the stress imposed by semi-desert saline soil. However, it is impossible to explore the mechanisms underlying this tolerance without detailed genomic information. Fortunately, newly developed high-throughput sequencing technologies are powerful tools for de novo sequencing to gain such information for this species. RESULTS: Two sequencing libraries prepared from control (C21) and NaCl-treated samples (T43) were sequenced using short reads sequencing technology (Illumina) to investigate changes in the R. trigyna transcriptome in response to salt stress. Among 65340 unigenes, 35495 (52.27%) were annotated with gene descriptions, conserved domains, gene ontology terms, and metabolic pathways with a cut-off E-value of 10-5. These included 44 Gene Ontology (GO) terms, 119 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and 25 Clusters of Orthologous Groups families. By comparing the transcriptomes from control and NaCl-treated plants, 5032 genes showed significantly differences in transcript abundance under salt stress (false discovery rate ≤ 0.001 and |log2Ratio| ≥ 1). These genes were significantly enriched in 29 KEGG pathways and 26 GO terms. The transcription profiles indicated that genes related to ion transport and the reactive oxygen species scavenging system were relevant to the morphological and physiological characteristics of this species. The expression patterns of 30 randomly selected genes resulted from quantitative real-time PCR were basically consistent with their transcript abundance changes identified by RNA-seq. CONCLUSIONS: The present study identified potential genes involved in salt tolerance of R. trigyna. The globally sequenced genes covered a considerable proportion of the R. trigyna transcriptome. These data represent a genetic resource for the discovery of genes related to salt tolerance in this species, and may be a useful source of reference sequences for closely related taxa. These results can also further our understanding of salt tolerance in other halophytes surviving under sodic stress.