Transcriptomics Reveals Host-Dependent Differences of Polysaccharides Biosynthesis in Cynomorium songaricum

Cynomorium songaricum is a root holoparasitic herb that is mainly hosted in the roots of Nitraria roborowskii and Nitraria sibirica distributed in the arid desert and saline-alkaline regions. The stem of C. songaricum is widely used as a traditional Chinese medicine and applied in anti-viral, anti-obesity and anti-diabetes, which largely rely on the bioactive components including: polysaccharides, flavonoids and triterpenes. Although the differences in growth characteristics of C. songaricum between N. roborowskii and N. sibirica have been reported, the difference of the two hosts on growth and polysaccharides biosynthesis in C. songaricum as well as regulation mechanism are not limited. Here, the physiological characteristics and transcriptome of C. songaricum host in N. roborowskii (CR) and N. sibirica (CS) were conducted. The results showed that the fresh weight, soluble sugar content and antioxidant capacity on a per stem basis exhibited a 3.3-, 3.0- and 2.1-fold increase in CR compared to CS. A total of 16,921 differentially expressed genes (DEGs) were observed in CR versus CS, with 2573 characterized genes, 1725 up-regulated and 848 down-regulated. Based on biological functions, 50 DEGs were associated with polysaccharides and starch metabolism as well as their transport. The expression levels of the selected 37 genes were validated by qRT-PCR and almost consistent with their Reads Per kb per Million values. These findings would provide useful references for improving the yield and quality of C. songaricum.

Functional R2R3-MYB Transcription Factor NsMYB1, Regulating Anthocyanin Biosynthesis, Was Relative To The Fruit Color Differentiation in Nitraria Sibirica Pall

Background Nitraria sibirica Pall. is an economic plant with two kinds of fruit color, widely spreads in the Qinghai Tibet Plateau. The chemical analysis and pharmacological evaluation had been carried out for several tens of years, the mechanism behind the fruit color differentiation is still unclear. Results In this manuscript, the chemical analysis of the extractions showed that the chemical composition of fruit color was anthocyanin, and two kind of Nitraria sibirica Pall. were caused by the content differentiation with the same anthocyanin kinds. Cya-nidin-3-[2ʹ’-(6ʹ’’-coumaroyl)-glucosyl]-glucoside (C3G) was the major anthocyanin. Transcriptome analysis and the qRT-PCR revealed that the structural genes relative to anthocyanin biosynthesis except CHS, F3’5’H and ANS were up-regulated in BF compared with RF, which indicated that transcript factor should be the reason for the expression difference of the structure genes. In the unigenes of the transcript factor MYB and bHLH, relative to anthocyanin, only NsMYB1 (Clus-ter-8422.10600), was high-expression and up-expression in the BF. NsMYB1 encoded the same length protein with four amino acid differences in the RF and BF, and both contained the intact DNA, HTH-MYB and SANT domains. NsMYB1 was close to the AtMYB114, AtMYB113 and AtPAP1, regulating anthocyanin biosynthesis, in phylogenetic relationship. Both NsMYB1r and NsMYB1b could promote the transcript of the structural genes, and induced the anthocyanin accumulation in all tissues of transgenic tobacco. The insertion of ‘TATA’ in the promoter of NsMYB1r gave one more promoter region, and was the reason for higher transcripts in black fruit possibly. Conclusions NsMYB1 was a functional R2R3-MYB transcription factor, regulated the anthocyanin biosynthesis, and leaded to the fruit color differentiation in Nitraria sibirica Pall.

Comprehensive transcriptome and metabolome profiling reveal metabolic mechanisms of Nitraria sibirica Pall. to salt stress

Nitraria sibirica Pall., a typical halophyte that can survive under extreme drought conditions and in saline-alkali environments, exhibits strong salt tolerance and environmental adaptability. Understanding the mechanism of molecular and physiological metabolic response to salt stress of plant will better promote the cultivation and use of halophytes. To explore the mechanism of molecular and physiological metabolic of N. sibirica response to salt stress, two-month-old seedlings were treated with 0, 100, and 400 mM NaCl. The results showed that the differentially expressed genes between 100 and 400 mmol L−1 NaCl and unsalted treatment showed significant enrichment in GO terms such as binding, cell wall, extemal encapsulating structure, extracellular region and nucleotide binding. KEGG enrichment analysis found that NaCl treatment had a significant effect on the metabolic pathways in N. sibirica leaves, which mainly including plant-pathogen interaction, amino acid metabolism of the beta alanine, arginine, proline and glycine metabolism, carbon metabolism of glycolysis, gluconeogenesis, galactose, starch and sucrose metabolism, plant hormone signal transduction and spliceosome. Metabolomics analysis found that the differential metabolites between the unsalted treatment and the NaCl treatment are mainly amino acids (proline, aspartic acid, methionine, etc.), organic acids (oxaloacetic acid, fumaric acid, nicotinic acid, etc.) and polyhydric alcohols (inositol, ribitol, etc.), etc. KEGG annotation and enrichment analysis showed that 100 mmol L−1 NaCl treatment had a greater effect on the sulfur metabolism, cysteine and methionine metabolism in N. sibirica leaves, while various amino acid metabolism, TCA cycle, photosynthetic carbon fixation and sulfur metabolism and other metabolic pathways have been significantly affected by 400 mmol L−1 NaCl treatment. Correlation analysis of differential genes in transcriptome and differential metabolites in metabolome have found that the genes of AMY2, BAM1, GPAT3, ASP1, CML38 and RPL4 and the metabolites of L-cysteine, proline, 4-aminobutyric acid and oxaloacetate played an important role in N. sibirica salt tolerance control. This is a further improvement of the salt tolerance mechanism of N. sibirica, and it will provide a theoretical basis and technical support for treatment of saline-alkali soil and the cultivation of halophytes.

Analysis of intraspecific polymorphism of Nitraria sibirica Pall. using the ISSR technique

The analysis of DNA polymorphism of Nitraria sibirica Pall. was carried out at 13 natural populations of the Republic of Altai and Altai Territory using the ISSR technique. Seven effective ISSR primers have been identified to analyze DNA polymorphism in N. sibirica. 99 DNA fragments were yielded at DNA amplification with these primers, 66 of them were polymorphic. The genetic distance Nei (D) between the studied populations of N. sibirica averaged 0.32, at mean 0.09 - within populations. An identification ISSR marker has been revealed, which can be used to study the genetic variability of the genus Nitraria L. (Nitrariaceae) species.

Biological features of Nitraria sibirica Pall. and the structure of its coenopopulation (the Republic of Khakasia)

The life form of Nitraria sibirica Pall. and the structure of its coenopopulation has been studied in natural conditions. Laboratory germination of seeds was investigated. Individuals build the life form of a hypogeogenic-geoxyle vegetative-mobile shrub. It is found that the coenopopulation is normal incomplete, the ontogenetic spectrum is of a centered type. The germination of seeds does not exceed 6 %.

Tissue tolerance mechanisms conferring salinity tolerance in a halophytic perennial species Nitraria sibirica Pall.

Plant salt tolerance relies on a coordinated functioning of different tissues and organs. Salinity tissue tolerance is one of the key traits that confers plant adaptation to saline environment. This trait implies maintenance low cytosolic Na+/K+ ratio in metabolically active cellular compartments. In this study, we used Nitraria sibirica Pall., a perennial woody halophytes species, to understand the mechanistic basis of its salinity tissue tolerance. The results showed that the growth of seedlings was stimulated by 100-200 mM NaCl treatment. The ions distribution analysis showed that the leaves acted as Na+ sink while plant root possess superior K+ retention. The excessive Na+ absorbed from soil was mainly transported to the shoot and eventually sequestrated into mesophyll vacuoles in the leaves. As a result, N. sibirica could keep optimal balance of K+/Na+ at a tissue- and cell-specific level under saline condition. To enable this, N. sibirica increased both vacuolar H+-ATPase and H+-PPase enzymes activities and up-regulated expressions of NsVHA, NsVP1 and NsNHX1 genes. Vacuolar Na+ sequestration in the leaf mesophyll mediated by NsVHA, NsVP1 and NsNHX1 reduced the Na+ concentration in cytosol and inhibited further K+ loss. Meanwhile, N.sibirica enhanced the TPK expression at the transcriptional level to promote K+ efflux from vacuole into cytoplasm, assisting in maintaining cytosolic K+ homeostasis. It is concluded that the tissue tolerance traits such as vacuolar Na+ sequestration and intracellular K+ homeostasis is critical to confer adaptation of N. sibirica to soil salinity.

Insights into Comparative Genomics, Codon Usage Bias, and Phylogenetic Relationship of Species from Biebersteiniaceae and Nitrariaceae Based on Complete Chloroplast Genomes

Biebersteiniaceae and Nitrariaceae, two small families, were classified in Sapindales recently. Taxonomic and phylogenetic relationships within Sapindales are still poorly resolved and controversial. In current study, we compared the chloroplast genomes of five species (Biebersteinia heterostemon, Peganum harmala, Nitraria roborowskii, Nitraria sibirica, and Nitraria tangutorum) from Biebersteiniaceae and Nitrariaceae. High similarity was detected in the gene order, content and orientation of the five chloroplast genomes; 13 highly variable regions were identified among the five species. An accelerated substitution rate was found in the protein-coding genes, especially clpP. The effective number of codons (ENC), parity rule 2 (PR2), and neutrality plots together revealed that the codon usage bias is affected by mutation and selection. The phylogenetic analysis strongly supported (Nitrariaceae (Biebersteiniaceae + The Rest)) relationships in Sapindales. Our findings can provide useful information for analyzing phylogeny and molecular evolution within Biebersteiniaceae and Nitrariaceae.