Comparative transcriptome analysis to identify putative genes involved in carvacrol biosynthesis pathway in two species of Satureja, endemic medicinal herbs of Iran.

Satureja is rich in phenolic monoterpenoids, mainly carvacrol, that is of interest due to diverse biological activities including antifungal and antibacterial. However, limited information is available regarding the molecular mechanisms underlying carvacrol biosynthesis and its regulation for this wonderful medicinal herb. To identify the putative genes involved in carvacrol and other monoterpene biosynthesis pathway, we generated a reference transcriptome in two endemic Satureja species of Iran, containing different yields (Satureja khuzistanica and Satureja rechingeri). Cross-species differential expression analysis was conducted between two species of Satureja. 210 and 186 transcripts related to terpenoid backbone biosynthesis were identified for S. khuzistanica and S. rechingeri, respectively. 29 differentially expressed genes (DEGs) involved in terpenoid biosynthesis were identified, and these DEGs were significantly enriched in monoterpenoid biosynthesis, diterpenoid biosynthesis, sesquiterpenoid and triterpenoid biosynthesis, carotenoid biosynthesis and ubiquinone and other terpenoid-quinone biosynthesis pathways. Expression patterns of S. khuzistanica and S. rechingeri transcripts involved in the terpenoid biosynthetic pathway were evaluated. In addition, we identified 19 differentially expressed transcription factors (such as MYC4, bHLH, and ARF18) that may control terpenoid biosynthesis. We confirmed the altered expression levels of DEGs that encode carvacrol biosynthetic enzymes using quantitative real-time PCR (qRT-PCR). This study is the first report on de novo assembly and transcriptome data analysis in Satureja which could be useful for an understanding of the main constituents of Satureja essential oil and future research in this genus.

Selenium Nanoparticles (Se-NPs) Alleviates Salinity Damages and Improves Phytochemical Characteristics of Pineapple Mint (Mentha suaveolens Ehrh.).

The present study examined the effects of foliar spray of selenium nanoparticles (0, 10 and 20 mg/L) on the yield, phytochemicals and essential oil content and composition of pineapple mint (Mentha suaveolens Ehrh.) under salinity stress (0, 30, 60 and 90 mM NaCl). Obtained results demonstrated that severe salinity stress reduced the fresh weight (FW) and plant height (PH) by 16.40% and 19.10%, respectively compared with normal growth condition. On the other hands, under sever salinity stress relative water content (RWC) and chlorophyll index were reduced by 18.05% and 3.50%, respectively. Interestingly, selenium nanoparticles (Se-NPs; 10 mg/L) application improved the pineapple mint growth. Based on GC-FID and GC-MS analysis, 19 compounds were identified in pineapple mint essential oil. Foliar application of Se-NPs and salinity did not change the essential oil content of pineapple mint, however, the essential oil compounds were significantly affected by salinity and Se-NPs- applications. Foliar application of Se-NPs- had a significant effect on piperitenone oxide, limonene, jasmone, viridiflorol and ß-myrsene under different salinity levels. The highest percentage of piperitenone oxide (79.4%) as the major essential oil component was recorded in the no salinity treatment by applying 10 mg/L of nanoparticle. Interestingly, application of 10 mg L-1 Se-NPs- under 60 mM NaCl increased the piperitenone oxide content by 9.1% compared with non-sprayed plants. Finally, the obtained results demonstrated that foliar application of Se-NPs (10 mg L-1) can improve the pineapple mint growth and secondary metabolites profile under saline conditions.

Natural diversity in phenolic components and antioxidant properties of oregano (Origanum vulgare L.) accessions, grown under the same conditions.

Oregano (Origanum vulgare L.) is a rich source of biologically active components such as phenolic compounds. Here, seven pot grown O. vulgare accessions belonging to three subspecies (subsp. virens, subsp. vulgare and subsp. gracile) were investigated for their content in sixteen bioactive phenolic compounds as well as their antioxidant capacities (DPPH• and FRAP tests), total phenolic content (TPC) and total flavonoid content (TFC) in order to identify the most suitable ones on an industrial level. HPLC analyses showed that rosmarinic acid (659.6-1646.9 mg/100 g DW) was by far the most abundant constituent, followed by luteolin (46.5-345.4 mg/100 g DW), chicoric acid (36.3-212.5 mg/100 g DW), coumarin (65.7-193.9 mg/100 g DW) and quercetin (10.6-106.1 mg/100 g DW), with variability in concentration depending on the accession and subspecies. The highest level of rosmarinic acid and TPC was obtained from Ardabil accession (subsp. virens). There was a significant and positive correlation between rosmarinic acid and antioxidant activity (r = 0.46). TFC significantly correlated to TPC (r = 0.57) as well as to chicoric acid (r = 0.73). Cluster (CA) and principal component (PCA) analyses classified the investigated accessions in three different groups. Such natural variabilities in phenolics provide the possibility of using elite plants for nutraceutical and pharmaceutical industries and domestication of highly antioxidative accessions of oregano.

Improvement of Growth, Yield, Seed Production and Phytochemical Properties of Satureja khuzistanica Jamzad by Foliar Application of Boron and Zinc.

Satureja khuzistanica Jamzad is a valuable and endemic medicinal plant. Boron and zinc are essential elements for the vegetative and reproductive growth of plants and have significant effects on yield, essential oil composition and the seed production of plants. To investigate the effects of the foliar application of zinc and boron on the growth, yield, seed production and phytochemical properties of S. khuzistanica, a study was conducted in a factorial experiment with three replicates in two consecutive years based on a randomized complete block design. The foliar application of boron (B) at three concentrations (control or distilled water, 0.4% and 0.8% as H3BO3) and zinc (Zn) at three concentrations (control or distilled water, 0.3% and 0.6% as ZnSO4) was carried out. Our results showed that the foliar application of B resulted in a significant increase in the fresh and dry weights of plants, the dry weight of stems, drug yield, seed yield, seed germination and 1000-seed weight. At the same time, the application of B resulted in a significant decrease in seed emptiness. The fresh and dry weights of plants, drug yield, seed yield, 1000-seed weight and seed germination were also significantly improved by Zn foliar spraying compared to the control. Application of 0.8% B resulted in a significant decrease in seed emptiness by 14.16% and 22.37%, as compared to the control. The foliar spraying of B and Zn improved the total phenolic content, the essential oil content and the yield and antioxidant activity of S. khuzistanica. Moreover, B application generally concentrated more carvacrol in the essential oil (in the first experimental year). In contrast, no significant differences were observed between Zn treatments in carvacrol content and total flavonoids. The use of several microelements, such as B and Zn, could improve both the quantity and quality of S. khuzistanica. Additionally, improvement of seed set and seed quality by the foliar spraying of Zn and B may be useful for growing plants in arid and semi-arid areas.

Screening of tarragon accessions based on physiological and phytochemical responses under water deficit.

In this study, screening of Artemisia dracunculus accessions was investigated under water deficit based on physiological and phytochemical traits. The results clearly indicated that water deficit significantly reduced the relative water content, chlorophyll, and carotenoid contents and increased malondialdehyde, electrolyte leakage, and antioxidant activities. The responses of tarragon accessions to water deficit, however, were inconsistent. The HPLC analysis revealed the presence of chlorogenic, syringic, ferulic, vanillic, chicoric, and p-coumaric acids as major phenolic acids, while quercetin and herniarin were detected as the predominant flavonoid and coumarin compounds in the extracts. Our findings revealed that the water deficit not only increased the amounts of herniarin, luteolin, apigenin, caffeic acid, and syringic acid, but also introduced quercetin that was not present under normal conditions in Estahbanat. Nevertheless, these results were highly impacted by the accession type. The results indicated that Hamadan, Varamin and Estahbanat accessions could be introduced as tolerant accessions. Given the very different responses of tarragon accessions to water deficit and the diversity between these accessions, the findings of the present study could be an effective step in identifying and achieving homogeneous, drought-tolerant and high-yield potential accessions, and may help tarragon breeding programs as well as development of cultivation.