Physiological and Transcriptomic Analysis Provide Insight into Low Temperature Enhancing Hypericin Biosynthesis in Hypericum perforatum

Abstract

Hypericin (Hyp), well-known as an antidepressant, is mainly extracted from Hypericum perforatum. Although Hyp accumulation and biomass are greater at lower compared to higher temperature, the regulation mechanism has not been reported. Here, the physiological characteristics and transcriptome of H. perforatum grown at 15 and 22 °C were determined and analyzed by HPLC and de novo sequencing. The results showed that the stomatal density and opening percentages were 1.1- and 1.4-fold more, and the Hyp content was 4.5-fold greater at 15 °C compared to 22 °C. A total of 1584 differentially expressed genes (DEGs) were observed at 15 versus 22 °C, with 749 characterized genes, 421 upregulated (UR) and 328 downregulated (DR). Based on biological functions, 150 genes were associated with Hyp biosynthesis, plant growth and the stress response, including photosynthesis, carbohydrate metabolism, fatty acids metabolism, cytochrome P450 (CYPs), morpho-physiological traits, heat shock proteins (HSPs), cold-responsive proteins (CRPs) and transcription factors (TFs). The differential expression levels of the master genes were confirmed by qRT-PCR and almost consistent with their Reads Per kb per Million (RPKM) values. This physiological and transcriptomic analyses provided insight into the regulation mechanisms of low temperature enhancing Hyp biosynthesis in H. perforatum.

Low temperature modifies seedling leaf anatomy and gene expression in Hypericum perforatum

“…A 1.1- and 1.2-fold increase of chlorophyll (a + b) and carotenoid contents was observed at 15 compared with 22°C, respectively ( Figure S4 ). These results were consistent with previous reports that low temperature can significantly increase chlorophyll content, plant growth and subsequently enhance biomass accumulation in comparison with high temperatures (22 and 30°C) ( Yao et al., 2019 ; Su et al., 2021 ). Five photosynthetic encoded genes ( i.e.…”

“…H. perforatum seedlings were grown from seed [collected Kangxian county (33°16′20″N, 105°31′50″E; 1050 m a.s.l.) located in Gansu province, China] and acclimated to defined temperatures according to previously published protocols ( Yao et al., 2019 ; Su et al., 2021 ). Specifically, seeds were successively disinfected with 70% ethanol (v/v) and 0.1% HgCl 2 (w/v), and then the sterilized seeds were inoculated on Murashige and Skoog (MS) + 20.0 g/L sucrose + 4.0 g/L agar (pH 5.8) and germinated at 22°C (24 h/d photoperiod, white light, 500 µmol·m −2 ·s −1 Flux; 50 ± 5% relative humidity).…”

“…RNA sequencing was by unigene expression analysis and basic annotation was conducted; 1584 high-level expressed genes with 749 characterized genes and 150 genes involved in plant growth, Hyp biosynthesis and environmental response have been identified with |log 2 (fold-change)| > 1 in previously published article ( Su et al., 2021 ). In this study, low-level genes were identified according to a criteria of 0.2< |log 2 (fold-change)|< 1.0 ( Robinson et al., 2009 ; Love et al., 2014 ), since low-level genes also play important roles in many biological processes ( Maia et al., 2007 ; Gotor et al., 2010 ).…”

“…Previous studies have found that ca. 750 genes are differentially expressed and 150 genes are involved in plant growth, Hyp biosynthesis and/or environmental responses in H. perforatum seedlings at different temperatures ( Su et al., 2021 ). Based on this previous study, St John’s wort expression levels for low-level gene candidates have been quantified by qRT-PCR (real time quantitative PCR), to further probe the mechanism of seedlings performance under a cool temperature.…”

Cool Temperature Enhances Growth, Ferulic Acid and Flavonoid Biosynthesis While Inhibiting Polysaccharide Biosynthesis in Angelica sinensis

“…The accumulation of plant secondary metabolites is often affected by environmental factors, such as light, water and temperature [ 29 ]. Low temperatures are one of the most important factors regulating phenylpropanoid metabolism [ 30 ]. Both ferulic acid and flavonoid biosynthesis pathways belong to the phenylpropanoid metabolism and employ the same genes, PAL , C4H and 4CL ( Figure 1 ).…”