Fe induced a dynamic and biased allocation of material flux within terpenoid metabolism is controlled by CbNudix in Conyza blinii

Conyza Blinii (C. blinii) is a unique traditional Chinese medicine growing in Sichuan, China, which has soils with an abundant iron content. This Fe enrichment environment contributed to a variety of terpenoids of C. blinii, blinin and saponin which can play an important role in the process of resisting abiotic stress. The relationship between Fe and terpenoid metabolism was studied to explore Fe tolerance mechanism of C. blinii. In this study, C. blinii was treated with ferrous iron solutions, and the effect of ferrous iron on the synthesis of blinin and saponins was further studied by spectrophotometry and liquid chromatography. Also, gene expression was detected by qRT-PCR. Under ferrous treatment, the blinin content of C. blinii increased, while the total saponin content decreased. When the ferrous concentration reached 200 μM, the difference in metabolite production was the largest. Furthermore, it was found that blinin and saponin have synchronous and opposite accumulation trends, accompanied by time dependence. The genes expression results of key enzyme in the MVA and MEP pathways showed the same trends. In this process, the expression of CbNudixs played a key role to switch the material flux between MVA and MEP, via catalyzed the dephosphorylation of isoprenoid diphosphate. This study explored the effect of ferrous iron on the saponin and blinin synthesis of C. blinii and found the unique role of CbNudixs in regulating material flux between diterpene and triterpene synthesis, which greatly deepened our understanding of the mechanism of Fe tolerance of C. blinii.

Origin and Evolution of Polycyclic Triterpene Synthesis

Polycyclic triterpenes are members of the terpene family produced by the cyclization of squalene. The most representative polycyclic triterpenes are hopanoids and sterols, the former are mostly found in bacteria, whereas the latter are largely limited to eukaryotes, albeit with a growing number of bacterial exceptions. Given their important role and omnipresence in most eukaryotes, contrasting with their scant representation in bacteria, sterol biosynthesis was long thought to be a eukaryotic innovation. Thus, their presence in some bacteria was deemed to be the result of lateral gene transfer from eukaryotes. Elucidating the origin and evolution of the polycyclic triterpene synthetic pathways is important to understand the role of these compounds in eukaryogenesis and their geobiological value as biomarkers in fossil records. Here, we have revisited the phylogenies of the main enzymes involved in triterpene synthesis, performing gene neighborhood analysis and phylogenetic profiling. Squalene can be biosynthesized by two different pathways containing the HpnCDE or Sqs proteins. Our results suggest that the HpnCDE enzymes are derived from carotenoid biosynthesis ones and that they assembled in an ancestral squalene pathway in bacteria, while remaining metabolically versatile. Conversely, the Sqs enzyme is prone to be involved in lateral gene transfer, and its emergence is possibly related to the specialization of squalene biosynthesis. The biosynthesis of hopanoids seems to be ancestral in the Bacteria domain. Moreover, no triterpene cyclases are found in Archaea, invoking a potential scenario in which eukaryotic genes for sterol biosynthesis assembled from ancestral bacterial contributions in early eukaryotic lineages.

The Influence of Auxins on the Biosynthesis of Isoprene Derivatives in Callus Cultures of Vaccinium corymbosum var. bluecrop

Callus cultures of Vaccinium corymbosum var. bluecrop were optimized for their isoprene derivatives production by supplementing Schenk-Hildebrandt (SH) medium with constant concentration of kinetin (2.32 μᴍ) and two different amounts of selected auxins. Every auxin, except for IBA, used in 10-time higher concentration (2,4D, NAA, IAA, NOA) stimulated biosynthesis of β-sitosterol and inhibited triterpene synthesis. Quantitative analysis of isoprene derivatives in callus biomass collected on the 25th day of the experiment proved that the analyzed callus of Vaccinium corymbosum var. bluecrop synthesized the highest amount of isoprene derivatives after subculturing on SH medium modified with 22.6 μᴍ of 2,4D and 2.32 μᴍ of kinetin.