Root Endophytes and Ginkgo biloba Are Likely to Share and Compensate Secondary Metabolic Processes, and Potentially Exchange Genetic Information by LTR-RTs

Abstract

Ginkgo biloba is a pharmaceutical resource for terpenes and flavonoids. However, few insights discussed endophytes’ role in Ginkgo, and whether genetic exchange happens between Ginkgo and endophytes remains unclear. Herein, functional gene profiles and repetitive sequences were analyzed to focus on these issues. A total of 25 endophyte strains were isolated from the Ginkgo root and distributed in 16 genera of 6 phyla. Significant morphological diversities lead to the diversity in the COG functional classification. KEGG mapping revealed that endophytic bacteria and fungi potentially synthesize chalcone, while endophytic fungi might also promote flavonoid derivatization. Both bacteria and fungi may facilitate the lignin synthesis. Aspergillus sp. Gbtc_1 exhibited the feasibility of regulating alcohols to lignans. Although Ginkgo and the endophytes have not observed the critical levopimaradiene synthase in ginkgolides synthesis, the upstream pathways of terpenoid precursors are likely intact. The MVK genes in Ginkgo may have alternative non-homologous copies or be compensated by endophytes in long-term symbiosis. Cellulomonas sp. Gbtc_1 became the only bacteria to harbor both MEP and MVA pathways. Endophytes may perform the mutual transformation of IPP and DMAPP in the root. Ginkgo and bacteria may lead to the synthesis and derivatization of the carotenoid pathway. The isoquinoline alkaloid biosynthesis seemed lost in the Ginkgo root community, but L-dopa is more probably converted into dopamine as an essential signal-transduction substance. So, endophytes may participate in the secondary metabolism of the Ginkgo in a shared or complementary manner. Moreover, a few endophytic sequences predicted as Ty3/Gypsy and Ty1/Copia superfamilies exhibited extremely high similarity to those of Ginkgo. CDSs in such endophytic LTR-RT sequences were also highly homologous to one Ginkgo CDS. Therefore, LTR-RTs may be a rare unit flowing between the Ginkgo host and endophytes to exchange genetic information. Collectively, this research effectively expanded the insight on the symbiotic relationship between the Ginkgo host and the endophytes in the root.

The novel distribution of intracellular and extracellular flavonoids produced by Aspergillus sp. Gbtc 2, an endophytic fungus from Ginkgo biloba root

“…If the MEP pathway of Ginkgo comes from an endosymbiotic prokaryote as widely accepted, the MVK gene involved in the original MVA pathway of Ginkgo may have a non-highly-homologous replaceable copy, or it may be compensated by endophytes due to a long-term symbiotic relationship, like Cellulomonas sp. Gbtc_1 ( Zou et al, 2021 ). Endophytic fungi were the production source of many known or unknown new bioactive metabolites ( Queiroz and Santana, 2020 ; Aftab et al, 2021 ; Bezerra et al, 2021 ).…”

“…Streptomyces sp. Gbtc 1 was also shown to contain genes for key functional enzymes in synthesis pathway of natural products and local secondary metabolites similar to Ginkgo host ( Zou et al, 2021 ). Mucor circinelloides DF20 has been reported to promote biosynthesis and accumulation of tanshinone in Salvia miltiorrhiza ( Chen et al, 2021 ).…”

Endophytic Bacterial Communities of Ginkgo biloba Leaves During Leaf Developmental Period

“…The washed fresh leaves were ground in liquid nitrogen, and 200 mg of the ground powder in liquid nitrogen was added to 30 ml of 70% ethanol, vortexed and homogenized for 1 min, and then subjected to an hour ultrasonic extraction for the flavonoids according to research ( Zou et al, 2021 ). The mixture was centrifuged at 13,000 rpm for 10 min at 4°C and then 1 ml of the supernatant was dried in nitrogen at 37°C.…”

Using Next-Generation Sequencing Technology to Explore Genetic Pathways in Endophytic Fungi in the Syntheses of Plant Bioactive Metabolites

“…4.6.6. Polyphenols, Flavonoids, Terpenoids, Isoquinoline Alkaloids An interesting attempt towards elucidation of multiple pathway genes was made recently by Zou et al [83]. The maidenhair tree (Ginkgo biloba) is a natural resource for flavonoids and terpenes.…”

“…Furthermore, there are more and more examples of using the advantages of the third-generation technology in the field of fungal genomics. The accurate long-read sequences obtained through the PacBio Sequel Systems were used to assemble the draft genomes of fungal endophytes isolated from G. biloba [83]. The genome of an endophytic strain of Amphirosellinia nigrospora (JS-1675), isolated from Pteris cretica, was recently sequenced with the PacBio RS II technology [106].…”