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.
Highlights
Ever since discovering and separating microorganisms, humanity has opened a new world of cognition and scientific research
After the suspected same species were selectively abandoned according to the colonies’ morphology (Supplementary Figure 1) and the blast results of the 16s rDNA and internal transcribed spacer (ITS) sequences (Supplementary File 1), 23 bacterial strains and 2 fungal strains were chosen to be used for the subsequent genome sequencing and bioinformatics analysis
As aromatic-L-amino-acid/Ltryptophan decarboxylase (K01593) became the sole enzyme we identified in the indole alkaloid biosynthesis of this root community; detailed insight was excavated to the biosynthesis of isoquinoline alkaloid
Summary
Ever since discovering and separating microorganisms, humanity has opened a new world of cognition and scientific research. In terms of life strategies, these endophytes can be classified into obligate and facultative ones (Hardoim et al, 2008). The obligate endophytes strictly rely on the plant host to grow and survive, and they are transmitted vertically or by carriers. Facultative endophytes refer to the ones that enter the plant at a particular life stage and gradually survive and persist in the host. The rhizobia are the representative facultative endophytes, and they are considered to be derived from soil and invade plant cells or tissues through cracks at the fibrous root junction (Chi et al, 2005). Root crack may be the primary approach for endophytes colonization; notwithstanding, other entries into the plant host still exist, like stomata on leaf tissue and physical trauma (McCully, 2001)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
