Fungal endophytes of Taxus species and regulatory effect of two strains on taxol synthesis

Abstract

Background: Taxol, derived from Taxus trees, is a valuable natural resource for the development of anticancer drugs. Endophytic fungi from Taxus trees are a promising alternative source of Taxol. However, the impact of plant-endophytic microbial interaction on the host's Taxol biosynthesis is largely unknown.

Results: In the current study, the diversity of endophytic fungi in three different Taxus species was analyzed using Internal Transcribed Spacer sequencing. A total of 271 Operational Taxonomic Units (OTUs) were identified, grouping into 2 phyla, 8 classes, 16 orders, 19 families, and 19 genera. Alpha and beta diversity analysis indicated significant differences in endophytic fungal communities among the various Taxus trees. At the genus level, Alternaria and Davidiella were predominantly found in T. mairei and T. media, respectively. By utilizing a previously published dataset, a Pearson correlation analysis was conducted to predict the taxol biosynthesis-related fungal genera. Following screening, two isolates of Alternaria (L7 and M14) were obtained. Effect of inoculation with Alternaria isolates on the gene expression and metabolite accumulation of T. mairei was determined by transcriptomic and untargeted metabolomic studies. The co-inoculation assay suggests that the two Alternaria isolates may have a negative regulatory effect on taxol biosynthesis by influencing hormone signaling pathways.

Conclusion: Our findings will serve as a foundation for advancing the production and utilization of Taxus and will also aid in screening endophytic fungi related to taxol production.

Keywords: Taxus; Correlation analysis; Diversity; Endophytic fungi; ITS sequencing.

Fig. 1

Overview of the sequencing data. (a) The length of all tags. (b) Venn diagram shows the OTUs shared by T. cuspidate, T. mairei, and T. media samples. (c) A heatmap of the abundance of OTU in the three Taxus species (N = 15). The heatmap scale ranges from 0 to 25 on a log2 scale

Fig. 2

Alpha diversity analysis. Four parameters, including (a) Rarefaction: Chao1 index curve, (b) Rarefaction: Observed_species index curve, (c) Dendrogram analysis and (d) PCA, were analyzed

Fig. 3

Taxonomic analysis of endophytic fungal communities. (a) Taxonomic analysis of endophytic fungi at phylum level. (b) Taxonomic analysis of endophytic fungi at class level. (c) Taxonomic analysis of endophytic fungi at genus level

Fig. 4

Pearson correlation analysis of differential fungal genus and host’s taxoid accumulation levels. Analysis of paclitaxel (a), 3’-N-debenzoyltaxol (b), 3’-N-debenzoyl-2’-deoxytaxol (c), 10-deacetyl-2-debenzoylbaccatin III (d), baccatin III (e), and 10-deacetylbaccatin III (f)-related differential fungal genus

Fig. 5

Screening of taxol biosynthesis-related fungal isolates. (a) The relative abundance level of Alternaria genus in three different Taxus species. (b) Pearson correlation analysis of differential fungal genus and host’s taxoid accumulation levels. (c) Photograph of two fungal isolates belonging to Alternaria genus. (d) Phylogenetic relationships of Alternaria isolates L7 and M14 with other Alternaria spp. based on the ITS sequences. Red stars indicated Alternaria isolates L07 and M14

Fig. 6

Effect of inoculation withAlternariaisolates L7 and M14 on the host Taxus trees. (a) The spores of Alternaria isolate L7 and M14 was sprayed onto the twigs of T. mairei. (b) The number of up-regulated and down-regulated genes after Alternaria isolate L7 and M14 spore infection. (c) GO enrichment analysis of the DEGs after Alternaria isolate L7 and M14 spore infection. (d) The expression level of taxol biosynthesis pathway genes after Alternaria isolate L7 and M14 spore infection. Red indicated up-regulated genes and green indicated down-regulated genes. The heatmap scale ranges from − 2 to + 2 on a log2 scale. (e) The number of phytohormone-related DEGs. Red indicated up-regulated genes and green indicated down-regulated genes

Fig. 7

Effect of inoculation with Alternaria isolate on the metabolite accumulation of T. mairei. Relative accumulation levels of four taxoids and seven hormones. Each value is the mean ± standard deviation of three biological repeats. *P < 0.05