Diversity and bioactivities of fungal endophytes from Distylium chinense, a rare waterlogging tolerant plant endemic to the Three Gorges Reservoir [post]

2019 unpublished
The present study focuses on diversity and biological activities of the endophytic fungal community from Distylium chinense , a rare waterlogging tolerant plant endemic to the Three Gorges Reservoir. This study has been explored the characteristics of endophytic fungi in waterlogged environment including both aquatic and terrestrial fungi, and they may produce new metabolites under complex and extreme conditions, which may possess bioactive property. Therefore, the antioxidant, antimicrobial
more » ... t, antimicrobial and anticancer activities of all endophytes isolated from this study have been investigated. Moreover, the active metabolites of the most broad-spectrum bioactive strain have also been studied. Results A total of 154 fungal endophytes were isolated from roots and stems. They were categorized into 30 morphotypes based on cultural characteristics and were affiliated with 27 different taxa. Among these, the most abundant fungal orders included Diaporthales (34.4%) and Botryosphaeriales (30.5%), which were predominantly represented by the species Phomopsis sp. (24.7%) and Neofusicoccum parvum (23.4%). Fermentation extracts were evaluated, screening for antioxidant, antimicrobial and anticancer activities. Among the 154 isolates tested, 99 (64.3%) displayed significant antioxidant activity, 153 (99.4%) exhibited inclusive antimicrobial activity against at least one tested microorganism and 27 (17.5%) showed exclusive anticancer activity against one or more cancer cell lines. Specifically, the crude extract of Irpex lacteus DR10-1 exhibited note-worthy bioactivities. Further chemical investigation on DR10-1 strain resulted in the isolation and identification of two known bioactive metabolites, indole-3-carboxylic acid ( 1 ) and indole-3carboxaldehyde ( 2 ), indicating their potential roles in plant growth promotion and human medicinal value. Conclusions These results indicated that diverse endophytic fungal population inhabits D. chinense . The isolated endophyte DR10-1 ( Irpex lacteus ) has the potential to be a source of novel antioxidant/antimicrobial/anticancer compounds. The findings of the present study not only provide a sustainable resource for the utilization of endophytic fungi in D. chinense but also provides an important basis for further understanding of fungal communities in medicinal plants. 4 Background Endophytic fungi in plants are microorganisms that parasitize symbiotically in the internal tissues during the whole or part of their life cycles of the hosts without causing apparent pathogenic symptoms [1], but may turn pathogenic during host senescence [2]. Accumulated evidence has confirmed that plant endophytes from special orextreme environment has many effects on host ecological adaptability [3-5]. It is well known that the concurrence of endophytes may accelerate plant growth and increase the survival rate of biotic or abioticstresses, such as plant diseases, pests, drought, salinity and extreme temperatures [6-9]. Specifically, some endophytes are beneficial to plants by producing special substances, such as secondary metabolites, which can prevent the host from being attacked successfully by fungi and pests [10]. So far, endophytes, especially those under complex and extreme conditions, have been shown to produce a variety of metabolites with complex structures, such as alkaloids, terpenoids, polyketides, lipids, proteins, glycosides, isoprenoids, and hybrids of those metabolites, etc. [11-13]. More interestingly, these metabolites also showed a variety of interesting bioactivities including antifungal [14], antibacterial [15], anticancer [16], anti-HIV [17], antioxidants [18], etc. Due to these, endophytes from an untapped diverse habitat are a significant source of novel and natural drugs [19]. After Three Gorges Dam was constructed, the Three Gorges Reservoir (TGR) forms a new vast hydrofluctuation belt with an elevation of 145 m in summer to 175 m in winter, a length of more than 2000 km and an area of 300 km 2 [20, 21], it has formed unique ecological conditions for species diversity and biological distribution in the TGR area [22]. Many field surveys have shown that most of the predam riparian vegetation is gradually dying out due to the inability to adapt to the reversal of submergence time, the prolongation of flood duration and the new hydrological fluctuation zone (up to 30m in elevation) [23]. Generally, plants use limited oxygen and light under flood conditions, resulting in production of excessive reactive oxygen species (ROS) [24] , which were the key factors that hindered the growth and development of submerged plants [25, 26] . They are forced to undergo the oxidative pathway [27] , and usually develop an antioxidant defense system consisting of some antioxidant enzymes and specific metabolites to convert these excessive ROS into harmless products
doi:10.21203/rs.2.14491/v1 fatcat:oxrjpnbj3nb2hf23bclo65ak34