Composition variation of agarwood-associated microbial communities from Aquilaria sinensis

Abstract

Agarwood, derived from Aquilaria sinensis and Aquilaria malaccensis, is of medicinal 5 and ecological value and religious importance as incense. The existing imbalance between short supply 6 and increasing demand of this product remains to be solved. Thus, the biologically artificial agarwood-7 inducing methods commonly called whole-tree agarwood-inducing techniques (agar-wit) have been 8 established to dramatically improve agarwood yield within a short period. However, several studies 9 reported a lower content of ethanol-soluble extractive in the agar-wit agarwood than in the natural 10 agarwood. To further understand the role of microorganisms in agarwood formation, we investigated 11 and contrasted the endophytic bacteria and fungi between different types of agarwood from A. sinensis 12 through high-throughput sequencing. Results showed that the same dominant phyla of bacteria 13 consisting of Proteobacteria, Actinobacteria, and Acidobacteria were shared by the natural agarwood 14 and agar-wit agarwood. Meanwhile, Ascomycota and Basidiomycota constituted the similar dominant 15 fungal phyla of these two kinds of agarwood. However, the principal microbial communities at the 16 genus or order level evidently varied from natural agarwood to agar-wit agarwood. Moreover, the 17 bacterial communities are closely connected with terpenoid and carbohydrate metabolism, which 18 indicated that the bacterial communities also play a vital role in agarwood formation. In conclusion, the 19 higher concentrated abundance of the dominant microbial communities in agar-wit agarwood than in 20 natural agarwood may promote agarwood formation, however, the low evenness of microbial 21 communities also lowers the content of ethanol-soluble extractive. 22KEYWORDS natural agarwood, agar-wit agarwood, high-throughput sequencing, bacterial diversity, 23 fungal diversity 24 * You-Wei Wang IMPORTANCE Agarwood has become an indispensable product in modern life because of medicinal 25 value, ecological and religious importance as incense. Nevertheless, the enormous demand for 26 agarwood markedly exceeds the supply because of the dramatically declining population of genus 27 Aquilaria. Agarwood formation occurring slowly and infrequently in a natural environment, so various 28 artificial techniques were developed to promote the formation of agarwood, such as the physical 29 methods and chemical methods. However, these techniques still are insufficient to compensate for the 30 agarwood shortage. In this case, a novel biological method called the whole-tree agarwood-inducing 31 technique (Agar-wit) induces agarwood production. However, several studies have shown that 32 agarwood harvested from biological technology contains lower content of ethanol-soluble extractive 33 compared with natural agarwood. So to further expose and understand the endophytic bacteria and 34 fungi in agarwood formation is important for the improvement of biological method. 35 INTRODUCTION 36Aquilaria sinensis (Lour.) Gilg (Thymelaeaceae) is mainly distributed in the ...

Progressive Vertical and Horizontal Phytocompound Changes during Agarwood Formation in Aquilaria sinensis after Geotrichum candidum Injection

“…A. sinensis can synthesize phytoalexins for immune defense to induce agarwood formation mainly in the parenchyma cells of the interxylary phloem and xylem rays through fungal mobility and plant transpiration [1,26]. In early wounding, A. sinensis stimulates a wound-responsive gene to activate the octadecanoid pathway and jasmonate synthesis [7].…”

“…Chromones and sesquiterpenes have a high polarity index and are easier to elute in water through transpiration [47]. Microbial invasion occurred in the lower part of the tree and spread to the entire tree, possibly through transpiration [1]. The injection of G. candidum leads A. sinensis to synthesize secondary metabolites to suppress microbial attack and then causes necrosis of the host cells [48].…”

“…Agarwood is a blackish resinous heartwood on the trunk and branches of the entire tree [1], mainly from the genera Aquilaria and Gyrinops [2][3][4][5][6]. Agarwood accounts for 7-10% of the resin in Aquilaria trees [7].…”