AUTHOR=Zhao Yongxia , Ji Xiaolong , Liu Xiaoqi , Qin Lin , Tan Daopeng , Wu Di , Bai Chaojun , Yang Jiyong , Xie Jian , He Yuqi 

TITLE=Age-dependent dendrobine biosynthesis in Dendrobium nobile: insights into endophytic fungal interactions

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1294402

DOI=10.3389/fmicb.2023.1294402

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p><italic>Dendrobium nobile (D. nobile)</italic>, a valued Chinese herb known for its diverse pharmacological effects, owes much of its potency to the bioactive compound dendrobine. However, dendrobine content varies significantly with plant age, and the mechanisms governing this variation remain unclear. This study delves into the potential role of endophytic fungi in shaping host-microbe interactions and influencing plant metabolism.</p></sec><sec><title>Methods</title><p>Using RNA-seq, we examined the transcriptomes of 1-year-old, 2-year-old, and 3-year-old <italic>D. nobile</italic> samples and through a comprehensive analysis of endophytic fungal communities and host gene expression in <italic>D. nobile</italic> stems of varying ages, we aim to identify associations between specific fungal taxa and host genes.</p></sec><sec><title>Results</title><p>The results revealing 192 differentially expressed host genes. These genes exhibited a gradual decrease in expression levels as the plants aged, mirroring dendrobine content changes. They were enriched in 32 biological pathways, including phagosome, fatty acid degradation, alpha-linolenic acid metabolism, and plant hormone signal transduction. Furthermore, a significant shift in the composition of the fungal community within <italic>D. nobile</italic> stems was observed along the age gradient. <italic>Olipidium</italic>, <italic>Hannaella</italic>, and <italic>Plectospherella</italic> dominated in 1-year-old plants, while <italic>Strelitziana</italic> and <italic>Trichomerium</italic> prevailed in 2-year-old plants. Conversely, 3-year-old plants exhibited additional enrichment of endophytic fungi, including the genus <italic>Rhizopus</italic>. Two gene expression modules (mediumpurple3 and darkorange) correlated significantly with dominant endophytic fungi abundance and dendrobine accumulation. Key genes involved in dendrobine synthesis were found associated with plant hormone synthesis.</p></sec><sec><title>Discussion</title><p>This study suggests that the interplay between different endophytic fungi and the hormone signaling system in <italic>D. nobile</italic> likely regulates dendrobine biosynthesis, with specific endophytes potentially triggering hormone signaling cascades that ultimately influence dendrobine synthesis.</p></sec>