Functional Insights into the Roles of Hormones in the Dendrobium officinale-Tulasnella sp. Germinated Seed Symbiotic Association

作   者：Tao Wang, Zheng Song, Xiaojing Wang, Lijun Xu, Qiwu Sun, Lubin Li.
期刊名称：International Journal of Molecular Sciences
影响因子：3.687
卷 期 号：19(11)
页     码：3484
关键词：Dendrobium officinale; Tulasnella sp.; symbiosis; endogenous hormones
论文摘要：
Abstract: Dendrobium is one of the largest genera in the Orchidaceae, and D. officinale is used in
traditional medicine, particularly in China. D. officinale seeds are minute and contain limited
energy reserves, and colonization by a compatible fungus is essential for germination under
natural conditions. When the orchid mycorrhizal fungi (OMF) initiates symbiotic interactions with
germination-driven orchid seeds, phytohormones from the orchid or the fungus play key roles, but
the details of the possible biochemical pathways are still poorly understood. In the present study, we
established a symbiotic system between D. officinale and Tulasnella sp. for seed germination. RNA-Seq
was used to construct libraries of symbiotic-germinated seeds (DoTc), asymbiotic-germinated seeds
(Do), and free-living OMF (Tc) to investigate the expression profiles of biosynthesis and metabolism
pathway genes for three classes of endogenous hormones: JA (jasmonic acid), ABA (abscisic acid)
and SLs (strigolactones), in D. officinale seeds and OMF under symbiotic and asymbiotic conditions.
Low concentrations of endogenous JA, ABA, or SLs were detected in the D. officinale-Tulasnella
symbiont compared with the asymbiotic tissues. Gene annotation results suggest that the expression
of DEGs (differentially expressed genes) related to JA and ABA biosynthesis from D. officinale were
down-regulated, while most of the key DEGs related to SL biosynthesis from D. officinale were
up-regulated in the symbiotic germinated seeds compared with the asymbiotic germinated seeds.
Moreover, in the OMF, we found a significantly up-regulated differential expression of the JA and
ABA biosynthesis-related genes in the symbiotic interaction, with the opposite expression trends
to those found in Dendrobium. This indicates that Dendrobium seed symbiotic germination may be
stimulated by the apparent involvement of the OMF in the production of hormones, and relatively
low concentrations of endogenous JA, ABA, or SLs might be maintained to promote the growth of the
D. officinale-Tulasnella symbiotic protocorm-like body. These results will increase our understanding of
the possible roles played by endogenous hormones in the regulation of the orchid-fungus symbiosis.