iTRAQ and RNA-Seq Analyses Provide New Insights into Regulation Mechanism of Symbiotic Germination of Dendrobium officinale Seeds (Orchidaceae)

Mycorrhizal fungi colonize orchid
seeds and induce germination.
This so-called symbiotic germination is a critical developmental process
in the lifecycle of all orchid species. However, the molecular changes
that occur during orchid seed symbiotic germination remain largely
unknown. To better understand the molecular mechanism of orchid seed
germination, we performed a comparative transcriptomic and proteomic
analysis of the Chinese traditional medicinal orchid Dendrobium
officinale to explore the change in protein expression at
the different developmental stages during asymbiotic and symbiotic
germination and identify the key proteins that regulate the symbiotic
germination of orchid seeds. Among 2256 identified plant proteins,
308 were differentially expressed across three developmental stages
during asymbiotic and symbiotic germination, and 229 were differentially
expressed during symbiotic germination compared to asymbiotic development.
Of these, 32 proteins were coup-regulated at both the proteomic and
transcriptomic levels during symbiotic germination compared to asymbiotic
germination. Our results suggest that symbiotic germination of D. officinale seeds shares a common signaling pathway with
asymbiotic germination during the early germination stage. However,
compared to asymbiotic germination, fungal colonization of orchid
seeds appears to induce higher and earlier expression of some key
proteins involved in lipid and carbohydrate metabolism and thus improves
the efficiency of utilization of stored substances present in the
embryo. This study provides new insight into the molecular basis of
orchid seed germination.

地衣真菌侵染兰科种子并诱导其发芽。所谓共生发芽，是所有兰科物种生命周期中的关键发育过程。然而，在兰科种子共生发芽过程中发生的分子变化仍然知之甚少。为了更好地理解兰科种子发芽的分子机制，我们对传统药用兰科植物铁皮石斛进行了比较转录组和蛋白质组分析，旨在探讨非共生和共生发芽不同发育阶段的蛋白质表达变化，并鉴定调控兰科种子共生发芽的关键蛋白。在识别的2256种植物蛋白中，有308种在非共生和共生发芽的三个发育阶段中表达差异，有229种在共生发芽期间与非共生发育相比表达差异。其中，有32种蛋白在共生发芽期间与非共生发芽相比，在蛋白质组和转录组水平上均受到协同调控。我们的结果表明，铁皮石斛种子的共生发芽在早期发芽阶段与共生发芽共享共同的信号通路。然而，与共生发芽相比，真菌对兰科种子的侵染似乎诱导了某些参与脂质和碳水化合物代谢的关键蛋白的更高和更早的表达，从而提高了胚胎中储存物质的利用效率。本研究为兰科种子发芽的分子基础提供了新的见解。