Gastrodia elata is a well-known medicinal orchid. In nature, the germination rate of G. elata is extremely poor, because there is no endosperm within the mature seed. It is crucial for G. elata to obtain nutrition from mycorrhizal fungi (Mycena) at the early-stage of germination. After germination, the seed gives rise to a protocorm. However, there are no “omic” studies on understanding the interaction between Gastrodia and Mycena. Here, we used transcriptomic approaches to explore changes in seed germination of G. elata. Based on RNA-Seq, a total of ~221 million clean reads were assembled denovo into 139,756 unigenes, including 42,140 unigenes that were annotated in public databases. Meanwhile, 1750 unigenes were identified as differentially expressed genes. Most of these differentially expressed genes were putatively involved in energy metabolism, plant defense, molecular signaling, and secondary metabolism. Additionally, numerous genes involved in clathrin-mediated endocytosis were identified from our data. Most of these genes (e.g., clathrin, adaptor protein, dynamin, HSC70) were basally expressed in seeds and highly expressed in protocorms. Our data suggested that clathrin-mediated endocytosis could play important roles in symbiotic seed germination of G. elata with Mycena infections.

Gastrodia elata, a mycoheterotrophic orchid, is a well-known medicinal herb. In nature, the seed germination of G. elata requires proper fungal association, because of the absence of endosperm. To germinate successfully, G. elata obtains nutrition from mycorrhizal fungi such as Mycena. However, Mycena is not able to supply nutrition for the further development and enlargement of protocorms into tubers, flowering and fruit setting of G. elata. To date, current genomic studies on this topic are limited. Here we used the proteomic approach to explore changes in G. elata at different stages of symbiotic germination. Using mass spectrometry, 3787 unique proteins were identified, of which 599 were classified as differentially accumulated proteins. Most of these differentially accumulated proteins were putatively involved in energy metabolism, plant defense, molecular signaling, and secondary metabolism. Among them, the defense genes (e.g., pathogenesis-/wound-related proteins, peroxidases, and serine/threonine-protein kinase) were highly expressed in late-stage protocorms, suggesting that fungal colonization triggered the significant defense responses of G. elata. The present study indicated the metabolic change and defensive reaction could disrupt the balance between Mycena and G. elata during mycorrhizal symbiotic germination.