[Effects of mycorrhizal planting on small molecular chemical components of Dendrobium officinale].

This study aimed to provide a scientific basis for the application of the mycorrhizal planting technology of Dendrobium officinale by investigating the effects of mycorrhizal planting on the fingerprints of D. officinale and the content of six chemical components. Seventeen samples of D. officinale under mycorrhizal and conventional planting were collected from four regions, such as Jinhua of Zhejiang. The HPLC fingerprints were established to evaluate the similarity of the samples. The content of six chemical components of the samples was determined by HPLC. There were 15 common peaks in the fingerprints, and five of them were identified by marker compounds, which were naringenin, 4,4'-dihydroxy-3,5-dimethoxybibenzyl, 3,4'-dihydroxy-5-methoxybibenzyl, 3',4-dihydroxy-3,5'-dimethoxybibenzyl(gigantol), and 3,4-dihydroxy-4',5-dimethoxybibenzyl(DDB-2). The similarities of the fingerprints of mycorrhizal and conventional planting samples and the control fingerprint were in the ranges of 0.733-0.936 and 0.834-0.942, respectively. The influences of mycorrhizal planting on fingerprints were related to planting regions, the germplasm of D. officianle, and the amount of fungal agent. The content of six chemical components in the samples varied greatly, and the content of DDB-2 was the highest, ranging from 69.83 to 488.47 µg·g~(-1). The mycorrhizal planting samples from Chongming of Shanghai and Taizhou of Jiangsu showed an increase in the content of 5-6 components, while samples from Zhangzhou of Fujian and Jinhua of Zhejiang showed an increase in the content of 1-2 components. The results showed that mycorrhizal planting technology did not change the chemical profile of small molecular chemical components of D. officinale, but affected the content of chemical components such as bibenzyls, which has a good application prospect.

Embryology of Anoectochilus roxburghii: seed and embryo development.

BACKGROUND: Anoectochilus roxburghii is known for its medicinal properties, culinary interests, and ornamental applications in Asian countries. Recent studies focus mainly on its phytochemical properties and little is known about its reproductive biology, especially seed and embryo development. This study documents the major developmental events in seed and embryo development of A. roxburghii upon pollination. RESULTS: Morphological and histological studies revealed that upon pollination embryo and seed development is completed in 40 days. Ovular primordia are at the megaspore mother cell stage at the time of anthesis. Embryo development proceeds after a successful fertilization. A. roxburghii has a single cell suspensor. It elongates but not extended beyond the seed coat. A distinct cell gradient is present within the embryo proper with smaller cells located towards the chalazal end of the seed. Proteins and lipids are the major storage products within the embryo proper cells. At the stage of early globular embryo, the inner seed coat has degenerated and thus a carapace is absent at maturity. A limited deposition of lignin is detected in the mature seed coat. CONCLUSIONS: The seed of A. roxburghii matures rapidly. At maturity, the embryo proper has a well-differentiated apical zone with little constraints impose by the seed coat. These characters indicate adaptations to fast germination that may ensure a successful colonization in the shaded forest understory.

Comparative Transcriptome Analysis of Genes Involved in GA-GID1-DELLA Regulatory Module in Symbiotic and Asymbiotic Seed Germination of Anoectochilus roxburghii (Wall.) Lindl. (Orchidaceae).

Anoectochilus roxburghii (Wall.) Lindl. (Orchidaceae) is an endangered medicinal plant in China, also called "King Medicine". Due to lacking of sufficient nutrients in dust-like seeds, orchid species depend on mycorrhizal fungi for seed germination in the wild. As part of a conservation plan for the species, research on seed germination is necessary. However, the molecular mechanism of seed germination and underlying orchid-fungus interactions during symbiotic germination are poorly understood. In this study, Illumina HiSeq 4000 transcriptome sequencing was performed to generate a substantial sequence dataset of germinating A. roxburghii seed. A mean of 44,214,845 clean reads were obtained from each sample. 173,781 unigenes with a mean length of 653 nt were obtained. A total of 51,514 (29.64%) sequences were annotated, among these, 49 unigenes encoding proteins involved in GA-GID1-DELLA regulatory module, including 31 unigenes involved in GA metabolism pathway, 5 unigenes encoding GID1, 11 unigenes for DELLA and 2 unigenes for GID2. A total of 11,881 genes showed significant differential expression in the symbiotic germinating seed sample compared with the asymbiotic germinating seed sample, of which six were involved in the GA-GID1-DELLA regulatory module, and suggested that they might be induced or suppressed by fungi. These results will help us understand better the molecular mechanism of orchid seed germination and orchid-fungus symbiosis.

The promoting role of an isolate of dark-septate fungus on its host plant Saussurea involucrata Kar. et Kir.

A dark-septate endophytic (DSE) fungus EF-37 was isolated from the roots of Saussurea involucrata Kar. et Kir., an endangered Chinese medicinal plant. The molecular identification of the fungus was based on internal transcribed spacer regions and the result showed that EF-37 was congeneric to Mycocentrospora. This study was conducted to clarify the influence of the root endophyte EF-37 on the host plant S. involucrata using material grown in a sterile culture bottle. After cultivation for 40 days, fungal hyphae were found to be branching repeatedly and forming "hyphae nets" in the epidermal layers. Significant differences were detected between the study groups in plant dry weight, plant height, root dry weight, shoot dry weight, and the number of hair root tips. There was a positive effect of endophyte EF-37 on plant root development, with results showing that cortical cells dissolved and formed aerate structures. There was a positive effect of endophyte EF-37 on plant growth, but chlorophyll fluorescence analysis showed that there were no significant differences between the study groups. In addition, analysis of the chemical composition of seedlings showed that the level of rutin was higher in plants cultivated with the EF-37 fungus compared to the controls. This study helps to establish a basis for germplasm conservation and for further investigation of the interaction between dark-septate fungi and this alpine plant.