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Xu ZX, Zhu XM, Yin H, Li B, Chen XJ, Fan XL, Li NQ, Selosse MA, Gao JY, Han JJ. Symbiosis between Dendrobium catenatum protocorms and Serendipita indica involves the plant hypoxia response pathway. PLANT PHYSIOLOGY 2023; 192:2554-2568. [PMID: 36988071 PMCID: PMC10315314 DOI: 10.1093/plphys/kiad198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/07/2023] [Accepted: 03/08/2023] [Indexed: 06/19/2023]
Abstract
Mycorrhizae are ubiquitous symbioses established between fungi and plant roots. Orchids, in particular, require compatible mycorrhizal fungi for seed germination and protocorm development. Unlike arbuscular mycorrhizal fungi, which have wide host ranges, orchid mycorrhizal fungi are often highly specific to their host orchids. However, the molecular mechanism of orchid mycorrhizal symbiosis is largely unknown compared to that of arbuscular mycorrhizal and rhizobial symbiosis. Here, we report that an endophytic Sebacinales fungus, Serendipita indica, promotes seed germination and the development of protocorms into plantlets in several epiphytic Epidendroideae orchid species (6 species in 2 genera), including Dendrobium catenatum, a critically endangered orchid with high medicinal value. Although plant-pathogen interaction and high meristematic activity can induce the hypoxic response in plants, it has been unclear whether interactions with beneficial fungi, especially mycorrhizal ones, also involve the hypoxic response. By studying the symbiotic relationship between D. catenatum and S. indica, we determined that hypoxia-responsive genes, such as those encoding alcohol dehydrogenase (ADH), are highly induced in symbiotic D. catenatum protocorms. In situ hybridization assay indicated that the ADH gene is predominantly expressed in the basal mycorrhizal region of symbiotic protocorms. Additionally, the ADH inhibitors puerarin and 4-methylpyrazole both decreased S. indica colonization in D. catenatum protocorms. Thus, our study reveals that S. indica is widely compatible with orchids and that ADH and its related hypoxia-responsive pathway are involved in establishing successful symbiotic relationships in germinating orchids.
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Affiliation(s)
- Zhi-Xiong Xu
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650500, China
| | - Xin-Meng Zhu
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650500, China
| | - Huachun Yin
- College of Life Sciences, Chongqing Normal University, Chongqing 401331, China
| | - Bo Li
- College of Life Sciences, Chongqing Normal University, Chongqing 401331, China
| | - Xiao-Jie Chen
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650500, China
| | - Xu-Li Fan
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650500, China
| | - Neng-Qi Li
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650500, China
| | - Marc-André Selosse
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Institut de Systématique, Évolution, Biodiversité (UMR 7205-CNRS, MNHN, UPMC, EPHE), Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, 75005 Paris, France
- University of Gdańsk, Faculty of Biology, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland
- Institut Universitaire de France (IUF), Paris, France
| | - Jiang-Yun Gao
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650500, China
| | - Jia-Jia Han
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
- Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650500, China
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Symbiotic Culture of Three Closely Related Dendrobium Species Reveals a Growth Bottleneck and Differences in Mycorrhizal Specificity at Early Developmental Stages. DIVERSITY 2022. [DOI: 10.3390/d14121119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Mycorrhizal specificity, i.e., the range of fungi allowing mycorrhizal partnerships, differs among orchid species, but that at early developmental stages is unclear. We investigated whether mycorrhizal specificity during seed germination and seedling development differs among three Dendrobium species, D. officinale, D. okinawense and D. moniliforme, in vitro. Nine mycorrhizal fungal strains were obtained from the roots of these species and cultured with a seed of each Dendrobium species. Five to eight fungal strains stimulated seed germination, whereas one to four fungal isolates significantly promoted protocorm development in the three species. To evaluate effects on leafy seedling growth, seedlings obtained from asymbiotic culture were cultured with nine fungal isolates. D. officinale and D. okinawense showed specificity for a single Serendipitaceae or Tulasnellaceae isolate, whereas D. moniliforme exhibited specificity for three isolates of Serendipitaceae and Tulasnellaceae. Therefore, the three Dendrobium species had a growth bottleneck from seed germination to the protocorm stage, and mycorrhizal specificity of protocorm growth and seedling development in vitro varied among the species. Our findings imply divergent mycorrhizal specificity in Dendrobium species at early developmental stages. This study provides insights into the diversity of orchid mycorrhizal specificity, as well as valuable information for conservation of endangered orchids.
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Zhang L, Rammitsu K, Tetsuka K, Yukawa T, Ogura-Tsujita Y. Dominant Dendrobium officinale mycorrhizal partners vary among habitats and strongly induce seed germination in vitro. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.994641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dendrobium officinale (Orchidaceae) is an endangered epiphytic orchid that has been well studied as a medicinal plant. Although previous studies have shown that various fungal isolates promote D. officinale seed germination and seedling development in vitro, mycorrhizal associations among its wild populations remain poorly understood. In this study, we identified mycorrhizal fungi associated with D. officinale (36 individuals from six sites) using Sanger sequencing and compared fungal communities among sites and habitats (lithophytic vs. epiphytic individuals). Among the obtained sequences, 76 belonged to orchid mycorrhizal fungi (OMF), among which Tulasnellaceae accounted for 45.8% and Serendipitaceae for 28.1%. The Serendipitaceae operational taxonomic unit (OTU) SE1 was the most dominant partner, accounting for 27.1% of all detected fungal sequences, followed by a Tulasnellaceae OTU, TU27, which accounted for 15.6%. The relative frequencies of Serendipitaceae and Tulasnellaceae differed greatly between lithophytic and epiphytic individuals. Serendipitaceae accounted for 47.3% of the OMF sequences among lithophytes, and Tulasnellaceae for 95.2% among epiphytes. Mycorrhizal community composition also varied among sites. We further conducted in vitro symbiotic culture from seeds with six fungal isolates. Two Serendipitaceae and two Tulasnellaceae isolates, including SE1 and TU27, significantly promoted seed germination and seedling development. These results indicate that D. officinale is mainly associated with Tulasnellaceae and Serendipitaceae as its main fungal partners, which strongly induced seed germination and seedling development in vitro, suggesting their association with D. officinale through its life cycle.
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Yao N, Wang T, Cao X. Epidendrumradicans Fungal Community during Ex Situ Germination and Isolation of Germination-Enhancing Fungi. Microorganisms 2022; 10:microorganisms10091841. [PMID: 36144443 PMCID: PMC9503211 DOI: 10.3390/microorganisms10091841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 08/09/2022] [Accepted: 08/30/2022] [Indexed: 11/19/2022] Open
Abstract
Orchids exhibit varying specificities to fungi in different microbial environments. This pilot study investigated the preference of fungal recruitment during symbiotic germination of Epidendrum radicans Pav. ex Lindl. Two different orchid substrates were used for ex situ seed baiting: pine bark and rotten oak leaf, with Basidiomycota and Ascomycota as the respective dominant groups. Both substrates promoted seed germination, with a higher protocorm formation rate on pine bark (65.75%). High-throughput sequencing characterized the fungal communities of germinated protocorms. Basidiomycota was the dominant group in protocorms that symbiotically germinated on both substrates. The family-level community structures of endophytic fungi in protocorms that symbiotically germinated on both substrates were close to those of protocorms that germinated in vitro on MS1 medium. For protocorms, the dominant fungal groups recruited from substrates differed at the genus level; from pine bark, they were genera belonging to unclassified Sebacinales (41.34%), Thanatephorus (14.48%) and Fusarium (7.35%), while, from rotten oak leaf, they were Rhizoctonia (49.46%), Clitopilus (34.61%), and Oliveonia (7.96%). Four fungal isolates were successfully obtained and identified as belonging to the family Tulasnellaceae, genera Ceratobasidium and Peniophora, which could promote seed germination to the seedling stage. The data indicate that endophytic fungi for E. radicans germination on two different substrates are affected at the genus level by the substrate, with a degree of specificity at the family level.
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Affiliation(s)
- Na Yao
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China
| | - Tao Wang
- Beijing Laboratory of Urban and Rural Ecological Environment, Beijing Floriculture Engineering Technology Research Centre, China National Botanical Garden, Beijing 100093, China
| | - Xiaolu Cao
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China
- Correspondence:
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Ma GH, Chen XG, Selosse MA, Gao JY. Compatible and Incompatible Mycorrhizal Fungi With Seeds of Dendrobium Species: The Colonization Process and Effects of Coculture on Germination and Seedling Development. FRONTIERS IN PLANT SCIENCE 2022; 13:823794. [PMID: 35360307 PMCID: PMC8961024 DOI: 10.3389/fpls.2022.823794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 01/28/2022] [Indexed: 05/14/2023]
Abstract
Orchids highly rely on mycorrhizal fungi for seed germination, and compatible fungi could effectively promote germination up to seedlings, while incompatible fungi may stimulate germination but do not support subsequent seedling development. In this study, we compared the fungal colonization process among two compatible and two incompatible fungi during seed germination of Dendrobium officinale. The two compatible fungi, i.e., Tulasnella SSCDO-5 and Sebacinales LQ, originally from different habitats, could persistently colonize seeds and form a large number of pelotons continuously in the basal cells, and both fungi promoted seed germination up to seedling with relative effectiveness. In contrast, the two incompatible fungi, i.e., Tulasnella FDd1 and Tulasnella AgP-1, could not persistently colonize seeds. No pelotons in the FDd1 treatment and only a few pelotons in the AgP-1 treatment were observed; moreover, no seedlings were developed at 120 days after incubation in either incompatible fungal treatment. The pattern of fungal hyphae colonizing seeds was well-matched with the morphological differentiation of seed germination and seedling development. In the fungal cocultural experiments, for both orchids of D. officinale and Dendrobium devonianum, cocultures had slightly negative effects on seed germination, protocorm formation, and seedling formation compared with the monocultures with compatible fungus. These results provide us with a better understanding of orchid mycorrhizal interactions; therefore, for orchid conservation based on symbiotic seed germination, it is recommended that a single, compatible, and ecological/habitat-specific fungus can be utilized for seed germination.
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Affiliation(s)
- Guang-Hui Ma
- School of Ecology and Environmental Science, Yunnan University, Kunming, China
- Institute of International Rivers and Eco-Security, Yunnan University, Kunming, China
| | - Xiang-Gui Chen
- School of Ecology and Environmental Science, Yunnan University, Kunming, China
| | - Marc-André Selosse
- School of Ecology and Environmental Science, Yunnan University, Kunming, China
- Institut de Systématique, Évolution, Biodiversité, Muséum National d’Histoire Naturelle, Sorbonne Universités, Paris, France
| | - Jiang-Yun Gao
- School of Ecology and Environmental Science, Yunnan University, Kunming, China
- *Correspondence: Jiang-Yun Gao,
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