Nitrogen transport in the orchid mycorrhizal symbiosis – further evidence for a mutualistic association

Dearnaley, J. D. W.; Cameron, Duncan D.

doi:10.1111/nph.14357

Cited by 61 publications

(56 citation statements)

References 18 publications

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“…In addition, TcGS1 and TcGOGAT, the fungal genes encoding glutamine synthetase and glutamate synthase in the N assimilation pathway, are also up-regulated in mycorrhizal protocorms. A commentary of this study by Dearnaley and Cameron (2017) concluded that the fungus, T. calospora, may receive ammonium from its orchid host, S. vomeracea, during seed germination and protocorm development. Therefore, a true mutualism may be also present in the initially mycoheterotrophic stage of autotrophic orchids or myco-heterotrophic orchids [29].…”

Section: Nutrient Exchange Between Orchids and Mycorrhizal Fungimentioning

confidence: 93%

“…However, recent evidence suggests that not only carbohydrates but also lipids can be transferred from host plants to fungi as C resources [27,28]. The mechanisms of how ectomycorrhizal and arbuscular mycorrhizal fungi take up and transfer mineral nutrients to their host plants for exchanging C resources are extensively studied; however, much less attention has been paid to ericoid and orchid mycorrhizal fungi [3,23,29]. Several detailed reviews on the mutualistic interactions between plants and fungi that form ectomycorrhizal or arbuscular mycorrhizal symbiosis have been published [3,[23][24][25][26]30].…”

Section: Nutrient Exchange Between Orchids and Mycorrhizal Fungimentioning

confidence: 99%

“…Compared to the other types of mycorrhizas, the orchid-fungus symbiosis is considered to be unique since the nutrient movement is not bi-directional in the early developmental stages and even in adults of some orchid species [29]. As the orchid seeds are very tiny with very little storage, colonization by fungi is required for their germination and/or early protocorm development [15].…”

Section: Nutrient Exchange Between Orchids and Mycorrhizal Fungimentioning

confidence: 99%

“…As the orchid seeds are very tiny with very little storage, colonization by fungi is required for their germination and/or early protocorm development [15]. Therefore, the mycorrhizal fungi were thought to provide both mineral nutrients and C to the non-photosynthetic orchid seedlings and to receive no reward [29]. However, similar to all other mycorrhizal symbioses, the mycorrhizal fungi receive C as a reward for exchanging mineral nutrients after orchids develop green leaves for photosynthesis [31].…”

Section: Nutrient Exchange Between Orchids and Mycorrhizal Fungimentioning

confidence: 99%

“…The well-known non-mutualistic interaction between non-photosynthetic orchids and their symbiotic fungi was challenged by a recent study using mycorrhizas formed between Serapias vomeracea (orchid) and Tulasnella calospora (fungus) to investigate expression of orchid and fungal N transport and assimilation genes [29,37]. It was demonstrated that the fungal low-affinity ammonium transporter gene, TcAMT2, is significantly upregulated in symbiosis and the transcripts corresponding to TcAMT2 are detected in the orchid protocorm cells containing fungal pelotons by laser microdissection analysis.…”

Section: Nutrient Exchange Between Orchids and Mycorrhizal Fungimentioning

confidence: 99%

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New Insights into the Symbiotic Relationship between Orchids and Fungi

Yeh¹,

Chung

Liang

et al. 2019

Applied Sciences

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Mycorrhizas play an important role in plant growth and development. In mycorrhizal symbioses, fungi supply soil mineral nutrients, such as nitrogen and phosphorus, to their host plants in exchange for carbon resources. Plants gain as much as 80% of mineral nutrient requirements from mycorrhizal fungi, which form associations with the roots of over 90% of all plant species. Orchid seeds lack endosperms and contain very limited storage reserves. Therefore, the symbiosis with mycorrhizal fungi that form endomycorrhizas is essential for orchid seed germination and protocorm development under natural conditions. The rapid advancement of next-generation sequencing contributes to identifying the orchid and fungal genes involved in the orchid mycorrhizal symbiosis and unraveling the molecular mechanisms regulating the symbiosis. We aim to update and summarize the current understanding of the mechanisms on orchid-fungus symbiosis, and the main focus will be on the nutrient exchange between orchids and their fungal partners. Appl. Sci. 2019, 9, 585 2 of 14 sheath, which functions as a plant-fungus interface, surrounding the epidermal and outer cortical cells. The interface is used for the bidirectional nutrient transfer between a plant and its fungal partner [7]. (2) Endomycorrhiza: the fungi possess specific types of hyphae such as arbuscules and coils to penetrate and grow inside of the root cells of host plants [3]. Endomycorrhizas can be further classified as ectendomycorrhizas, ericoid, arbutoid, monotropoid, orchid and arbuscular mycorrhizas based on the specificity of plant families and the type of internal hyphae [3,8]. Ectomycorrhizas are also alternatively represented as arbuscular mycorrhizas because the class is the most prevalent type of mycorrhizae, as shown in approximately 71% of all vascular plant species [1,9].The Orchidaceae is the largest family of flowering plants including over 700 genera and about 30,000-35,000 species and still hundreds of new species displaying variable floral features, lifestyles, habitat distributions and trophic patterns are being discovered and developed every year [10,11]. Mycorrhizas in orchid species are highly important throughout their whole life including germination and further development. In this article, we provide a brief review of the roles of mycorrhizas in orchid growth and development and the current understanding of the mechanisms in nutrient exchange between orchids and their fungal partners.

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Section: Nutrient Exchange Between Orchids and Mycorrhizal Fungimentioning

confidence: 93%