New Insights into the Symbiotic Relationship between Orchids and Fungi

Chuan-Ming Yeh,Kwimi Chung,Chieh-Kai Liang,Wen-Chieh Tsai

doi:10.3390/app9030585

Abstract

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.

Highlights

All living organisms essentially interact and communicate with their surrounding organisms for their survival
Orchid seeds cannot germinate in the absence of symbiosis with mycorrhizal fungi
It has been long believed that orchids receive mineral nutrients, such as

Summary

Introduction

All living organisms essentially interact and communicate with their surrounding organisms for their survival. One of the well-known benefits of mycorrhizas to both plants and fungi is nutrient acquisition. Mycorrhizas are commonly classified into the following groups based on the anatomical aspects, such as the presence of internal hyphae of mycorrhizal fungi in the host plant cells: (1) Ectomycorrhiza: about 5,000 species of fungi do not enter the cells, but create a mycelial. 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]. 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

Orchid Mycorrhiza and Its Role in Orchid Seed Germination

Nutrient Exchange between Orchids and Mycorrhizal Fungi

Findings

Conclusions and Future Perspectives