# Action Pathways of Coprinellus radians in Promoting Seed Germination of Cremastra appendiculata

## TL;DR

This study explores how the fungus Coprinellus radians helps the rare orchid Cremastra appendiculata germinate by breaking down seed coats and promoting embryo development.

## Contribution

The study reveals the multi-dimensional action pathways of Coprinellus radians in promoting germination of a rare orchid species.

## Key findings

- C. radians hyphae invade seed coats and promote embryo development within 25 days.
- C. radians secretes enzymes that degrade seed coats and enhance water uptake.
- Transcriptomic analysis shows activation of carbon/energy metabolism genes during symbiosis.

## Abstract

Cremastra appendiculata, a rare medicinal orchid, has extremely low natural seed germination due to immature embryos and dense seed coats, impeding its conservation. Commensal germination with fungi is effective, but the action pathways remain unclear. This study combined morphological observation (scanning electron microscopy and section observation), physiological–biochemical detection (lignocellulolytic enzyme activities, nutrient/hormone contents, FTIR analysis) and transcriptomics to explore Coprinellus radians’ role in C. appendiculata seed germination, with commensal and non-commensal cultures on OMA medium set as experimental and control groups. Results showed C. radians significantly promoted C. appendiculata seed germination and protocorm development (superior to non-commensal conditions). Morphologically, C. radians hyphae invaded seed coats at 6 days post-inoculation; embryos broke through coats and formed apical meristems at 12 days, developing into peloton-containing protocorms at 25 days (breaking dormancy). Physiologically, C. radians secreted lignocellulolytic enzymes (laccase, cellulase, xylanase) to degrade coats, enhancing permeability and water uptake, while driving nutrient accumulation (starch, soluble sugars) and hormone balance. Transcriptomically, symbiosis activated carbon/energy metabolism genes, enriching starch-sucrose metabolism and glycolysis pathways. This study clarifies C. radians’ multi-dimensional action pathways in promoting C. appendiculata germination, providing support for rare orchid conservation.