Journal Article

Chemical Stimulation of Heterocyte Differentiation by the Feather Moss Hylocomium splendens: a Potential New Step in Plant-Cyanobacteria Symbioses

Elmdam, Isabella Vendel, Timm, Alexander Blinkenberg, Alvarenga, Danillo Oliveira, Rousk, Kathrin

2023

Overview

Cyanobacteria associated with mosses play a key role in the nitrogen (N) cycle in unpolluted ecosystems. Mosses have been found to release molecules that induce morphophysiological changes in epiphytic cyanobionts. Nevertheless, the extent of moss influence on these microorganisms remains unknown. To evaluate how mosses or their metabolites influence N 2 fixation rates by cyanobacteria, we assessed the nitrogenase activity, heterocyte frequency and biomass of a cyanobacterial strain isolated from the feather moss Hylocomium splendens  and a non-symbiotic strain when they were either growing by themselves, together with H. splendens or exposed to H. splendens water, acetone, ethanol, or isopropanol extracts. The same cyanobacterial strains were added to another moss ( Taxiphyllum barbieri ) and a liverwort ( Monosolenium tenerum ) to assess if these bryophytes affect N 2 fixation differently. Although no significant increases in nitrogenase activity by the cyanobacteria were observed when in contact with H. splendens shoots, both the symbiotic and non-symbiotic cyanobacteria increased nitrogenase activity as well as heterocyte frequency significantly upon exposure to H. splendens ethanol extracts. Contact with T. barbieri shoots, on the other hand, did lead to increases in nitrogenase activity, indicating low host-specificity to cyanobacterial activity. These findings suggest that H. splendens produces heterocyte-differentiating factors (HDFs) that are capable of stimulating cyanobacterial N 2 fixation regardless of symbiotic competency. Based on previous knowledge about the chemical ecology and dynamics of moss-cyanobacteria interactions, we speculate that HDF expression by the host takes place in a hypothetical new step occurring after plant colonization and the repression of hormogonia.

• Publisher: Springer US,Springer Nature B.V
• Subject: Acetone / Aquatic plants / biomass / Biomedical and Life Sciences / Bryophyta / Bryophyta - physiology / Bryophytes / Bryopsida - metabolism / Bryopsida - microbiology / Chemical ecology / Colonization / Cyanobacteria / Cyanobacteria - metabolism / Ecology / Ecosystem / epiphytes / Ethanol / Feathers / Fixation / Freshwater plants / Geoecology/Natural Processes / Hormogonia / Host specificity / Hylocomium splendens / isopropyl alcohol / Life Sciences / Metabolites / Microbial Ecology / Microbiology / Microorganisms / Mosses / mosses and liverworts / Nature Conservation / nitrogen / Nitrogen fixation / Nitrogen Fixation - physiology / Nitrogenase / Nitrogenase - metabolism / Nitrogenation / Plant Extracts / Plant Microbe Interactions / Pleurozium schreberi / Shoots / Specificity / Stimulation, Chemical / Symbionts / Symbiosis / Water Quality/Water Pollution