Abstract

Pro- and eukaryotic microbes associated with multi-cellular organisms are receiving increasing attention as a driving factor in ecosystems. Endophytes in plants can change host performance by altering nutrient uptake, secondary metabolite production or defense mechanisms. Recent studies detected widespread prevalence of Labyrinthula zosterae in European Zostera marina meadows, a protist that allegedly caused a massive amphi-Atlantic seagrass die-off event in the 1930's, while showing only limited virulence today. As a limiting factor for pathogenicity, we investigated genotype×genotype interactions of host and pathogen from different regions (10–100 km-scale) through reciprocal infection. Although the endophyte rapidly infected Z. marina, we found little evidence that Z. marina was negatively impacted by L. zosterae. Instead Z. marina showed enhanced leaf growth and kept endophyte abundance low. Moreover, we found almost no interaction of protist×eelgrass-origin on different parameters of L. zosterae virulence/Z. marina performance, and also no increase in mortality after experimental infection. In a target gene approach, we identified a significant down-regulation in the expression of 6/11 genes from the defense cascade of Z. marina after real-time quantitative PCR, revealing strong immune modulation of the host's defense by a potential parasite for the first time in a marine plant. Nevertheless, one gene involved in phenol synthesis was strongly up-regulated, indicating that Z. marina plants were probably able to control the level of infection. There was no change in expression in a general stress indicator gene (HSP70). Mean L. zosterae abundances decreased below 10% after 16 days of experimental runtime. We conclude that under non-stress conditions L. zosterae infection in the study region is not associated with substantial virulence.

Highlights

  • In the recent past, microorganisms, associated with multicellular organisms, have been receiving increasing attention as a driving factor in ecosystems (e.g. [1])

  • Lesion progression was slightly slower on the 2nd oldest leaf, where only 24% of the leaf surface was black after 3 days

  • Our experiments show that infection with present-day L. zosterae genotypes from North Sea/Baltic Sea in a non- stressful environment is not associated with the detrimental effects on Z. marina described for the wasting disease

Read more

Summary

Introduction

Microorganisms, associated with multicellular organisms, have been receiving increasing attention as a driving factor in ecosystems (e.g. [1]). Endophytes can be parasites and thereby play a crucial role in ecosystems by controlling the dynamics of host populations, by regulating host abundances and, by contributing to ecosystem stability [5]. Whether the host benefits or is degraded by the microbe depends mainly on two factors: the effectiveness of the defense reaction of the host and the pathogenicity of the microorganism. Seagrasses form one of the most valuable coastal ecosystems on earth [9] They are marine flowering plants, which form huge meadows, providing food, shelter and settlement substrate for many organisms. Seagrass meadows contribute to coastal protection [12], play a key role in nutrient cycling [13] and add to water clarity by reducing current velocity and by increasing sedimentation [14]. Since anthropogenic impact on this sensitive ecosystem is still increasing, seagrass populations are declining worldwide [16,17]

Objectives
Methods
Results
Conclusion
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call