Distinct Endophytic Bacterial Communities Inhabiting Seagrass Seeds.

Flavia Tarquinio,Mathew A Vanderklift,Océane Attlan,Oliver Berry,Andrew Bissett

doi:10.3389/fmicb.2021.703014

Abstract

Seagrasses are marine angiosperms that can live completely or partially submerged in water and perform a variety of significant ecosystem services. Like terrestrial angiosperms, seagrasses can reproduce sexually and, the pollinated female flower develop into fruits and seeds, which represent a critical stage in the life of plants. Seed microbiomes include endophytic microorganisms that in terrestrial plants can affect seed germination and seedling health through phytohormone production, enhanced nutrient availability and defence against pathogens. However, the characteristics and origins of the seagrass seed microbiomes is unknown. Here, we examined the endophytic bacterial community of six microenvironments (flowers, fruits, and seeds, together with leaves, roots, and rhizospheric sediment) of the seagrass Halophila ovalis collected from the Swan Estuary, in southwestern Australia. An amplicon sequencing approach (16S rRNA) was used to characterize the diversity and composition of H. ovalis bacterial microbiomes and identify core microbiome bacteria that were conserved across microenvironments. Distinct communities of bacteria were observed within specific seagrass microenvironments, including the reproductive tissues (flowers, fruits, and seeds). In particular, bacteria previously associated with plant growth promoting characteristics were mainly found within reproductive tissues. Seagrass seed-borne bacteria that exhibit growth promoting traits, the ability to fix nitrogen and anti-pathogenic potential activity, may play a pivotal role in seed survival, as is common for terrestrial plants. We present the endophytic community of the seagrass seeds as foundation for the identification of potential beneficial bacteria and their selection in order to improve seagrass restoration.

Highlights

It is well established that vascular plants form complex interactions and mutualistic relationships with bacteria that play a critical role in supporting plant growth and fitness (Turner et al, 2013; Fitzpatrick et al, 2018)
We investigated the presence of a H. ovalis core microbiome at a population level, within the six H. ovalis microenvironments and followed the changes of core bacteria within the reproductive tissues
The majority of these Operational Taxonomic Units (OTUs) (426 out 710, Figure 1A) belonged to the phylum Proteobacteria which was the dominant lineage within all six microenvironments, representing 87%, 84%, 83%, 83%, 78%, and 63% of the OTUs within seed, fruit, leaf, root, flower, and sediment, respectively (Supplementary Table 2)

Summary

Introduction

It is well established that vascular plants form complex interactions and mutualistic relationships with bacteria that play a critical role in supporting plant growth and fitness (Turner et al, 2013; Fitzpatrick et al, 2018). Seagrasses are marine plants characterised by several ecophysiological traits that allow them to live submerged in water (Les et al, 1997; Hemminga and Duarte, 2000; Kuo and den Hartog, 2006). They are globally distributed throughout the coastlines of all continents (except Antarctica), and are key players in sequestration of carbon dioxide, coastal protection and support of human communities by food provision and tourism (Costanza et al, 1997; Mtwana Nordlund et al, 2016). This is astonishing, given the attention that plant microbiomes have received from the past two decades, and the significant value of seagrasses ($AUD 3.9–5.4 billion for carbon sequestration; Lavery et al, 2013)

Methods

Results

Conclusion