Diversity of Frankia Strains, Actinobacterial Symbionts of Actinorhizal Plants

Abstract

In the last edition of the Bergey's Manual of Systematic Bacteriology, Frankia was the sole genus found in the family Frankiaceae. This single-genus family, together with Geodermatophilaceae, Nakamurellaceae, Sporichthyaceae, Acidothermaceae, and Cryptosporangiaceae, makes up the order Frankiales, an artificial taxon within the phylum Actinobacteria supported only marginally by 16S rDNA similarities (Normand and Benson 2012). Genus Frankia represents a monophyletic assemblage of soil actinobacteria distinguishable by multilocular sporangia-forming branched hyphae and their unique ability to grow in nitrogen-limited substrates due to their ability to fix nitrogen within specialized thick-walled structures, termed vesicles, produced in vitro and in planta. Diversity of Frankia has been noted in several separate reports on the presence of comparable root nodule structures induced in numerous trees and shrubs growing as aggressive pioneers in nitrogenlimited ecosystems such as glacial moraines, gravel slopes, volcanic ashes, mine spoils, or burned forests with a contributed input of 15 % of total biologically fixed nitrogen on earth (Quispel 1990). Despite the absence of apparent close kinship among these plants, they have been termed actinorhizal plants due to the nature of the root nodule-causing agents detected in plant tissues. Based on in planta morphology and the limited cross-infectivity of crushed-nodule inocula, Becking

Browsing impacts on the stable isotope composition of chaparral plants

“…Recent molecular—and particularly genomic—studies show at least 19 “genospecies” (variously strains, groups, or clusters) that may be related to host plants or free‐living life styles (Normand and Fernandez , Gtari et al. ). Frankia living in host plants with narrow geographical ranges, including Ceanothus, have small genomes and low genetic diversity (Gtari et al.…”

“…Frankia living in host plants with narrow geographical ranges, including Ceanothus, have small genomes and low genetic diversity (Gtari et al. ), with possible local differentiation across host species (Oakley et al. ).…”

Physiological effects of major up-regulated Alnus glutinosa peptides on Frankia sp. ACN14a

“…New '-omics' technologies are improving our understanding of host-bacteria relationships, in particular the Alnus-Frankia symbiosis. Genome descriptions Gtari et al, 2014), transcriptomics (Alloisio et al, 2010) and proteomics (Hammad et al, 2001;Alloisio et al, 2007) have yielded many potential symbiotic determinants in recent years that are being studied by various complementary biochemical and genetic approaches to assess their role in symbiosis.…”

19th International Meeting on Frankia and Actinorhizal Plants

“…Since 2016, the availability of many Frankia genomes ) covering the major Frankia clades (Gtari et al 2013), and the incorporation of comparative genome data, omniLog phenoarrays, morphology, chemotaxonomy and host plant range knowledge have enabled species definitions according to conventional nomenclature. Gtari et al (2019) summarise current Frankia taxonomy and provide keys features of the 11 species with validly published names that have been proposed within the genus Frankia.…”

“…While the overall clustering of the four Frankia lineages remains conserved between each locus analysed with different levels of resolution (Gtari et al 2013), the precise evolutionary history of the four clusters remains unclear and inconsistent. This topology is has been explored using a variety of approaches.…”