The Genome of the Fungal Pathogen Verticillium dahliae Reveals Extensive Bacterial to Fungal Gene Transfer
Shi-Kunne, Xiaoqian ; Kooten, Mathijs van; Depotter, Jasper R.L. ; Thomma, Bart P.H.J. ; Seidl, Michael F. - \ 2019
Genome Biology and Evolution 11 (2019)3. - ISSN 1759-6653 - p. 855 - 868.
Verticillium - ascomycete - bacteria - fungus - horizontal gene transfer
Horizontal gene transfer (HGT) involves the transmission of genetic material between distinct evolutionary lineages and can be an important source of biological innovation. Reports of interkingdom HGT to eukaryotic microbial pathogens have accumulated over recent years. Verticillium dahliae is a notorious plant pathogen that causes vascular wilt disease on hundreds of plant species, resulting in high economic losses every year. Previously, the effector gene Ave1 and a glucosyltransferase-encoding gene were identified as virulence factor-encoding genes that were proposed to be horizontally acquired from a plant and a bacterial donor, respectively. However, to what extent HGT contributed to the overall genome composition of V. dahliae remained elusive. Here, we systematically searched for evidence of interkingdom HGT events in the genome of V. dahliae and provide evidence for extensive horizontal gene acquisition from bacterial origin.
Quorum Sensing Controls Adaptive Immunity through the Regulation of Multiple CRISPR-Cas Systems
Patterson, Adrian G. ; Jackson, Simon A. ; Taylor, Corinda ; Evans, Gary B. ; Salmond, George P.C. ; Przybilski, Rita ; Staals, Raymond H.J. ; Fineran, Peter C. - \ 2016
Molecular Cell 64 (2016)6. - ISSN 1097-2765 - p. 1102 - 1108.
bacterial communication - CRISPR-Cas - horizontal gene transfer - phage resistance - quorum sensing - regulation
Bacteria commonly exist in high cell density populations, making them prone to viral predation and horizontal gene transfer (HGT) through transformation and conjugation. To combat these invaders, bacteria possess an arsenal of defenses, such as CRISPR-Cas adaptive immunity. Many bacterial populations coordinate their behavior as cell density increases, using quorum sensing (QS) signaling. In this study, we demonstrate that QS regulation results in increased expression of the type I-E, I-F, and III-A CRISPR-Cas systems in Serratia cells in high-density populations. Strains unable to communicate via QS were less effective at defending against invaders targeted by any of the three CRISPR-Cas systems. Additionally, the acquisition of immunity by the type I-E and I-F systems was impaired in the absence of QS signaling. We propose that bacteria can use chemical communication to modulate the balance between community-level defense requirements in high cell density populations and host fitness costs of basal CRISPR-Cas activity.
Cloning, molecular characterization, and phylogeny of two evolutionary distinct glutamine synthetase isoforms in the green microalga Haematococcus pluvialis (Chlorophyceae)
Reinecke, Diana L. ; Zarka, Aliza ; Leu, Stefan ; Boussiba, Sammy - \ 2016
Journal of Phycology 52 (2016)6. - ISSN 0022-3646 - p. 961 - 972.
alga biotechnology - Archaeplastida - Astaxanthin - Charophyta - glutamine synthetase - green plant evolution - horizontal gene transfer - Lycopodiophyta - nitrogen uptake - transcript regulation
Haematococcus pluvialis (Chlorophyta) is a widely used microalga of great economic potential, yet its molecular genetics and evolution are largely unknown. We present new detailed molecular and phylogenetic analysis of two glutamine synthetase (GS) enzymes and genes (gln) under the Astaxanthin-inducing conditions of light- and nitrogen-stress. Structure analysis identified key residues and confirmed two decameric GS2 holoenzymes, a cytoplasmic enzyme, termed GS2c, and a plastidic form, termed GS2p, due to chloroplast-transit peptides at its N-terminus. Gene expression analysis showed dissociation of mRNA, protein, and enzyme activity levels for both GS2 under different growth conditions, indicating the strong post-transcriptional regulation. Data-mining identified novel and specified published gln genes from Prasinophyceae, Chlorophyta, Trebouxiophyceae, Charophyceae, Bryophyta, Lycopodiophyta, Spermatophyta, and Rhodophyta. Phylogenetic analysis found homologues to the cytosolic GS2c of H. pluvialis in all other photo- and non-photosynthetic Eukaryota. The chloroplastic GS2p was restricted to Chlorophyta, Bryophyta, some Proteobacteria and Fungii; no homologues were identified in Spermatophyta or other Eukaryota. This indicates two independent prokaryotic donors for these two gln genes in H. pluvialis. Combined phylogenetic analysis of GS, chl-b synthase, elongation factor, and light harvesting complex homologues project a newly refined model of Viridiplantae evolution. Herein, a GS1 evolved into the cytosolic GS2c and was passed on to all Eukaryota. Later, the chloroplastic GS2p entered the Archaeplastida lineage via a horizontal gene transfer at the divergence of Chlorophyta and Rhodophyta lineages. GS2p persisted in Chlorophyta and Bryophyta, but was lost during Spermatophyta evolution. These data suggest the revision of GS classification and nomenclature, and extend our understanding of the photosynthetic Eukaryota evolution.