Abstract
Main conclusionWe advanceUlva’s genetic tractability and highlight its value as a model organism by characterizing its APAF1_C/WD40 domain-encoding gene, which belongs to a family that bears homology to R genes.The multicellular chlorophyte alga Ulva mutabilis (Ulvophyceae, Ulvales) is native to coastal ecosystems worldwide and attracts both high socio-economic and scientific interest. To further understand the genetic mechanisms that guide its biology, we present a protocol, based on adapter ligation-mediated PCR, for retrieving flanking sequences in U. mutabilis vector-insertion mutants. In the created insertional library, we identified a null mutant with an insertion in an apoptotic protease activating factor 1 helical domain (APAF1_C)/WD40 repeat domain-encoding gene. Protein domain architecture analysis combined with phylogenetic analysis revealed that this gene is a member of a subfamily that arose early in the evolution of green plants (Viridiplantae) through the acquisition of a gene that also encoded N-terminal nucleotide-binding adaptor shared by APAF-1, certain R-gene products and CED-4 (NB-ARC) and winged helix-like (WH-like) DNA-binding domains. Although phenotypic analysis revealed no mutant phenotype, gene expression levels in control plants correlated to the presence of bacterial symbionts, which U. mutabilis requires for proper morphogenesis. In addition, our analysis led to the discovery of a putative Ulva nucleotide-binding site and leucine-rich repeat (NBS-LRR) Resistance protein (R-protein), and we discuss how the emergence of these R proteins in green plants may be linked to the evolution of the APAF1_C/WD40 protein subfamily.
Highlights
Chlorophyte and streptophyte algae are diverse oxygenic photosynthetic eukaryotes that obtained their chloroplasts through an ancient endosymbiotic event with a cyanobacterium [McFadden 2001; and reviewed in Graham et al (2009); Gawryluk et al 2019]
To establish a method to retrieve vector-insertion flanking sequences from U. mutabilis, we first created a collection of insertional mutants via polyethene glycol-mediated vector transformation
Our research offers a technical advance in the genetic tractability of Ulva mutabilis
Summary
Chlorophyte and streptophyte algae (green algae) are diverse oxygenic photosynthetic eukaryotes that obtained their chloroplasts through an ancient endosymbiotic event with a cyanobacterium [McFadden 2001; and reviewed in Graham et al (2009); Gawryluk et al 2019]. Our understanding of their evolutionary relationships has greatly benefited from recent advances in phylogenomics, which retraced, for example, the trajectory by which land plants evolved from streptophyte algae It is likely that streptophyte algae conquered land multiple times during the course of evolution [reviewed in Delwiche and Cooper (2016) and Fürst-Jansen et al (2020)], while in the chlorophyte lineage, freshwater to marine transitions (or vice versa) frequently occurred (Dittami et al 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
