Role of an FNIP Repeat Domain-Containing Protein Encoded by Megavirus Baoshan during Viral Infection

Megavirus baoshanense Mb0671 modulates host translation and increases viral fitness

Amoeba giant viruses encode many translation-related proteins, but the function of these proteins remains obscure. In the current work, we studied the potential eukaryotic translation initiation factor 4A (eIF4A, Mb0671) encoded by Megavirus baoshanense, a member of the family Mimiviridae. The protein was shown to possesse ATPase activity and RNA-binding capacity, localize in the cytoplasm of infected cells, and present in mature virions. Interactome analysis showed that Mb0671 interacted primarily with ribosomal proteins and translation-related proteins. Specifically, Mb0671 was found to interact indirectly with host eIF4A, suggesting that it was associated with the translation apparatus. Proteomic analysis revealed that the protein profile of Acanthamoeba castellanii cells stably expressing Mb0671 was altered significantly compared to wild-type cells. The cellular proteins that were significantly upregulated included those in the pathways of spliceosome, amino acids biosynthesis, ribosome biogenesis, vesicular transportation, mTOR signaling pathway, etc. Both Mb0671 overexpression or siRNA-mediated reduction of its expression level significantly affected the synthesis of viral proteins. Furthermore, overexpressing Mb0671 accelerated cell growth and virus replication, whereas reduction of Mb0671 expression by siRNA delayed virus replication. These results suggested that Mb0671 altered cellular translation, possibly through its association with the host translation machinery, and played an important role in enhancing virus adaptability.

Conserved marseilleviruses harboring diverse antibiotic resistance genes isolated from the Yangtze river Delta and the Pearl river delta, China

Marseilleviruses are a group of double-stranded DNA viruses infecting Acanthamoeba within the phylum Nucleocytoviricota and are ubiquitous in water and soil globally. Here, we report six strains of marseilleviruses isolated from environmental samples in the Yangtze River Delta and the Pearl River Delta, China. Viral particles exhibited icosahedral shaped capsids measuring about 220 ~ 240 nm in diameter. Based on stability assays, viral particles were halotolerant and acid-tolerant, but sensitive to chloroform and high temperature. Genomics and phylogenetic analyses showed that these strains were highly conserved compared with other reported marseilleviruses. Diverse members of the small multidrug resistance (SMR) family of transporter, which is a type of antibiotics resistance gene (ARG) and contribute to the feature of antibiotic resistance in bacteria, to our best knowledge, are firstly described in Marseilleviridae. The alignments of primary structures and in-silico tertiary structures reveal structural and potential functional similarity between giant viral and bacterial SMR, suggesting a possible role in viruses' interaction with antibiotics. The biological properties of marseillevirus and the discovery of viral SMR provide insight in the external and intracellular environment fitness of these large amoeba-infecting viruses.

Macroalgal deep genomics illuminate multiple paths to aquatic, photosynthetic multicellularity

Macroalgae are multicellular, aquatic autotrophs that play vital roles in global climate maintenance and have diverse applications in biotechnology and eco-engineering, which are directly linked to their multicellularity phenotypes. However, their genomic diversity and the evolutionary mechanisms underlying multicellularity in these organisms remain uncharacterized. In this study, we sequenced 110 macroalgal genomes from diverse climates and phyla, and identified key genomic features that distinguish them from their microalgal relatives. Genes for cell adhesion, extracellular matrix formation, cell polarity, transport, and cell differentiation distinguish macroalgae from microalgae across all three major phyla, constituting conserved and unique gene sets supporting multicellular processes. Adhesome genes show phylum- and climate-specific expansions that may facilitate niche adaptation. Collectively, our study reveals genetic determinants of convergent and divergent evolutionary trajectories that have shaped morphological diversity in macroalgae and provides genome-wide frameworks to understand photosynthetic multicellular evolution in aquatic environments.

Crystal structures of FNIP/FGxxFN motif-containing leucine-rich repeat proteins

The Cafeteria roenbergensis virus (Crov), Dictyostelium, and other species encode a large family of leucine-rich repeat (LRR) proteins with FGxxFN motifs. We determined the structures of two of them and observed several unique structural features that set them aside from previously characterized LRR family members. Crov588 comprises 25 regular repeats with a LxxLxFGxxFNQxIxENVLPxx consensus, forming a unique closed circular repeat structure. Novel features include a repositioning of a conserved asparagine at the middle of the repeat, a double phenylalanine spine that generates an alternate core packing arrangement, and a histidine/tyrosine ladder on the concave surface. Crov539 is smaller, comprising 12 repeats of a similar LxxLxFGxxFNQPIExVxW/LPxx consensus and forming an unusual cap-swapped dimer structure. The phenylalanine spine of Crov539 is supplemented with a tryptophan spine, while a hydrophobic isoleucine-rich patch is found on the central concave surface. We present a detailed analysis of the structures of Crov588 and Crov539 and compare them to related repeat proteins and other LRR classes.