Endogenous viral elements in algal genomes

Endogenous viral elements （EVEs） are host-genomic fragments originated from viral genomes. They have been found universally in animal and plant genomes. Here we carried out a systematic screening and analy-sis of EVEs in algal genomes and found that EVEs commonly exist in algal genomes. We classified the EVE fragments into three categories according to the length of EVE fragments. Due to the probability of sequence similarity by chance, we ignored the potential function of medium-length EVE fragments. However, long-length EVE fragments probably had capability to encode protein domains or even entire proteins, and some short-length EVE fragments had high similarity with host＇s siRNA sequences and possibly served functions of small RNAs. Therefore, short and long EVE fragments might provide regulomic and proteomic novelty to the host＇s metabolism and adaptation. We also found several EVE fragments shared by more than 3 algal genomes. By phylogenetic analysis of the shared EVEs and their corresponding species, we found that the integration of viral fragments into host genomes was an ancient event, possibly before the divergence of Chlorophytes and Ochrophytes. Our findings show that there is a frequent genetic flow from viruses to algal genomes. Moreover, study on algal EVEs shed light on the virus-host interaction in large timescale and could also help us understand the balance of marine ecosystems.

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.

A single-cell atlas of mouse olfactory bulb chromatin accessibility

Olfaction,the sense of smell,is a fundamental trait crucial to many species.The olfactory bulb(OB)plays pivotal roles in processing and transmitting odor information from the environment to the brain.The cellular heterogeneity of the mouse OB has been studied using single-cell RNA sequencing.However,the epigenetic landscape of the m OB remains mostly unexplored.Herein,we apply single-cell assay for transposaseaccessible chromatin sequencing to profile the genome-wide chromatin accessibility of 9,549 single cells from the m OB.Based on single-cell epigenetic signatures,m OB cells are classified into 21 clusters corresponding to 11 cell types.We identify distinct sets of putative regulatory elements specific to each cell cluster from which putative target genes and enriched potential functions are inferred.In addition,the transcription factor motifs enriched in each cell cluster are determined to indicate the developmental fate of each cell lineage.Our study provides a valuable epigenetic data set for the m OB at single-cell resolution,and the results can enhance our understanding of regulatory circuits and the therapeutic capacity of the OB at the single-cell level.