Recent gene duplications dominate evolutionary dynamics of adaptor protein complex subunits in embryophytes.

Adaptor protein complexes and the related complexes COPI and TSET function in packaging vesicles for transport among endomembrane compartments in eukaryotic cells. Differences in the complement of these complexes in lineages such as yeast and mammals as well as apicomplexan and kinetoplastid parasites via loss or duplication of subunits appears to reflect specialization in their respective trafficking systems. The model plant Arabidopsis thaliana possesses multiple paralogues for adaptor protein complex subunits, raising questions as to the timing and extent of these duplications in embryophytes (land plants). However, adaptor protein complex evolution in embryophytes is unexplored. Therefore, we analyzed genomes of diverse embryophytes and closely related green algae using extensive homology searches and phylogenetic analysis of 35 complex subunit proteins. The results reveal numerous paralogues, the vast majority of which, approximately 97%, arose from recent duplication events. This suggests that specialization of these protein complexes may occur frequently but independently in embryophytes.

Small but Mighty: An Update on Small Molecule Plant Cellulose Biosynthesis Inhibitors.

Cellulose is one of the most abundant biopolymers on Earth. It provides mechanical support to growing plant cells and important raw materials for paper, textiles and biofuel feedstocks. Cellulose biosynthesis inhibitors (CBIs) are invaluable tools for studying cellulose biosynthesis and can be important herbicides for controlling weed growth. Here, we review CBIs with particular focus on the most widely used CBIs and recently discovered CBIs. We discuss the effects of these CBIs on plant growth and development and plant cell biology and summarize what is known about the mode of action of these different CBIs.

Long-Read-Based Genome Assembly Reveals Numerous Endogenous Viral Elements in the Green Algal Bacterivore Cymbomonas tetramitiformis.

The marine tetraflagellate Cymbomonas tetramitiformis has drawn attention as an early diverging green alga that uses a phago-mixotrophic mode of nutrition (i.e., the ability to derive nourishment from both photosynthesis and bacterial prey). The Cymbomonas nuclear genome was sequenced previously, but due to the exclusive use of short-read (Illumina) data, the assembly suffered from missing a large proportion of the genome's repeat regions. For this study, we generated Oxford Nanopore long-read and additional short-read Illumina data and performed a hybrid assembly that significantly improved the total assembly size and contiguity. Numerous endogenous viral elements were identified in the repeat regions of the new assembly. These include the complete genome of a giant Algavirales virus along with many genomes of integrated Polinton-like viruses (PLVs) from two groups: Gezel-like PLVs and a novel group of prasinophyte-specific PLVs. The integrated ∼400 kb genome of the giant Algavirales virus is the first account of the association of the uncultured viral family AG_03 with green algae. The complete PLV genomes from C. tetramitiformis ranged between 15 and 25 kb in length and showed a diverse gene content. In addition, heliorhodopsin gene-containing repeat elements of putative mirusvirus origin were identified. These results illustrate past (and possibly ongoing) multiple alga-virus interactions that accompanied the genome evolution of C. tetramitiformis.