Amborella trichopoda is strongly supported as the single living species of the sister lineage to all other extant flowering plants, providing a unique reference for inferring the genome content and structure of the most recent common ancestor (MRCA) of living angiosperms. Sequencing the Amborella genome, we identified an ancient genome duplication predating angiosperm diversification, without evidence of subsequent, lineage-specific genome duplications. Comparisons between Amborella and other angiosperms facilitated reconstruction of the ancestral angiosperm gene content and gene order in the MRCA of core eudicots. We identify new gene families, gene duplications, and floral protein-protein interactions that first appeared in the ancestral angiosperm. Transposable elements in Amborella are ancient and highly divergent, with no recent transposon radiations. Population genomic analysis across Amborella's native range in New Caledonia reveals a recent genetic bottleneck and geographic structure with conservation implications.

The maize W22 inbred has served as a platform for maize genetics since the mid twentieth century. To streamline maize genome analyses, we have sequenced and de novo assembled a W22 reference genome using short-read sequencing technologies. We show that significant structural heterogeneity exists in comparison to the B73 reference genome at multiple scales, from transposon composition and copy number variation to single-nucleotide polymorphisms. The generation of this reference genome enables accurate placement of thousands of Mutator (Mu) and Dissociation (Ds) transposable element insertions for reverse and forward genetics studies. Annotation of the genome has been achieved using RNA-seq analysis, differential nuclease sensitivity profiling and bisulfite sequencing to map open reading frames, open chromatin sites and DNA methylation profiles, respectively. Collectively, the resources developed here integrate W22 as a community reference genome for functional genomics and provide a foundation for the maize pan-genome.

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Molecular phylogenies are useful for answering deep questions in conifer evolution if they depend on understanding relationships among extant lineages. Because of extinction, however, molecular datasets poorly sample diversity from periods much earlier than the Late Cretaceous. This fundamentally limits their utility for understanding deep patterns of character evolution and resolving the overall pattern of conifer phylogeny.

Alternative splicing (AS) is a major source of transcript and proteome diversity, but examining AS in species without well-annotated reference genomes remains difficult. Research on both human and mouse has demonstrated the advantages of using Iso-Seq™ data for isoform-level transcriptome analysis, including the study of AS and gene fusion. We applied Iso-Seq™ to investigate AS in Amborella trichopoda, a phylogenetically pivotal species that is sister to all other living angiosperms. Our data show that, compared with RNA-Seq data, the Iso-Seq™ platform provides better recovery on large transcripts, new gene locus identification and gene model correction. Reference-based AS detection with Iso-Seq™ data identifies AS within a higher fraction of multi-exonic genes than observed for published RNA-Seq analysis (45.8% vs. 37.5%). These data demonstrate that the Iso-Seq™ approach is useful for detecting AS events. Using the Iso-Seq-defined transcript collection in Amborella as a reference, we further describe a pipeline for detection of AS isoforms from PacBio Iso-Seq™ without using a reference sequence (de novo). Results using this pipeline show a 66%-76% overall success rate in identifying AS events. This de novoAS detection pipeline provides a method to accurately characterize and identify bona fide alternatively spliced transcripts in any nonmodel system that lacks a reference genome sequence. Hence, our pipeline has huge potential applications and benefits to the broader biology community.

Obtaining accurate phylogenies and effective species discrimination using a small standardized set of plastid genes is challenging in evolutionarily young lineages. Complete plastid genome sequencing offers an increasingly easy-to-access source of characters that helps address this. The usefulness of this approach, however, depends on the extent to which plastid haplotypes track morphological species boundaries. We have tested the power of complete plastid genomes to discriminate among multiple accessions of 11 of 13 New Caledonian Araucaria species, an evolutionarily young lineage where the standard DNA barcoding approach has so far failed and phylogenetic relationships have remained elusive. Additionally, 11 nuclear gene regions were Sanger sequenced for all accessions to ascertain the success of species discrimination using a moderate number of nuclear genes. Overall, fewer than half of the New Caledonian Araucaria species with multiple accessions were monophyletic in the plastid or nuclear trees. However, the plastid data retrieved a phylogeny with a higher resolution compared to any previously published tree of this clade and supported the monophyly of about twice as many species and nodes compared to the nuclear data set. Modest gains in discrimination thus are possible, but using complete plastid genomes or a small number of nuclear genes in DNA barcoding may not substantially raise species discriminatory power in many evolutionarily young lineages. The big challenge therefore remains to develop techniques that allow routine access to large numbers of nuclear markers scaleable to thousands of individuals from phylogenetically disparate sample sets.

SignificanceThe last eukaryotic common ancestor had two spliceosomes. The major spliceosome acts on nearly all introns, whereas the minor spliceosome removes rare, U12-type introns. Based on in vitro RNA-splicing assays, the RGH3/ZRSR2 RNA-splicing factor has functions in both spliceosomes. Here, we show that the maize rgh3 mutant allele primarily disrupts U12 splicing, similar to human ZRSR2 mutants, indicating a conserved in vivo function in the minor spliceosome. These mutant alleles block cell differentiation leading to overaccumulation of stem cells in endosperm and blood, respectively. We found extensive conservation between maize and human U12-type intron-containing genes, demonstrating that a common genetic architecture controls at least a subset of cell differentiation pathways in both plants and animals.

Highlights d Autophagy promotes primary tumor growth, yet suppresses metastatic outgrowth d Autophagy deficiency elicits a pro-metastatic basal tumor cell subpopulation d NBR1 accumulation mediates the effects of autophagy inhibition on metastasis d Enforced autophagy induction prevents the outgrowth of disseminated tumor cells