Several studies have shown that tRNAs can be enzymatically cleaved to generate distinct classes of tRNA-derived fragments (tRF). Here, we report that tRF/miR-1280, a 17-bp fragment derived from tRNA and pre-miRNA, influences Notch signaling pathways that support the function of cancer stem-like cells (CSC) in colorectal cancer progression. tRF/miR-1280 expression was decreased in human specimens of colorectal cancer. Ectopic expression of tRF/miR-1280 reduced cell proliferation and colony formation, whereas its suppression reversed these effects. Mechanistic investigations implicated the Notch ligand JAG2 as a direct target of tRF/miR-1280 binding through which it reduced tumor formation and metastasis. Notably, tRF/miR-1280-mediated inactivation of Notch signaling suppressed CSC phenotypes, including by direct transcriptional repression of the Gata1/3 and miR-200b genes. These results were consistent with findings of decreased levels of miR-200b and elevated levels of JAG2, Gata1, Gata3, Zeb1, and Suz12 in colorectal cancer tissue specimens. Taken together, our results established that tRF/miR-1280 suppresses colorectal cancer growth and metastasis by repressing Notch signaling pathways that support CSC phenotypes. Furthermore, they provide evidence that functionally active miRNA can be derived from tRNA, offering potential biomarker and therapeutic uses. .

Bumblebees are a diverse group of globally important pollinators in natural ecosystems and for agricultural food production. With both eusocial and solitary life-cycle phases, and some social parasite species, they are especially interesting models to understand social evolution, behavior, and ecology. Reports of many species in decline point to pathogen transmission, habitat loss, pesticide usage, and global climate change, as interconnected causes. These threats to bumblebee diversity make our reliance on a handful of well-studied species for agricultural pollination particularly precarious. To broadly sample bumblebee genomic and phenotypic diversity, we de novo sequenced and assembled the genomes of 17 species, representing all 15 subgenera, producing the first genus-wide quantification of genetic and genomic variation potentially underlying key ecological and behavioral traits. The species phylogeny resolves subgenera relationships while incomplete lineage sorting likely drives high levels of gene tree discordance. Five chromosome-level assemblies show a stable 18-chromosome karyotype, with major rearrangements creating 25 chromosomes in social parasites. Differential transposable element activity drives changes in genome sizes, with putative domestications of repetitive sequences influencing gene coding and regulatory potential. Dynamically evolving gene families and signatures of positive selection point to genus-wide variation in processes linked to foraging, diet and metabolism, immunity and detoxification, as well as adaptations for life at high altitudes. Our study reveals how bumblebee genes and genomes have evolved across the Bombus phylogeny and identifies variations potentially linked to key ecological and behavioral traits of these important pollinators.

The domestic silkworm, Bombyx mori, is a model insect with important economic value for silk production that also acts as a bioreactor for biomaterial production. The functional complexity of the silkworm transcriptome has not yet been fully elucidated, although genomic sequencing and other tools have been widely used in its study. We explored the transcriptome of silkworm at different developmental stages using high-throughput paired-end RNA sequencing. A total of about 3.3 gigabases (Gb) of sequence was obtained, representing about a 7-fold coverage of the B. mori genome. From the reads that were mapped to the genome sequence; 23,461 transcripts were obtained, 5,428 of them were novel. Of the 14,623 predicted protein-coding genes in the silkworm genome database, 11,884 of them were found to be expressed in the silkworm transcriptome, giving a coverage of 81.3%. A total of 13,195 new exons were detected, of which, 5,911 were found in the annotated genes in the Silkworm Genome Database (SilkDB). An analysis of alternative splicing in the transcriptome revealed that 3,247 genes had undergone alternative splicing. To help with the data analysis, a transcriptome database that integrates our transcriptome data with the silkworm genome data was constructed and is publicly available at http://124.17.27.136/gbrowse2/. To our knowledge, this is the first study to elucidate the silkworm transcriptome using high-throughput RNA sequencing technology. Our data indicate that the transcriptome of silkworm is much more complex than previously anticipated. This work provides tools and resources for the identification of new functional elements and paves the way for future functional genomics studies.