Inulin is an important reserve polysaccharide in Asteraceae plants, and is also widely used as a sweetener, a source of dietary fibre and prebiotic. Nevertheless, a lack of genomic resources for inulin‐producing plants has hindered extensive studies on inulin metabolism and regulation. Here, we present chromosome‐level reference genomes for four inulin‐producing plants: chicory (Cichorium intybus), endive (Cichorium endivia), great burdock (Arctium lappa) and yacon (Smallanthus sonchifolius), with assembled genome sizes of 1.28, 0.89, 1.73 and 2.72 Gb, respectively. We found that the chicory, endive and great burdock genomes were shaped by whole genome triplication (WGT‐1), and the yacon genome was shaped by WGT‐1 and two subsequent whole genome duplications (WGD‐2 and WGD‐3). A yacon unique whole genome duplication (WGD‐3) occurred 5.6–5.8 million years ago. Our results also showed the genome size difference between chicory and endive is largely due to LTR retrotransposons, and rejected a previous hypothesis that chicory is an ancestor of endive. Furthermore, we identified fructan‐active‐enzyme and transcription‐factor genes, and found there is one copy in chicory, endive and great burdock but two copies in yacon for most of these genes, except for the 1‐FEH II gene which is significantly expanded in chicory. Interestingly, inulin synthesis genes 1‐SST and 1‐FFT are located close to each other, as are the degradation genes 1‐FEH I and 1‐FEH II. Finally, we predicted protein structures for 1‐FFT genes to explore the mechanism determining inulin chain length.

Background The globe skimmer dragonfly (Pantala flavescens) is a notable Odonata insect distributed in nature fields and farmlands worldwide, and it is commonly recognized as a natural enemy because it preys on agricultural pests and health pests. As one of the sister groups of winged insects, odonatan species are key to understanding the evolution of insect wings. Findings We present a high-quality reference genome of P. flavescens, which is the first chromosome-level genome in the Palaeoptera (Odonata and Ephemeroptera). The assembled genome size was 662 Mb, with a contig N50 of 16.2 Mb. Via Hi-C scaffolding, 648 Mb (97.9%) of contig sequences were clustered, ordered, and assembled into 12 large scaffolds, each corresponding to a natural chromosome. The X chromosome was identified by sequence coverage depth. The repetitive sequences and gene density of the X chromosome are similar to those of autosomal sequences, but the X chromosome shows a much lower degree of heterozygosity. Our analysis shows that the effective population size experienced 3 declining events, which may have been caused by climate change and environmental pollution. Conclusions The genome of P. flavescens provides more information on the biology and evolution of insects and will help for the use of this species in pest control.