Chromosome-level genome assembly of Cylas formicarius provides insights into its adaptation and invasion mechanisms

Cylasformicarius is one of the most important pests of sweet potato worldwide, causing considerable ecological and economic damage.This study improved the effect of comprehensive management and understanding of genetic mechanisms by examining the functional genomics of C. formicarius.Using Illumina and PacBio sequencing, this study obtained a chromosome-level genome assembly of adult weevils from lines inbred for 15 generations.The high-quality assembly obtained was 338.84 Mb, with contig and scaffold N50 values of 14.97 and 34.23 Mb, respectively.In total, 157.51 Mb of repeat sequences and 11 907 protein-coding genes were predicted.A total of 337.06 Mb of genomic sequences was located on the 11 chromosomes, accounting for 99.03%of the total length of the associated chromosome.Comparative genomic analysis showed that C. formicarius was sister to Dendroctonus ponderosae, and C. formicarius diverged from D. ponderosae approximately 138.89 million years ago (Mya).Many important gene families expanded in the C. formicarius genome were involved in the detoxification of pesticides, tolerance to cold stress and chemosensory system.To further study the role of odorant-binding proteins (OBPs) in olfactory recognition of C. formicarius, the binding assay results indicated that Cfor OBP4–6 had strong binding affinities for sex pheromones and other ligands.The high-quality C. formicarius genome provides a valuable resource to reveal the molecular ecological basis, genetic mechanism, and evolutionary process of major agricultural pests;it also offers new ideas and new technologies for ecologically sustainable pest control.

Overexpression of phosphatidylserine synthase IbPSS1 affords cellular Na+homeostasis and salt tolerance by activating plasma membrane Na^(+)/H^(+)antiport activity in sweet potato roots

Phosphatidylserine synthase(PSS)-mediated phosphatidylserine(PS)synthesis is crucial for plant development.However,little is known about the contribution of PSS to Na^(+)homeostasis regulation and salt tolerance in plants.Here,we cloned the IbPSS1 gene,which encodes an ortholog of Arabidopsis AtPSS1,from sweet potato(Ipomoea batatas(L.)Lam.).The transient expression of IbPSS1 in Nicotiana benthamiana leaves increased PS abundance.We then established an efficient Agrobacterium rhizogenes-mediated in vivo root transgenic system for sweet potato.Overexpression of IbPSS1 through this system markedly decreased cellular Na^(+)accumulation in salinized transgenic roots(TRs)compared with adventitious roots.The overexpression of IbPSS1 enhanced salt-induced Na^(+)/H^(+)antiport activity and increased plasma membrane(PM)Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the TRs.We confirmed the important role of IbPSS1 in improving salt tolerance in transgenic sweet potato lines obtained from an Agrobacterium tumefaciens-mediated transformation system.Similarly,compared with the wild-type(WT)plants,the transgenic lines presented decreased Na^(+)accumulation,enhanced Na^(+)exclusion,and increased PM Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the roots.Exogenous application of lysophosphatidylserine triggered similar shifts in Na^(+)accumulation and Na^(+)and Ca^(2+)fluxes in the salinized roots of WT.Overall,this study provides an efficient and reliable transgenic method for functional genomic studies of sweet potato.Our results revealed that IbPSS1 contributes to the salt tolerance of sweet potato by enabling Na^(+)homeostasis and Na^(+)exclusion in the roots,and the latter process is possibly controlled by PS reinforcing Ca^(2+)signaling in the roots.

Genome-wide analysis of expression quantitative trait loci(eQTLs)reveals the regulatory architecture of gene expression variation in the storage roots of sweet potato

Dissecting the genetic regulation of gene expression is critical for understanding phenotypic variation and species evolution.However,our understanding of the transcriptional variability in sweet potato remains limited.Here,we analyzed two publicly available datasets to explore the landscape of transcriptomic variations and its genetic basis in the storage roots of sweet potato.The comprehensive analysis identified a total of 724,438 high-confidence single nucleotide polymorphisms(SNPs)and 26,026 expressed genes.Expression quantitative trait locus(eQTL)analysis revealed 4408 eQTLs regulating the expression of 3646 genes,including 2261 local eQTLs and 2147 distant eQTLs.Two distant eQTL hotspots were found with target genes significantly enriched in specific functional classifications.By combining the information from regulatory network analyses,eQTLs and association mapping,we found that IbMYB1-2 acts as a master regulator and is the major gene responsible for the activation of anthocyanin biosynthesis in the storage roots of sweet potato.Our study provides the first insight into the genetic architecture of genome-wide expression variation in sweet potato and can be used to investigate the potential effects of genetic variants on key agronomic traits in sweet potato.

The trivalent cerium-induced cell death and alteration of ion flux in sweetpotato [Ipomoea batatas(L.) Lam]

The rare earth element cerium（Ce） in its several forms is extensively utilized in various fields, including nano-technology, agriculture, and the food industry. Due to its increasing unregulated usage, Ce is now a potential source of pollution and toxicity due to its excessive environmental accumulation. Unfortunately, analysis of the toxic effects of Ce in plants is still in its early stages. Herein, we investigated the effects of Ce3＋ treatment on development-related indicators in sweetpotato. We found that a low concentration（10 mg/L） slightly improved oxidation resistance, while a high concentration（20-80 mg/L）negatively affected development and photosynthesis and triggered increases in reactive oxygen species（ROS） production, antioxidant enzyme activities, and malondialdehyde（MDA） content. Moreover,elevation and efflux of cytosolic Ca^（2＋） and caspase-l-like activity were induced by high-concentration Ce^（3＋） treatment. Finally, cell viability decreased as Ce3＋ concentration increased. These results suggest that（1） a high Ce3＋ concentration（20-80 mg/L） inhibits development and photosynthesis of sweetpotato and induces oxidative damage followed by lipid peroxidation in the root,（2） a caspase-l-like protease is induced by cytosolic Ca^（2＋） and ROS overproduction to cause programmed cell death in the root, and（3） a high concentration of Ce3＋ could trigger a hypothetical cell death pathway, wherein Ce3＋induces ROS production followed by cytosolic Ca^（2＋） elevation, which activates caspase-l-like activity,which in turn leads to programmed cell death in the root of sweetpotato.