Search

SUMMARY: The external appearance of fruit commodities is an essential trait that has profound effects on consumer preferences. A natural melon variety, characterized by an uneven and patchy arrangement of dark green streaks and spots on the white‐skinned rind, resembles shooting stars streaking across the sky; thus, this variety is called "Shooting Star" (SS). To investigate the mechanism underlying the SS melon rind pattern, we initially discovered that the variegated dark green color results from chlorophyll accumulation on the white skin. We then constructed a segregation population by crossing a SS inbred line with a white rind (WR) inbred line and used bulk segregant analysis (BSA) revealed that the SS phenotype is controlled by a single dominant gene, CmAPRR2, which has been previously confirmed to determine dark green coloration. Further genomic analysis revealed a hAT‐like transposable element (TE) inserted in CmAPRR2. This TE in CmAPRR2 is recurrently excised from rind tissues, activating the expression of CmAPRR2. This activation promotes the accumulation of chlorophyll, leading to the variegated dark green color on the rind, and ultimately resulting in the SS rind phenotype. Therefore, we propose that the SS phenotype results from the recurrent excision of the hAT‐like TE in CmAPRR2. Significance Statement: Currently, there are numerous studies on transposons in asexual reproduction, but few focus on their role in sexual reproduction. In this paper, we investigate melon skin color through map‐based cloning to locate the gene responsible for skin color and identify the transposons affecting it. [ABSTRACT FROM AUTHOR]

BackgroundThe whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is among the 100 worst invasive species in the world. As one of the most important crop pests and virus vectors, B. tabaci causes substantial crop losses and poses a serious threat to global food security.ResultsWe report the 615-Mb high-quality genome sequence of B. tabaci Middle East-Asia Minor 1 (MEAM1), the first genome sequence in the Aleyrodidae family, which contains 15,664 protein-coding genes. The B. tabaci genome is highly divergent from other sequenced hemipteran genomes, sharing no detectable synteny. A number of known detoxification gene families, including cytochrome P450s and UDP-glucuronosyltransferases, are significantly expanded in B. tabaci. Other expanded gene families, including cathepsins, large clusters of tandemly duplicated B. tabaci-specific genes, and phosphatidylethanolamine-binding proteins (PEBPs), were found to be associated with virus acquisition and transmission and/or insecticide resistance, likely contributing to the global invasiveness and efficient virus transmission capacity of B. tabaci. The presence of 142 horizontally transferred genes from bacteria or fungi in the B. tabaci genome, including genes encoding hopanoid/sterol synthesis and xenobiotic detoxification enzymes that are not present in other insects, offers novel insights into the unique biological adaptations of this insect such as polyphagy and insecticide resistance. Interestingly, two adjacent bacterial pantothenate biosynthesis genes, panB and panC, have been co-transferred into B. tabaci and fused into a single gene that has acquired introns during its evolution.ConclusionsThe B. tabaci genome contains numerous genetic novelties, including expansions in gene families associated with insecticide resistance, detoxification and virus transmission, as well as numerous horizontally transferred genes from bacteria and fungi. We believe these novelties likely have shaped B. tabaci as a highly invasive polyphagous crop pest and efficient vector of plant viruses. The genome serves as a reference for resolving the B. tabaci cryptic species complex, understanding fundamental biological novelties, and providing valuable genetic information to assist the development of novel strategies for controlling whiteflies and the viruses they transmit.

Apple scab, a fungal disease caused by Venturia inaequalis , leads to losses in both yield and fruit quality of apples (Malus domestica Borkh.). Most commercial apple cultivars, including those containing the well-characterized Rvi6- scab-resistance locus on linkage group (LG) 1, are susceptible to scab. HcrVf2 and HcrVf1 are considered the main paralogs of the Rvi6 locus. The major apple scab-resistance loci Vhc1 in "Honeycrisp" and Rvi17 in "Antonovka," were identified in close proximity to HcrVf2. In this study, we used long-read sequencing and in silico gene sequence characterization to identify candidate resistance genes homologous to HcrVf2 and HcrVf1 in Honeycrisp and Antonovka. Previously published chromosome-scale phased assembly of Honeycrisp and a newly assembled phased genome of Antonovka 172670-B were used to identify HcrVf2 and HcrVf1 homologs spanning Vhc1 and Rvi17 loci. In combination with 8 available Malus assemblies, 43 and 46 DNA sequences highly homologous to HcrVf2 and HcrVf1 , respectively, were identified on LG 1 and 6, with identity and coverage ranging between 87–95 and 81–95%, respectively. Among these homologs, 2 candidate genes in Antonovka and Honeycrisp haplome A are located in close physical proximity to the scab-resistance marker Ch-Vf1 on LG 1. They showed the highest identity and coverage (95%) of HcrVf2 and only minor changes in the protein motifs. They were identical by state between each other, but not with HcrVf2. This study offers novel genomic resources and insights into the Vhc1 and Rvi17 loci on LG 1 and identifies candidate genes for further resistance characterization. [ABSTRACT FROM AUTHOR]