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Transgene-based genetic sexing methods are being developed for insects of agricultural and public health importance. Male-only rearing has long been sought in sericulture because males show superior economic characteristics, such as better fitness, lower food consumption, and higher silk yield. Here we report the establishment of a transgene-based genetic sexing system for the silkworm, Bombyx mori. We developed a construct in which a positive feedback loop regulated by sex-specific alternative splicing leads to high-level expression of the tetracycline-repressible transactivator in females only. Transgenic animals show female-specific lethality during embryonic and early larval stages, leading to male-only cocoons. This transgene-based female-specific lethal system not only has wide application in sericulture, but also has great potential in lepidopteran pest control.Lepidoptera | doublesex T he mulberry silkworm, Bombyx mori, is a completely domesticated insect and is the foundation of sericulture, an endeavor of great economic importance. It is believed that sericulture originated in China and has been conducted there for more than 5,000 y (1). Male-only rearing techniques for B. mori are desirable because males show higher resistance to disease, lower food consumption, and better silk quality (2). To this end, several B. mori strains for male-only rearing have been developed by classical genetics. In the last century, Strunnikov (3) established a sex-linked, balanced-lethal system using radiation-induced chromosome translocations. However, conventional approaches involving selective breeding or irradiation for developing male-only silkworm strains are time and labor consuming. Thus, novel approaches are desired to improve modern silkworm breeding. In recent years, advances in B. mori genetic manipulation, notably genetic transformation, have been successfully established and applied extensively in gene function analysis and the production of bioreactors (1, 4-7). These technologies provide a potential basis for improvements in sericulture including the development of a male-only rearing system.Transgene-based genetic sexing systems have been developed in Drosophila melanogaster (8, 9) and several medically and agriculturally important insect species (10-13) as part of a series of genetics-based improvements and alternatives to the sterile insect technique (14). Systems based on sex-specific lethality for improving silk production are preferable to those using differential expression of a marker gene, for example fluorescence, which then would require manual or automated examination of each individual as part of the sorting process. Molecular designs developed for Diptera should be able to provide genetic sexing in B. mori, as the ability to transfer systems from one species to another is a key advantage of transgenic approaches over classical genetic methods (14-16). Furthermore, despite early reports to the contrary, more recent work has established clearly that transgenic strains can be developed with good...

A stimuli‐responsive polymeric prodrug‐based nanotheranostic system with imaging agents (cyanine5.5 and gadolinium‐chelates) and a therapeutic agent paclitaxel (PTX) is prepared via polymerization and conjugating chemistry. The branched polymeric PTX‐Gd‐based nanoparticles (BP‐PTX‐Gd NPs) demonstrate excellent biocompatibility, and high stability under physiological conditions, but they stimuli‐responsively degrade and release PTX rapidly in a tumor microenvironment. The in vitro behavior of NPs labeled with fluorescent dyes is effectively monitored, and the NPs display high cytotoxicity to 4T1 cells similar to free PTX by impairing the function of microtubules, downregulating anti‐apoptotic protein Bcl‐2, and upregulating the expression of Bax, cleaved caspase‐3, cleaved caspase‐9, cleaved‐PARP, and p53 proteins. Great improvement in magnetic resonance imaging (MRI) is demonstrated by these NPs, and MRI accurately maps the temporal change profile of the tumor volume after injection of NPs and the tumor treatment process is also closely correlated with the T1 values measured from MRI, demonstrating the capability of providing real‐time feedback to the chemotherapeutic treatment effectiveness. The imaging‐guided chemotherapy to the 4T1 tumor in the mice model achieves an excellent anti‐tumor effect. This stimuli‐responsive polymeric nano‐agent opens a new door for efficient breast cancer treatment under the guidance of fluorescence/MRI.

The DM domain genes, doublesex (dsx) in insects, or their structural homologs, male abnormal 3 (mab-3) in nematodes and Dmrt1 (doublesex and mab-3-related transcription factor 1) in mammals, are downstream regulators of the sex determination pathway that control sexually dimorphic development. Despite the functional importance of dsx and its potential applications in sterile insect technologies (SITs), the mechanisms by which it controls sexually dimorphic traits and the subsequent developmental gene networks in insects are poorly understood. Phylogenetic analyses indicate that insect dsx genes have sex-specific alternative splicing isoforms, whereas other taxa do not. We exploited genome editing and transgenesis technologies to induce mutations in either the male-specific isoform (dsx) or common region (dsx) of dsx in the somatic tissues of the lepidopteran model insect Bombyx mori. Disruptions of gene function produced either male-specific sexually-dimorphic defects or intersexual phenotypes; these results differ from those observed in other insects, including Drosophila melanogaster. Our data provide insights into the divergence of the insect sex determination pathways related to the most conserved downstream component dsx.

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Insect development and metamorphosis are regulated by two major hormones, juvenile hormone and ecdysteroids. Despite being the key regulator of insect developmental transitions, the metabolic pathway of the primary steroid hormone, 20-hydroxyecdysone (20E), especially its inactivation pathway, is still not completely elucidated. A cytochrome P450 enzyme, CYP18A1, has been shown to play key roles in insect steroid hormone inactivation through 26-hydroxylation. Here, we identified two CYP18 (BmCYP18A1 and BmCYP18B1) orthologs in the lepidopteran model insect, Bombyx mori. Interestingly, BmCYP18A1 gene is predominantly expressed in the middle silk gland (MSG) while BmCYP18B1 expresses ubiquitously in B. mori. BmCYP18A1 is induced by 20E in vitro, suggesting its role in 20E metabolism. Using the binary Gal4/UAS transgenic system, we ectopically overexpressed BmCYP18A1 in a MSG-specific manner with a Sericin1-Gal4 (Ser-Gal4) driver or in a ubiquitous manner with an Actin3-Gal4 (A3-Gal4) driver. Ectopic overexpression of BmCYP18A1 in MSG or in all tissues resulted in developmental arrestment of transgenic animals during the final instar larval stage. The 20E titers in the transgenic animals expressing BmCYP18A1 were lower compared to the levels in the control animals. Although the biological significance of MSG-specific expression of BmCYP18A1 is unclear, our results provide the first evidence that BmCYP18A1, which is conserved in most arthropods, is involved in a tissue-specific steroid hormone inactivation in B. mori.