Functional Analyses in the Silkworm,Bombyx mori, Support a Role for Notch Signaling in Appendage Development But Not theGroucho‐Dependent Pair‐Rule Process

Abstract

Pair-rule genes are crucial for generating dual segment periodicity for body plan patterning in Drosophila. Bombyx mori is an intermediate germband insect, in which the formation of posterior segments via sequential addition follows a different process from that in Drosophila, although it is somewhat comparable to the process that occurs in vertebrates. Notch signaling is involved in the segmentation of vertebrates, spiders, and basal insects. Groucho (Gro) participates in Notch signaling as a corepressor and plays an important role during segmentation by interacting with other pair-rule proteins. Here, we cloned a gro homolog in the silkworm and positioned it at chromosome 21 in the genetic linkage map. Functional analyses of Bmgro and Bmnotch during embryogenesis were conducted using RNA interference (RNAi). Depletion of Bmgro led to a loss of odd-numbered segments, a characteristic pair-rule phenotype. Bmnotch RNAi resulted in that paired appendages on each segment were symmetrically fused along the ventral midline. An individual segment seemed to possess only one segmental appendage when Notch signaling was compromised. Irregular segments were observed in the Bmnotch RNAi embryo. Our results show that the involvement of Bmgro during the pair-rule process is not mediated by Notch signaling in silkworm. Notch signaling remains in appendage segmentation and restriction of cell fate.

The extramacrochaetae gene is required for blastokinesis in silkworm, Bombyx mori

“…Embryos of the same stage from the control injected with EGFP dsRNA developed normally (Supplementary Material Table S4). Furthermore, the unique phenotypes obtained after injection with Bmemc dsRNA were distinct from the RNAi knockdown phenotypes for other genes reported previously (Liu, , ), suggesting a gene‐specific effect. RT‐PCR results also warranted that the expression of Bmemc was depleted (Fig.…”

Superoxide dismutase down-regulation and the oxidative stress is required to initiate pupation in Bombyx mori

“…We also identified the Hippo and TGF-beta signaling pathways as common pathways in the fourth molting stage and the pupal stages. The Notch signaling pathway is involved not only in the development 22–24 but also in controlling the generation of ROS 25–27 . The Hippo signaling pathway induces apoptosis in the insect 28 , also apoptosis is induced in the fat body of the B. mori pre-pupa 29,30 .…”

The Ubiquitin Conjugating Enzyme UbcD1 is Required for Notch Signaling Activation During Drosophila Wing Development

“…Notch signaling regulates wing margin formation in Drosophila hydei ( Van Breugel and Langhout, 1983 ) and sheep blowfly ( Davies et al, 1996 ; Chen et al, 1998 ), wing morphogenesis in silkworm ( Sato et al, 2008 ; Ling et al, 2015 ) and pigment patterns in the butterfly wing ( Reed, 2004 ; Reed and Serfas, 2004 ). Further studies indicate that Notch signaling is required for oogenesis in Blattella germanica ( Irles et al, 2016 ) and locust ( Song et al, 2019 ), reproductive constraint in the adult worker honeybee ( Duncan et al, 2016 ), appendage development in silk worm ( Liu, 2012 ) and camouflage patterns in caterpillars ( Jin et al, 2020 ). Recent studies reveal crucial role of Notch signaling during body segmentation in insect species such as cockroaches ( Pueyo et al, 2008 ; Chesebro et al, 2013 ) and silkworm ( Liu, 2013 ).…”