The insect fat body is comparable to the liver and adipose tissue in vertebrates, and plays a pivotal role in energy metabolism, nutrient storage, and reproduction. During metamorphosis, the fat body is disassembled via programmed cell death and cell dissociation. After adult eclosion, the fat body is reconstructed either by repopulation from the remaining juvenile fat body cells or by differentiation from adult progenitor cells. This reconstruction is a prerequisite for initiating the extensive synthesis of vitellogenin (Vg), which is necessary for the maturation of eggs. Despite its significance, the underlying mechanisms of this reconstruction remain inadequately understood. Transcriptome analysis of the fat bodies from migratory locusts at 0–5 days post adult emergence revealed 79 genes associated with chromatin remodeling. Weighted gene co-expression network analysis indicated a positive correlation between chromatin remodeling and fat body reconstitution. Protein–protein interaction analysis revealed that brahma, which encodes the catalytic subunit of the SWI/SNF chromatin remodeling complex, is crucial for post-adult-eclosion fat body development. qRT-PCR analysis demonstrated that the levels of brahma mRNA in the fat body are progressively increased during the previtellogenic stage, then reach the peak and remain elevated in the vitellogenic phase. Furthermore, brahma is expressed in response to gonadotropic juvenile hormone (JH). Knockdown of brahma led to a marked reduction in Vg expression within the fat body, along with arrested ovarian growth. These findings shed light on the involvement of brahma-mediated chromatin remodeling in JH-stimulated fat body reconstruction and reproduction of adult female locusts.

CRISPR/Cas9-based gene editing research has advanced greatly and shows broad potential for practical application in life sciences, but the Cas9 system is often constrained by the requirement of a protospacer adjacent motif (PAM) at the target site. While xCas9, a variant derived from Streptococcus pyogenes Cas9 (SpCas9), can recognize a broader range of PAMs, its application in non-model insects is lacking. In this study, we explored xCas9 activity in gene editing by selecting corazonin (Crz) and the target sites with various PAMs in Locusta migratoria, a destructive insect pest worldwide. We found that xCas9 could cleave the target site with AG PAM while SpCas9 could not, although xCas9 appeared to have lower activity than SpCas9 at the canonical NGG PAMs. The heritable homozygous Crz^–/– locust strain was generated by the application of xCas9. The Crz^–/– strain showed an albino body color, with significantly downregulated expression of several body color-related genes including Pale, Vermilion, Cinnabar, White and β-carotene-binding protein. In addition, Crz^–/– mutants exhibited significantly reduced expression of Chitin synthase 1, along with a markedly lower chitin content as well as compact and rigid cuticles. Furthermore, Crz^–/– mutants displayed impaired performance under low-temperature stress, including prolonged lifespan, reduced body weight and smaller body size. Our results suggest that xCas9 is effective for insect genome editing, and Crz plays essential roles in insect body color, cuticle development and adaptation to low-temperature stress. The findings of this study extend the application of xCas9 in non-model insects and provide new insights into our understanding of the regulation of insect cuticle development and environmental adaptation.