Mitochondrial (mt) genomes of animals typically contain 37 genes for 13 proteins, two ribosomal RNA (rRNA) genes and 22 transfer RNA (tRNA) genes. In sarcoptiform mites, the entire set of mt tRNA genes is present in Aleuroglyphus ovatus, Caloglyphus berlesei, Dermatophagoides farinae, D. pteronyssinus, Histiostoma blomquisti and Psoroptes cuniculi. Loss of 16 mt tRNA genes, however, was reported in Steganacarus magnus; loss of 2–3 tRNA genes was reported in Tyrophagus longior, T. putrescentiae and Sarcoptes scabiei. Nevertheless, convincing evidence for mt gene loss is lacking in these mites. We sequenced the mitochondrial genomes of two sarcoptiform mites, Histiostoma feroniarum (13,896 bp) and Rhizoglyphus robini (14,244 bp). Using tRNAScan and ARWEN programs, we identified 16 and 17 tRNA genes in the mt genomes of H. feroniarum and R. robini, respectively. The other six mt tRNA genes in H. feroniarum and five mt tRNA genes in R. robini can only be identified manually by sequence comparison when alternative anticodons are considered. We applied this manual approach to other mites that were reported previously to have lost mt tRNA genes. We were able to identify all of the 16 mt tRNA genes that were reported as lost in St. magnus, two of the three mt tRNA genes that were reported as lost in T. longior and T. putrescentiae, and the two mt tRNA genes that were reported as lost in Sa. scabiei. All of the tRNA genes inferred from these manually identified genes have truncation in the arms and mismatches in the stems. Our results reveal very unconventional tRNA structures in sarcoptiform mites and do not support the loss of mt tRNA genes in these mites. The functional implication of the drastic structural changes in these tRNA genes remains to be investigated.

Volvariella volvacea, the Chinese mushroom, is a high-temperature grass-rot fungus with great production potential, yet its low yield limits industrial development. Exogenous sodium acetate (NaAc) has been shown to increase yield by promoting indole-3-acetic acid (IAA) synthesis during the primordium stage, but the underlying mechanism remains unclear. In this study, the aldehyde dehydrogenase gene VvALDH, highly expressed at the primordium stage, was cloned and functionally characterized. VvALDH encodes a 1509 bp cDNA with a conserved aldehyde dehydrogenase domain. Using Agrobacterium-mediated transformation, overexpression lines showed a 4.76-fold increase in VvALDH expression, accompanied by higher biomass (38%), yield (83%), and IAA content (34%), while RNAi lines showed opposite trends. These results demonstrate that VvALDH promotes IAA biosynthesis, enhances primordium differentiation, and increases yield. Further analysis revealed its involvement in multiple IAA biosynthetic pathways, including indolepyruvate, tryptamine, and tryptophan side-chain oxidase pathways. This work clarifies the molecular basis of NaAc-mediated yield improvement and provides a theoretical foundation for genetic and cultivation strategies in V. volvacea.

Pleurotus ostreatus cultivation is often affected by pest infestations, which contaminate the bag by eating nutrients and mycelium. This contamination eventually leads to a decline in the quality and yield of edible mushrooms and affects farmers’ income. Therefore, pesticides are commonly used for pest control. To examine the impact of insecticides on the growth of P. ostreatus, this study quantified the activities of antioxidant enzymes, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine deaminase (PAL), in the mushroom under different insecticide treatments. Additionally, transcriptome sequencing was performed to investigate the underlying regulatory mechanisms. The findings indicated that dinotefuran, diflubenzuron, chlorantraniliprole, and beta-cypermethrin treatments resulted in a significant reduction in catalase and peroxidase activities in P. ostreatus. Conversely, the application of beta-cypermethrin and chlorantraniliprole significantly enhanced PAL and SOD activities in the mycelium. PAL activity was significantly increased in all the mixed substrates, whereas only spray treatments with diflubenzuron resulted in a significant increase in PAL activity. SOD activity in the substrates was reduced by diflubenzuron in the mixed treatment and chlorantraniliprole in the spray treatment. In contrast, all other treatments resulted in a significant increase in SOD activity in the substrates. Transcriptome sequencing revealed that differential genes were predominantly enriched in valine, leucine, and isoleucine degradation, fatty acid degradation, tyrosine metabolism, ascorbate and aldarate metabolism, and histidine metabolism, among others. These biological processes are hypothesized to be involved in the growth regulatory effects of insecticides on the mycelium and ascospores of P. ostreatus. The reliability of the transcriptomic data was also validated through quantitative real-time polymerase chain reaction.

Bradysia difformis is a notorious pest in mushroom production in China. Biological control using Bacillus thuringiensis (Bt) offers an environmentally friendly and effective strategy against this pest. Here, we show that the complete genome of strain JW-1 consists of one circular chromosome and seven circular plasmids. JW-1-Plasmid 4 comprises 127,921 bp with a GC content of 33.9%, and is predicted to contain 131 genes, including six insecticidal genes: cry4Aa, cry4Ba, cry10Ab, cry11Aa, cyt1Aa, and cyt2Ba. A 3542-bp fragment containing the cry4Aa gene was amplified from this strain. Phylogenetic analysis based on Cry4 toxin sequences showed that JW-1 Cry4 toxin belongs to the Cry4Aa toxin cluster. A Cry4Aa fusion protein was subsequently expressed in E. coli and purified using Ni-IDA affinity chromatography. A larval feeding assay showed that purified Cry4Aa was toxic to B. difformis larvae, with an LC₅₀ of 2.71 ng/mL. These results confirmed the identity and bioactivity of Cry4Aa from strain JW-1, offering a promising biological control agent against this major pest.