Main conclusion: This review aims to describe the main genetic adaptations of plants to abiotic and biotic stressors in urban landscapes through modulation of gene expression and genotypic changes. Urbanization deeply impacts biodiversity through ecosystem alteration and habitat fragmentation, creating novel environmental challenges for plant species. Plants have evolved cellular, molecular, and biochemical strategies to cope with the diverse biotic and abiotic stresses associated with urbanization. However, many of these defense and resistance mechanisms remain poorly understood. Addressing these knowledge gaps is crucial for advancing our understanding of urban biodiversity and elucidating the ecological and evolutionary dynamics of species in urban landscapes. As sessile organisms, plants depend heavily on modifications in gene expression as a rapid and efficient strategy to survive urban stressors. At the same time, the urban environment pressures induced plant species to evolve genotypic adaptations that enhance their survival and growth in these contexts. This review explores the different genetic responses of plants to urbanization. We focus on key abiotic challenges, such as air pollution, elevated CO₂ levels, heavy metal contamination, heat and drought stress, salinity, and biotic stresses caused by herbivorous insects. By examining these genetic mechanisms induced by urban stressors, we aim to analyze the molecular pathways and genetic patterns underlying the adaptation of plant species to urban environments. This knowledge is a valuable tool for enhancing the selection and propagation of adaptive traits in plant populations, supporting species conservation efforts, and promoting urban biodiversity.

Females of the Mediterranean fruit fly Ceratitis capitata (Medfly) are major agricultural pests, as they lay eggs into the fruit crops of hundreds of plant species. In Medfly, female sex determination is based on the activation of Cctransformer (Cctra). A maternal contribution of Cctra is required to activate Cctra itself in the XX embryos and to start and epigenetically maintain a Cctra positive feedback loop, by female-specific alternative splicing, leading to female development. In XY embryos, the male determining Maleness-on-the-Y gene (MoY) blocks this activation and Cctra produces male-specific transcripts encoding truncated CcTRA isoforms and male differentiation occurs. With the aim of inducing frameshift mutations in the first coding exon to disrupt both female-specific and shorter male-specific CcTRA open reading frames (ORF), we injected Cas9 ribonucleoproteins (Cas9 and single guide RNA, sgRNA) in embryos. As this approach leads to mostly monoallelic mutations, masculinization was expected only in G1 XX individuals carrying biallelic mutations, following crosses of G0 injected individuals. Surprisingly, these injections into XX-only embryos led to G0 adults that included not only XX females but also 50% of reverted fertile XX males. The G0 XX males expressed male-specific Cctra transcripts, suggesting full masculinization. Interestingly, out of six G0 XX males, four displayed the Cctra wild type sequence. This finding suggests that masculinization by Cas9-sgRNA injections was independent from its mutagenic activity. In line with this observation, embryonic targeting of Cctra in XX embryos by a dead Cas9 (enzymatically inactive, dCas9) also favoured a male-specific splicing of Cctra, in both embryos and adults. Our data suggest that the establishment of Cctra female-specific autoregulation during the early embryogenesis has been repressed in XX embryos by the transient binding of the Cas9-sgRNA on the first exon of the Cctra gene. This hypothesis is supported by the observation that the shift of Cctra splicing from female to male mode is induced also by dCas9. Collectively, the present findings corroborate the idea that a transient embryonic inactivation of Cctra is sufficient for male sex determination.

Ceratitis capitata, known as the Mediterranean fruit fly (Medfly), is a major dipteran pest significantly impacting fruit and vegetable farming. Currently, its control heavily relies mainly on chemical insecticides, which pose health risks and have effects on pollinators. A more sustainable and species-specific alternative strategy may be based on double-stranded RNA (dsRNA) delivery through feeding to disrupt essential functions in pest insects, which is poorly reported in dipteran species. Previous reports in Orthoptera and Coleoptera species suggested that dsRNA degradation by specific nucleases in the intestinal lumen is among the major obstacles to feeding-mediated RNAi in insects. In our study, we experimented with three-day adult feeding using a combination of dsRNA molecules that target the expression of the ATPase vital gene and two intestinal dsRNA nucleases. These dsRNA molecules were recently tested separately in two Tephritidae species, showing limited effectiveness. In contrast, by simultaneously feeding dsRNA against the CcVha68-1, CcdsRNase1, and CcdsRNase2 genes, we observed 79% mortality over seven days, which was associated with a decrease in mRNA levels of the three targeted genes. As expected, we also observed a reduction in dsRNA degradation following RNAi against nucleases. This research illustrates the potential of utilizing molecules as pesticides to achieve mortality rates in Medfly adults by targeting crucial genes and intestinal nucleases. Furthermore, it underscores the importance of exploring RNAi-based approaches for pest management.

An undescribed 5,6-dihydropyran-2-one, namely diplopyrone C, was isolated and characterized from the cultures of an isolate of the fungus Diplodia corticola recovered from Quercus suber in Algeria. The structure and relative stereostructure of (5S,6S,7Z,9S,10S)-5-hydroxy-6-(2-(3-methyloxiran-2-yl)vinyl)-5,6-dihydro-2H-pyran-2-one were assigned essentially based on NMR and MS data. Furthermore, ten known compounds were isolated and identified in the same cultures. The most abundant product, the tetracyclic pimarane diterpene sphaeropsidin A, was tested for insecticidal effects against the model sucking aphid, Acyrthosiphon pisum. Results showed a toxic dose-dependent oral activity of sphaeropsidin A, with an LC₅₀ of 9.64 mM.

Sphaeropsidin A (SphA) is a pimarane diterpene produced by several fungi associated with plants. Following previous evidence of insecticidal properties of SphA, we investigated its contact and oral toxicity against the model chewing lepidopteran Spodoptera littoralis. The compound showed no lethal effect when directly sprayed on larvae, while it produced an evident oral toxic effect, associated with sublethal effects. These results demonstrated that SphA might play a defensive role against lepidopteran insects in plants harboring the producing fungus, depending on the extent at which the endophytic strains are able to perform biosynthesis of this and eventually other bioactive metabolites in vivo.

The Asian tiger mosquito, Aedes albopictus, is an invasive species and a vector for several significant human pathogens. Gaining a deeper understanding of its reproductive biology offers valuable insights into its evolutionary success and may inform the development of sustainable strategies to control its spread. This study presents a comprehensive structural and functional characterization of the fruitless gene in Ae. albopictus (Aalfru), a pivotal regulator of sexual behavior in insects. Through in silico analysis combined with molecular and functional genetics approaches, we identified a high degree of conservation in the fru gene structure and its regulation via sex-specific alternative splicing. Differently from Drosophila, Aedes aegypti, and other dipteran fruitless orthologs, Aalfru sex-specific regulation starts in 1-day-old embryos, rather than the late larval stage. Functional analysis using embryonic RNA interference (RNAi) demonstrated that, Ae. albopictus males with transiently disrupted fru expression at the embryonic stage showed significant deficits in adult mating behavior and failed to produce viable progeny. Our findings elucidate the Aalfru gene’s molecular organization, developmental regulation, and critical role in courtship behavior, highlighting its importance in male sexual behavior and reproductive success in Ae. albopictus.