Sweet orange (Citrus sinensis) is a sub-tropical fruit crop with important economic value that is popular worldwide; however, various pathogens significantly affect citrus cultivation and distribution. AlkB homolog (ALKBH) proteins play crucial roles in RNA metabolism and translation in plants; however, no systematic investigations have been performed on ALKBH in sweet oranges. In this study, ten ALKBH gene family members were identified in Citrus sinensis genome. Standardized analyses, including physical properties, phylogenetic analysis, gene structure, motif composition, cis-acting element prediction, chromosome distribution, and synteny analysis, were conducted. The phylogenetic analysis suggested that the ten proteins were clustered into three groups, each of which had similar motifs and gene structures. Gene expression profiling revealed that almost all CsALKBH proteins were highly expressed in callus, and ALKBH9/10-like group members responded positively to biotic stress. Overall, this study is the first to report a genome-wide assessment of the ALKBH family in sweet oranges and provides valuable insights for candidate gene selection and elucidating the molecular mechanism of sweet orange response to pathogenic infections.

Citrus leaf blotch virus (CLBV) is a positive-sense single-stranded RNA virus belonging to the genus Citrivirus within the family Betaflexiviridae. It infects a broad range of economically significant fruit crops, including citrus, kiwifruit, and apple. Surveys conducted in the field have documented appreciable incidence rates in several hosts, thereby emphasizing its emerging threat to global pomiculture. Comprehensive surveillance of CLBV genetic diversity is indispensable for predicting strain-specific epidemics and designing durable, broadly protective control strategies. Current surveys of CLBV diversity are still gene-fragment-centric, with whole-genome resolution remaining largely untapped. In this study, an analysis of codon usage bias analysis was performed using all available CLBV full-length genomes. The findings revealed that CLBV exhibits low codon usage bias, with natural selection, rather than mutational drift, being the primary driver. Phylogenetic analysis has been demonstrated to categorize isolates according to their host of origin rather than their geographical location. This observation suggests that host adaptation may supersede spatial structure in CLBV evolution and reinforce natural selection as the dominant force shaping its codon usage landscape. From the perspective of the codon adaptation index, Prunus avium is the host that exerts the greatest influence on the formation of its codon usage bias. The present study provides the first genome-wide portrait of CLBV codon usage bias, offering a robust framework for future investigations into its origin and evolutionary dynamics.

The endoplasmic reticulum (ER) stress response, or unfolded protein response (UPR), is crucial for cellular homeostasis and host defense. Its role in insect vectors of plant pathogens remains poorly understood. This study conducted a comprehensive molecular characterization of three core UPR genes—BiP, IRE1, and XBP1—in Diaphorina citri, the insect vector of the citrus huanglongbing pathogen Candidatus Liberibacter asiaticus (CLas). Expression profiling showed distinct developmental and tissue-specific patterns for these genes. The IRE1-mediated unconventional splicing of XBP1 mRNA was identified in D. citri and predicted across diverse insect pests. A semi-quantitative RT-PCR assay was established to detect this splicing event for monitoring ER stress. Time-course analysis of CLas-infected D. citri revealed an early activation (upregulation of BiP, IRE1, XBP1 transcripts, and increased XBP1 splicing) followed by later suppression of the UPR. Functional studies demonstrated that induction of ER stress with thapsigargin increased CLas titer. RNAi-mediated silencing showed that IRE1 silencing increased CLas proliferation, whereas XBP1 silencing reduced it. These findings provide foundational insights into the ER stress pathway in D. citri and demonstrate that the IRE1-XBP1 branch of the UPR plays a critical role in modulating CLas infection dynamics within its insect vector.

Diaphorina citri Kuwayama is the primary natural vector of citrus Huanglongbing (HLB). Prolonged use of chemical pesticides leads to insect resistance, reduces control efficacy, and causes ecological pollution. RNA interference (RNAi) enables sequence-specific gene silencing, representing a promising precision strategy for managing D. citri. This review summarizes advances in RNAi-based control of D. citri, focusing on three groups of target gene screening strategies based on essential functional genes, behavioral regulation genes, and D. citri-Candidatus Liberibacter asiaticus (CLas) interaction genes. It also compares double-stranded RNA (dsRNA) delivery systems and highlights key bottlenecks, including poor stability, inefficient delivery, off-target effects, and resistance evolution. Future research should focus on optimizing target gene screening, developing efficient delivery systems, and enhancing ecological safety assessments. Integrating RNAi technology with various environmentally friendly management strategies will advance the sustainable control of D. citri and citrus HLB.