Xinxin Shangguan

Members of the yellow gene family encode conserved Yellow proteins with diverse roles in insect pigmentation, cuticle formation, and reproduction, making them promising targets for RNA interference (RNAi)-mediated pest control strategies. However, little is known about their phylogeny and functions in the brown planthopper (Nilaparvata lugens), a devastating rice pest that serves as a vector for viral rice diseases. Here, we identified and characterized 11 yellow genes in N. lugens, which showed distinct structures and expression profiles. Phylogenetic analysis revealed that N. lugens has retained orthologs of yellow-y, -b, -d, -e, -g, -g2, -h, and -x but lacks those of yellow-c and -f, suggesting lineage-specific gene loss. Nine of the eleven NlYellow genes were localized to chromosome 8, with several positioned in close genomic proximity. The clustering of these loci suggests that tandem duplication events contributed to the expansion of the NlYellow gene family. NlYellow-b exhibited the highest transcript levels among all identified NlYellow genes, particularly in the female ovipositor, and functional characterization via RNAi revealed that it is essential for molting, wing development, and female fertility. Knockdown of NlYellow-b in fourth-instar nymphs caused lethal molting defects and wing malformation and significantly reduced offspring production. These findings highlight the dual roles of NlYellow-b in development and reproduction, advance our understanding of yellow gene function in insects and highlight NlYellow-b as a candidate for RNAi-based management of N. lugens.

The interplay between phosphate (Pi) signaling and defense pathways is crucial for plant fitness, yet its molecular basis, particularly in wheat, remains poorly understood. Here, we functionally characterized the plasma membrane-localized high-affinity phosphate transporter TaPT3-2D and demonstrated its essential roles in Pi uptake, arbuscular mycorrhizal (AM) symbiosis, and fungal disease resistance. Quantitative analyses showed that TaPT3-2D expression was strongly induced by AM colonization (165-fold increase) and by infection with Bipolaris sorokiniana (54-fold increase) and Gaeumannomyces tritici (15-fold increase). In contrast, virus-induced gene silencing (VIGS) of TaPT3-2D reduced Pi uptake and mycorrhizal colonization. Moreover, TaPT3-2D-silenced plants exhibited increased susceptibility to biotrophic, hemibiotrophic, and necrotrophic fungi, accompanied by reduced expression of pathogen-related genes. The simultaneous impairment of Pi uptake, AM symbiosis, and defense responses in silenced plants indicates that TaPT3-2D functionally couples these processes. Functional complementation assays in low-Pi medium further revealed that TaPT3-2D partially rescued defective Pi uptake in mutant MB192 yeast, supporting its role as a high-affinity phosphate transporter. Collectively, these results identify TaPT3-2D as both a key regulator of individual pathways and as a molecular link connecting Pi homeostasis, symbiotic signaling, and disease resistance in wheat.

Sugar transporters play important roles in controlling carbohydrate transport and are responsible for mediating the movement of sugars into cells in numerous organisms. In insects, sugar transporters not only play a role in sugar transport but may also act as receptors for virus entry and the accumulation of plant defense compounds. The brown planthopper, Nilaparvata lugens, inflicts damage on rice plants by feeding on their phloem sap, which is rich in sugars. In the present study, we identified 34 sugar transporters in N. lugens, which were classified into three subfamilies based on phylogenetic analysis. The motif numbers varied from seven to eleven, and motifs 2, 3, and 4 were identified in the functional domains of all 34 NlST proteins. Chromosome 1 was found to possess the highest number of NlST genes, harboring 15. The gut, salivary glands, fat body, and ovary were the different tissues enriched with NlST gene expression. The expression levels of NlST2, 3, 4, 7, 20, 27, 28, and 31 were higher in the gut than in the other tissues. When expressed in a Saccharomyces cerevisiae hexose transporter deletion mutant (strain EBY.VW4000), only ApST4 (previously characterized) and NlST4, 28, and 31 were found to transport glucose and fructose, resulting in functional rescue of the yeast mutant. These results provide valuable data for further studies on sugar transporters in N. lugens and lay a foundation for finding potential targets to control N. lugens.

The Bph15 gene, known for its ability to confer resistance to the brown planthopper (BPH; Nilaparvata lugens Stål), has been extensively employed in rice breeding. However, the molecular mechanism by which Bph15 provides resistance against BPH in rice remains poorly understood. In this study, we reported that the transcription factor OsWRKY71 was highly responsive to BPH infestation and exhibited early-induced expression in Bph15-NIL (near-isogenic line) plants, and OsWRKY71 was localized in the nucleus of rice protoplasts. The knockout of OsWRKY71 in the Bph15-NIL background by CRISPR-Cas9 technology resulted in an impaired Bph15-mediated resistance against BPH. Transcriptome analysis revealed that the transcript profiles responsive to BPH differed between the wrky71 mutant and Bph15-NIL, and the knockout of OsWRKY71 altered the expression of defense genes. Subsequent quantitative RT-PCR analysis identified three genes, namely sesquiterpene synthase OsSTPS2, EXO70 family gene OsEXO70J1, and disease resistance gene RGA2, which might participate in BPH resistance conferred by OsWRKY71 in Bph15-NIL plants. Our investigation demonstrated the pivotal involvement of OsWRKY71 in Bph15-mediated resistance and provided new insights into the rice defense mechanisms against BPH.

Plants deploy receptor-like kinases and nucleotide-binding leucine-rich repeat receptors to confer host plant resistance (HPR) to herbivores¹. These gene-for-gene interactions between insects and their hosts have been proposed for more than 50 years². However, the molecular and cellular mechanisms that underlie HPR have been elusive, as the identity and sensing mechanisms of insect avirulence effectors have remained unknown. Here we identify an insect salivary protein perceived by a plant immune receptor. The BPH14-interacting salivary protein (BISP) from the brown planthopper (Nilaparvata lugens Stål) is secreted into rice (Oryza sativa) during feeding. In susceptible plants, BISP targets O. satvia RLCK185 (OsRLCK185; hereafter Os is used to denote O. satvia-related proteins or genes) to suppress basal defences. In resistant plants, the nucleotide-binding leucine-rich repeat receptor BPH14 directly binds BISP to activate HPR. Constitutive activation of Bph14-mediated immunity is detrimental to plant growth and productivity. The fine-tuning of Bph14-mediated HPR is achieved through direct binding of BISP and BPH14 to the selective autophagy cargo receptor OsNBR1, which delivers BISP to OsATG8 for degradation. Autophagy therefore controls BISP levels. In Bph14 plants, autophagy restores cellular homeostasis by downregulating HPR when feeding by brown planthoppers ceases. We identify an insect saliva protein sensed by a plant immune receptor and discover a three-way interaction system that offers opportunities for developing high-yield, insect-resistant crops.

Brown planthopper (BPH, Nilaparvata lugens Stål), is the most destructive phloem-feeding insect pest of rice (Oryza sativa). The BPH-resistance gene BPH15 has been proved to be effective in controlling the pest and widely applied in rice breeding programs. Nevertheless, molecular mechanism of the resistance remain unclear. In this study, we narrowed down the position of BPH15 on chromosome 4 and investigated the transcriptome of BPH15 rice after BPH attacked. We analyzed 13,000 BC2F2 plants of cross between susceptible rice TN1 and the recombinant inbred line RI93 that carrying the BPH15 gene from original resistant donor B5. BPH15 was mapped to a 0.0269 cM region on chromosome 4, which is 210-kb in the reference genome of Nipponbare. Sequencing bacterial artificial chromosome (BAC) clones that span the BPH15 region revealed that the physical size of BPH15 region in resistant rice B5 is 580-kb, much bigger than the corresponding region in the reference genome of Nipponbare. There were 87 predicted genes in the BPH15 region in resistant rice. The expression profiles of predicted genes were analyzed. Four jacalin-related lectin proteins genes and one LRR protein gene were found constitutively expressed in resistant parent and considered the candidate genes of BPH15. The transcriptomes of resistant BPH15 introgression line and the susceptible recipient line were analyzed using high-throughput RNA sequencing. In total, 2,914 differentially expressed genes (DEGs) were identified. BPH-responsive transcript profiles were distinct between resistant and susceptible plants and between the early stage (6 h after infestation, HAI) and late stage (48 HAI). The key defense mechanism was related to jasmonate signaling, ethylene signaling, receptor kinase, MAPK cascades, Ca2+ signaling, PR genes, transcription factors, and protein posttranslational modifications. Our work combined BAC and RNA sequencing to identify candidate genes of BPH15 and revealed the resistance mechanism that it mediated. These results increase our understanding of plant–insect interactions and can be used to protect against this destructive agricultural pest.