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The brown planthopper, Nilaparvata lugens, is a pest that threatens rice (Oryza sativa) production worldwide. While feeding on rice plants, planthoppers secrete saliva, which plays crucial roles in nutrient ingestion and modulating plant defense responses, although the specific functions of salivary proteins remain largely unknown. We identified an N. lugens-secreted mucin-like protein (NlMLP) by transcriptome and proteome analyses and characterized its function, both in brown planthopper and in plants. NlMLP is highly expressed in salivary glands and is secreted into rice during feeding. Inhibition of NlMLP expression in planthoppers disturbs the formation of salivary sheaths, thereby reducing their performance. In plants, NlMLP induces cell death, the expression of defense-related genes, and callose deposition. These defense responses are related to Ca²⁺ mobilization and the MEK2 MAP kinase and jasmonic acid signaling pathways. The active region of NlMLP that elicits plant responses is located in its carboxyl terminus. Our work provides a detailed characterization of a salivary protein from a piercing-sucking insect other than aphids. Our finding that the protein functions in plant immune responses offers new insights into the mechanism underlying interactions between plants and herbivorous insects.

The brown planthopper (BPH) and white-backed planthopper (WBPH) are the most destructive insect pests of rice, and they pose serious threats to rice production throughout Asia. Thus, there are urgent needs to identify resistance-conferring genes and to breed planthopper-resistant rice varieties. Here we report the map-based cloning and functional analysis of Bph6 , a gene that confers resistance to planthoppers in rice. Bph6 encodes a previously uncharacterized protein that localizes to exocysts and interacts with the exocyst subunit OsEXO70E1. Bph6 expression increases exocytosis and participates in cell wall maintenance and reinforcement. A coordinated cytokinin, salicylic acid and jasmonic acid signaling pathway is activated in Bph6 -carrying plants, which display broad resistance to all tested BPH biotypes and to WBPH without sacrificing yield, as these plants were found to maintain a high level of performance in a field that was heavily infested with BPH. Our results suggest that a superior resistance gene that evolved long ago in a region where planthoppers are found year round could be very valuable for controlling agricultural insect pests. The study reports map-based cloning and functional analysis of Bph6 , which is associated with resistance to planthoppers in rice. BPH6 localizes to the exocyst and interacts with OsEXO70E1, and suppression of OsExo70E1 expression decreases resistance in Bph6 -NIL plants.

BROWN PLANTHOPPER RESISTANCE14 (BPH14), the first planthopper resistance gene isolated via map-based cloning in rice (Oryza sativa), encodes a coiled-coil, nucleotide binding site, leucine-rich repeat (CC-NB-LRR) protein. Several planthopper and aphid resistance genes encoding proteins with similar structures have recently been identified. Here, we analyzed the functions of the domains of BPH14 to identify molecular mechanisms underpinning BPH14-mediated planthopper resistance. The CC or NB domains alone or in combination (CC-NB [CN]) conferred a similar level of brown planthopper resistance to that of full-length (FL) BPH14. Both domains activated the salicylic acid signaling pathway and defense gene expression. In rice protoplasts and Nicotiana benthamiana leaves, these domains increased reactive oxygen species levels without triggering cell death. Additionally, the resistance domains and FL BPH14 protein formed homocomplexes that interacted with transcription factors WRKY46 and WRKY72. In rice protoplasts, the expression of FL BPH14 or its CC, NB, and CN domains increased the accumulation of WRKY46 and WRKY72 as well as WRKY46- and WRKY72-dependent transactivation activity. WRKY46 and WRKY72 bind to the promoters of the receptor-like cytoplasmic kinase gene RLCK281 and the callose synthase gene LOC_Os01g67364.1, whose transactivation activity is dependent on WRKY46 or WRKY72. These findings shed light on this important insect resistance mechanism.

The brown planthopper, Nilaparvata lugens (Stål, 1854), is the most devastating pest of rice (Oryza sativa L.). Although insecticides are used to control this pest, host plant resistance is a more effective and economic solution. Therefore, identification of N. lugens-resistant genes and elucidation of their underlying resistance mechanisms are critical for developing elite rice cultivars with enhanced and durable resistance. Research has shown that in the long-term evolutionary arms race, rice has developed complex defense systems against N. lugens, while N. lugens has developed diverse and sophisticated strategies to overcome the plant’s defenses. This review emphasizes recent advances in the molecular interactions between rice and the N. lugens, particularly focusing on the resistance mechanisms of 17 cloned major N. lugens resistance genes, which have significantly improved our understanding of the molecular basis of rice–N. lugens interactions. We also highlight the roles of several N. lugens salivary components in activating or suppressing rice defense responses. These insights provide a foundation for developing sustainable and effective strategies to manage this devastating pest of rice.

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.

Metal tolerance protein (MTP) family members, functioning as plant divalent cation transporters, play essential roles in maintaining heavy metal homeostasis and tolerance. This study presents a novel comprehensive genomic characterisation of the MTP gene family in Coptis chinensis , involving systematic identification and functional annotation. A total of 25 CcMTP genes were identified and classified into three major subfamilies based on phylogenetic analysis. Conserved motif profiling and gene structure annotation revealed both conserved and divergent features among the subfamilies. Genomic collinearity analysis identified one tandemly duplicated gene pair ( CcMTP12 / CcMTP20 ) in C. chinensis . The promoter regions of CcMTP genes were enriched with cis-acting elements associated with phytohormones, light, and growth and development. Gene expression analysis showed that several CcMTPs were significantly upregulated in response to cadmium stress across different tissues. CcMTP11, CcMTP16 , and CcMTP24 , which exhibited high expression in roots, stems, and leaves, conferred enhanced tolerance to multiple heavy metals. Notably, CcMTP24 promoted Δ ycf1 yeast growth under Cd, iron, zinc, and manganese stress and reduced Cd accumulation in yeast. Collectively, pivotal CcMTPs , such as CcMTP24 identified in this study, may provide mechanistic insights to elucidate the roles of MTPs in heavy metal tolerance in C. chinensis .

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.

It has been reported that the receptor-like cytoplasmic kinases (RLCKs) regulate many biological processes in plants, but only a few members have been functionally characterized. Here, we isolated a rice gene encoding homology protein kinase, , which belongs to the RLCK VI subfamily. transcript accumulated in many tissues at low to moderate levels and at high levels in leaves. Overexpression of (OE- ) caused adaxial rolling and erect morphology of rice leaves. In the rolled leaves of OE- plants, both the number and the size of the bulliform cells are decreased compared to the wild-type (WT) plants. Moreover, the height, tiller number, and seed setting rate were reduced in OE- plants. In addition, the brown planthopper (BPH), a devastating pest of rice, preferred to settle on WT plants than on the OE- plants in a two-host choice test, indicating that OE- conferred an antixenosis resistance to BPH. The analysis of transcriptome sequencing demonstrated that several receptor kinases and transcription factors were differentially expressed in OE- plants and WT plants. These results indicated that may play multiple roles in the development and defense of rice, which may facilitate the breeding of novel rice varieties.

Plants deploy receptor-like kinases and nucleotide-binding leucine-rich repeat receptors to confer host plant resistance (HPR) to herbivores 1 . These gene-for-gene interactions between insects and their hosts have been proposed for more than 50 years 2 . 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 ( Os RLCK185; 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 Os NBR1, which delivers BISP to Os ATG8 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. Insect salivary protein (BISP) targets Os RLCK185 to suppress defence in susceptible plants, whereas in resistant plants BISP binds BPH14 to activate host plant resistance. To restore cellular homeostasis, the resistance mechanism is fine-tuned by selective autophagy.

Brown planthopper (BPH), Nilaparvata lugens Stål, is one of the most devastating insect pests of rice (Oryza sativa L.). Currently, 30 BPH-resistance genes have been genetically defined, most of which are clustered on specific chromosome regions. Here, we describe molecular cloning and characterization of a BPH-resistance gene, BPH9, mapped on the long arm of rice chromosome 12 (12L). BPH9 encodes a rare type of nucleotide-binding and leucine-rich repeat (NLR)-containing protein that localizes to the endomembrane system and causes a cell death phenotype. BPH9 activates salicylic acid- and jasmonic acid-signaling pathways in rice plants and confers both antixenosis and antibiosis to BPH. We further demonstrated that the eight BPH-resistance genes that are clustered on chromosome 12L, including the widely used BPH1, are allelic with each other. To honor the priority in the literature, we thus designated this locus as BPH1/9. These eight genes can be classified into four allelotypes, BPH1/9-1, -2, -7, and -9. These allelotypes confer varying levels of resistance to different biotypes of BPH. The coding region of BPH1/9 shows a high level of diversity in rice germplasm. Homologous fragments of the nucleotide-binding (NB) and leucine-rich repeat (LRR) domains exist, which might have served as a repository for generating allele diversity. Our findings reveal a rice plant strategy for modifying the genetic information to gain the upper hand in the struggle against insect herbivores. Further exploration of natural allelic variation and artificial shuffling within this gene may allow breeding to be tailored to control emerging biotypes of BPH.