A KNOX â ¡ transcription factor suppresses the NLR immune receptor BRG8-mediated immunity in rice.

Nucleotide-binding site and leucine-rich repeat (NLR) proteins are activated by detecting pathogen effectors, which in turn trigger host defenses and cell death. Although many NLRs have been identified, the mechanism responsible for NLR-triggered defense responses are still poorly understood. In this study, through GWAS approach, we identified a novel NLR gene, Blast Resistance Gene 8 (BRG8), conferring resistance to rice blast and bacterial blight diseases. Consistently, the BRG8 overexpression and complementation lines exhibited enhanced resistance to both pathogens. Subcellular localization assays showed that BRG8 localized in both cytoplasm and nucleus. More evidence revealed that nuclear-localized BRG8 enhanced rice immunity without hypersensitive response (HR)-like phenotype. Furthermore, we also demonstrated the CC domain of BRG8 not only physically interacted with itself, but also interacted with the KNOX Ⅱ protein HOMEOBOX ORYZA SATIVA59 (HOS59). Knockout of HOS59 in BRG8 background showed enhanced resistance to M. oryzae strain CH171 and Xoo strain CR4, similar to BRG8 background. In contrast, overexpression of HOS59 in BRG8 background, compromised the HR-like phenotype and resistance response. Further analysis revealed that HOS59 promotes the degradation of BRG8 via the 26S proteasome pathway. Collectively, our study highlights HOS59 as NLR immune regulators, fine-tune BRG8-mediated immune responses against pathogens, and provides new insights into NLR association and function in plant immunity.

[Relationship between Mutations of the Epidermal Growth Factor Receptor Gene and Drug-Resistance to Gefitinib in Human Lung Cancer in vitro.].

BACKGROUND: To explore cell lines' difference of drug-resistance to gefitinib and the underlying mechanism. METHODS: Human lung cancer cell lines of PC9, PC9/AB2, PC9/AB11, PC9/BB4 were treated in vitro, exons 18-21 of EGFR gene were sequenced and EGFR gene mRNA levels were measured. RESULTS: Four cell lines' drug resistance difference of gefitinib were validated. All the four cell lines had the 15 bp deletion at exon 19, and AB11 had A to G point-mutation at exon 20. PC9 EGFR gene in the sensitive cell line was expressed much higher than that in 3 resistance cell lines by real-time PCR. CONCLUSIONS: There is significant difference of drug-resistance to gefitinib existed among the lung cancer cell lines PC9, PC9/AB2, PC9/AB11 and PC9/BB4. The mutations changes of expressive level of EGFR gene might be correlated with the acquired drug-resistance to gefitinib in lung cancer cell lines.