Black pepper (Piper nigrum L.) is an important spice crop with high economic value. However, its production is severely hampered by the oomycete pathogen, Phytophthora capsici. Integrative disease management strategies have been developed to control the pathogen, but the pathogen is in the phase of evolving its virulence. Absolute resistance against Phytophthora rot was not reported in black pepper germplasm. However, Piper colubrinum, a wild species is reported as resistant. Resistance proteins are involved in continuous surveillance of pathogen entry and activation of plant defense signalling pathways for an effective hypersensitive response to prevent pathogen invasion. In this study, a sequence-based homology approach using the conserved nucleotide-binding site (NBS) of known plant resistance genes was used to isolate Resistance Gene Analogs (RGA) and assess their transcript level during Phytophthora infection. The RGA transcript level was evaluated in resistant wild species (P. colubrinum), two moderately resistant black pepper genotypes (IISR Sakthi and 04-P24-1), and one susceptible genotype (Subhakara). The identified RGAs of black pepper were found to be of non-TIR R gene class with NBS motifs. The expressions of six PnRGAs were assessed employing qRT-PCR at different time points after challenging with highly aggressive Phytophthora isolate. The kinetics of differential expression post-infection with P. capsici indicates the differential timing and magnitude of pathogen recognition in resistant P. colubrinum and moderately resistant black pepper genotypes compared to susceptible genotype. In silico analysis revealed that differentially expressed P. nigrum RGAs function through ADP phosphorylation, which is a key process in pathogen recognition. The identification of P. nigrum RGAs induced by P. capsici should provide valuable information for cloning and characterization of resistance genes.

中文翻译：

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黑胡椒（Piper nigrum L.）中辣椒疫霉识别相关抗性基因类似物的鉴定

黑胡椒（Piper nigrum L.）是一种重要的香料作物，具有很高的经济价值。然而，它的生产受到卵菌病原体辣椒疫霉的严重阻碍。已经制定了综合疾病管理策略来控制病原体，但病原体正处于发展其毒力的阶段。在黑胡椒种质中没有报道对疫霉腐病的绝对抗性。然而，据报道，Piper colubrinum 是一种野生物种，具有抗药性。抗性蛋白参与病原体进入的持续监测和植物防御信号通路的激活，以产生有效的超敏反应，以防止病原体入侵。在这项研究中，使用已知植物抗性基因的保守核苷酸结合位点 (NBS) 的基于序列的同源性方法用于分离抗性基因类似物 (RGA) 并评估其在疫霉感染期间的转录水平。在抗性野生物种 (P. colubrinum)、两种中等抗性黑胡椒基因型 (IISR Sakthi 和 04-P24-1) 和一种易感基因型 (Subhakara) 中评估 RGA 转录水平。发现已鉴定的黑胡椒 RGA 属于具有 NBS 基序的非 TIR R 基因类别。在用高侵袭性疫霉分离株攻击后，在不同时间点使用 qRT-PCR 评估了六种 PnRGA 的表达。P. capsici 感染后差异表达的动力学表明抗性 P. 病原体识别的不同时间和程度。与易感基因型相比，colubrinum 和中等抗性黑胡椒基因型。计算机分析显示，差异表达的 P. nigrum RGA 通过 ADP 磷酸化起作用，这是病原体识别的关键过程。由 P. capsici 诱导的 P. nigrum RGA 的鉴定应该为抗性基因的克隆和表征提供有价值的信息。