Asif Muhammad, Hu Renjian, Xie Ting, Fan Rong, Long Youhua, Wang Yong, Wu Shiping, Zhao Zhibo, Huang Lili
Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang, China.
Research Center for Engineering Technology of Kiwifruit, Institute of Crop Protection, College of Agriculture, Guizhou University, Guiyang, China.
Virulence. 2025 Dec;16(1):2543983. doi: 10.1080/21505594.2025.2543983. Epub 2025 Aug 22.
pv. (Psa) is the causal agent of kiwifruit bacterial canker, but the factors affecting its pathogenicity in natural settings remain poorly explored. In this study, we isolated two Psa strains, G126 and G282, from infected kiwifruit orchards in Guizhou Province of China. Both isolates, categorized as Psa-biovar 3, were confirmed through Psa3-specific primers and phylogenomic analysis. Pathogenicity assays on kiwifruit cultivar "Hongyang" leaves and branches showed significantly reduced numbers of necrotic spots and reduced lesion sizes upon infection with G282 compared to the G1 positive control strain, while G126 showed a nonpathogenic phenotype. Additionally, both strains failed to induce a hypersensitive response in nonhost plants and exhibited significantly reduced promoter activity of the , , and genes, which are crucial for the type III secretion system (T3SS). Genomic sequencing revealed that the T3SS of G126 was defective due to a single-nucleotide polymorphism in the gene, while G282 was entirely deficient in the type VI secretion system (T6SS), which potentially regulates the expression of T3SS genes. Transcriptomic analysis showed widespread alterations in key aspects of the secretion system, protein transport, and signal transduction, further supporting the phenotype characteristics exhibited by the strains. This study enhances our understanding of the genetic basis of nonpathogenic and partially pathogenic Psa isolates, highlighting the functional interdependencies between T3SS and T6SS.
丁香假单胞菌猕猴桃致病变种（Psa）是猕猴桃细菌性溃疡病的致病因子，但在自然环境中影响其致病性的因素仍未得到充分研究。在本研究中，我们从中国贵州省受感染的猕猴桃果园中分离出两株Psa菌株，G126和G282。通过Psa3特异性引物和系统基因组分析，证实这两株分离株均属于Psa生物变种3。对猕猴桃品种“红阳”的叶片和枝条进行致病性测定，结果显示，与G1阳性对照菌株相比，用G282感染后坏死斑数量显著减少，病斑大小减小，而G126表现出无致病表型。此外，这两株菌株均未能在非寄主植物中诱导过敏反应，并且III型分泌系统（T3SS）关键的hpaA、hrcC和hrpZ基因的启动子活性显著降低。基因组测序显示，G126的T3SS因hpaA基因中的单核苷酸多态性而存在缺陷，而G282完全缺乏VI型分泌系统（T6SS），T6SS可能调节T3SS基因的表达。转录组分析表明，分泌系统、蛋白质运输和信号转导的关键方面存在广泛变化，进一步支持了这些菌株表现出的表型特征。本研究增进了我们对非致病性和部分致病性Psa分离株遗传基础的理解，突出了T3SS和T6SS之间的功能相互依赖性。
