中国柑橘黄龙病病原菌两个原噬菌体超变异基因遗传多样性

【目的】通过原噬菌体区域高度变异的基因位点研究柑橘黄龙病病原菌亚洲种（‘Candidatus Liberibacter asiaticus’）的种群分化，探讨病原菌种群遗传多样性水平和遗传结构。【方法】基于2种原噬菌体类型（SC1和SC2）对应的超变异基因区域设计2对引物（Lap-TJ-F/Lap-TJ-R1和Lap-TJ-F/Lap-TJ-R2），对中国不同柑橘产区的224个‘Ca. L. asiaticus’株系进行PCR检测和序列分析。【结果】PCR扩增的条带类型呈多态性，具有4种条带类型（SC1-1、SC1-2、SC2-1和SC2-2），西南地区以SC1-1型为主，广东、广西地区以SC2-1型为主，福建、江西、浙江地区没有明显优势的扩增型。分析SC1-1和SC1-2对应序列表明，其差异系由于132 bp的卫星序列和24 bp的小卫星序列2种串联重复序列数不同引起，而SC2-1和SC2-2的差异系由原噬菌体内部基因重排引起。【结论】中国不同地理来源病原菌株系在原噬菌体区域具有较丰富的多态性，对该基因区域研究将有助于揭示中国‘Ca. L. asiaticus’种群的遗传多样性。

Genetic Diversity of Two Hypervariable Genes from Prophage Regions of ‘Candidatus Liberibacter asiaticus’ in China

【Objective】 Hypervariable genomic loci of prophage region were used to study population differentiation and genetic diversity of ‘Candidatus Liberibacter asiaticus’, the putative casual agent of citrus Huanglongbing (HLB). 【Method】 Two primer sets (Lap-TJ-F/Lap-TJ-R1 and Lap-TJ-F/Lap-TJ-R2), targeted hypervariable genomic regions of two prophage types (SC1 and SC2), respectively, were used for PCR detection and sequence analysis of 224 ‘Ca. L. asiaticus’ strains from different citrus producing areas in China. 【Result】 PCR amplicon polymorphisms and four amplion types (SC1-1, SC1-2, SC2-1 and SC2-2) were observed, SC1-1 and SC2-1 were the predominant types in Southwestern region and Guangdong-Guangxi region, respectively, and no dominant types were found in Fujian-Jiangxi-Zhejiang region. The sequence differences in SC1-1/SC1-2 were mainly caused by different combinations of two kinds of tandem repeats with 132 bp satellite sequence and 32 bp mini-satellite sequence, respectively. The diversity in SC2-1/SC2-2 likely derived from prophage gene rearrangement. 【Conclusion】Significant diversity in the prophage regions was investigated from ‘Ca. L. asiaticus’ strains collected from different geographical origins. Further studies on these genomic regions would be helpful for deciphering the genetic diversity of ‘Ca. L. asiaticus’ populations in China.