State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China.
BMC Genomics. 2022 Sep 26;23(1):671. doi: 10.1186/s12864-022-08900-2.
Xanthomonas is a genus of gram-negative bacterium containing more than 35 species. Among these pathogenic species, Xanthomonas albilineans (Xal) is of global interest, responsible for leaf scald disease in sugarcane. Another notable Xanthomonas species is Xanthomonas sachari (Xsa), a sugarcane-associated agent of chlorotic streak disease.
The virulence of 24 Xanthomonas strains was evaluated by disease index (DI) and Area Under Disease Progress Curve (AUDPC) in the susceptible inoculated plants (GT 46) and clustered into three groups of five highly potent, seven mild virulent, and twelve weak virulent strains. The highly potent strain (X. albilineans, Xal JG43) and its weak virulent related strain (X. sacchari, Xsa DD13) were sequenced, assembled, and annotated in the circular genomes. The genomic size of JG43 was smaller than that of DD13. Both strains (JG43 and DD13) lacked a Type III secretory system (T3SS) and T6SS. However, JG43 possessed Salmonella pathogenicity island-1 (SPI-1). More pathogen-host interaction (PHI) genes and virulent factors in 17 genomic islands (GIs) were detected in JG43, among which six were related to pathogenicity. Albicidin and a two-component system associated with virulence were also detected in JG43. Furthermore, 23 Xanthomonas strains were sequenced and classified into three categories based on Single Nucleotide Polymorphism (SNP) mutation loci and pathogenicity, using JG43 as a reference genome. Transitions were dominant SNP mutations, while structural variation (SV) is frequent intrachromosomal rearrangement (ITX). Two essential genes (rpfC/rpfG) of the two-component system and another gene related to SNP were mutated to understand their virulence effect. The mutation of rpfG resulted in a decrease in pathogenicity.
These findings revealed virulence of 24 Xanthomonas strains and variations by 23 Xanthomonas strains. We sequenced, assembled, and annotated the circular genomes of Xal JG43 and Xsa DD13, identifying diversity detected by pathogenic factors and systems. Furthermore, complete genomic sequences and sequenced data will provide a theoretical basis for identifying pathogenic factors responsible for sugarcane leaf scald disease.
黄单胞菌是革兰氏阴性细菌属，包含超过 35 个种。在这些致病种中，黄单胞菌白化（Xal）引起的甘蔗叶枯病引起了全球关注。另一个值得注意的黄单胞菌种是黄单胞菌甘蔗（Xsa），它是引起甘蔗黄条病的病原体。
通过接种易感植物（GT46）的病情指数（DI）和病情进展曲线下面积（AUDPC）评估了 24 株黄单胞菌菌株的毒力，并聚类为 5 株高毒力、7 株中等毒力和 12 株弱毒力菌株的 3 个组。高毒力菌株（黄单胞菌白化，XalJG43）及其弱毒相关菌株（黄单胞菌甘蔗，XsaDD13）被测序、组装并注释在圆形基因组中。JG43 的基因组大小小于 DD13。两个菌株（JG43 和 DD13）均缺乏 III 型分泌系统（T3SS）和 T6SS。然而，JG43 拥有沙门氏菌致病性岛-1（SPI-1）。在 JG43 中检测到 17 个基因组岛（GI）中的更多病原体-宿主相互作用（PHI）基因和毒力因子，其中 6 个与致病性有关。在 JG43 中还检测到了 albicidin 和与毒力相关的双组分系统。此外，使用 JG43 作为参考基因组，根据单核苷酸多态性（SNP）突变位点和致病性对 23 株黄单胞菌进行测序和分类，分为三类。转换是 SNP 突变的主要类型，而结构变异（SV）是频繁的染色体内重排（ITX）。双组分系统的两个必需基因（rpfC/rpfG）和另一个与 SNP 相关的基因发生突变，以了解它们的毒力效应。rpfG 的突变导致毒力降低。
这些发现揭示了 24 株黄单胞菌菌株的毒力和 23 株黄单胞菌菌株的变异。我们对 XalJG43 和 XsaDD13 的圆形基因组进行了测序、组装和注释，确定了由致病因子和系统检测到的多样性。此外，完整的基因组序列和测序数据将为鉴定引起甘蔗叶枯病的致病因子提供理论依据。
