Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, Consejo Nacional de Investigaciones Científicas y técnicas (CONICET), Saladillo 2468, C1440FFX, Buenos Aires, Argentina.
Appl Microbiol Biotechnol. 2010 Jun;87(2):467-77. doi: 10.1007/s00253-010-2631-2. Epub 2010 May 7.
In this review, we summarise the current knowledge on three pathogens that exhibit distinct tissue specificity and modes of pathogenesis in citrus plants. Xanthomonas axonopodis pv. citri causes canker disease and invades the host leaf mesophyll tissue through natural openings and can also survive as an epiphyte. Xylella fastidiosa and Candidatus Liberibacter are vectored by insects and proliferate in the vascular system of the host, either in the phloem (Candidatus Liberibacter) or xylem (X. fastidiosa) causing variegated chlorosis and huanglongbing diseases, respectively. Candidatus Liberibacter can be found within host cells and is thus unique as an intracellular phytopathogenic bacterium. Genome sequence comparisons have identified groups of species-specific genes that may be associated with the particular lifestyle, mode of transmission or symptoms produced by each phytopathogen. In addition, components that are conserved amongst bacteria may have diverse regulatory actions underpinning the different bacterial lifestyles; one example is the divergent role of the Rpf/DSF cell-cell signalling system in X. citri and X. fastidiosa. Biofilm plays a key role in epiphytic fitness and canker development in X. citri and in the symptoms produced by X. fastidiosa. Bacterial aggregation may be associated with vascular occlusion of the xylem vessels and symptomatology of variegated chlorosis.
在这篇综述中，我们总结了三种在柑橘植物中表现出明显组织特异性和发病机制模式的病原体的现有知识。黄单胞菌柑橘亚种引起溃疡病，通过自然开口侵入宿主叶肉组织，也可以作为附生菌存活。丁香假单胞菌和韧皮部杆菌通过昆虫传播，并在宿主的维管束系统中增殖，分别在韧皮部（韧皮部杆菌）或木质部（丁香假单胞菌）引起斑驳黄化和黄龙病。韧皮部杆菌可以在宿主细胞内发现，因此是一种独特的细胞内植物病原菌。基因组序列比较已经确定了一组与每种植物病原菌特定生活方式、传播模式或产生的症状相关的种特异性基因。此外，在细菌中保守的成分可能对不同的细菌生活方式具有不同的调节作用；例如，Rpf/DSF 细胞间信号系统在柑橘溃疡病菌和丁香假单胞菌中的作用不同。生物膜在柑橘溃疡病菌的附生适应性和溃疡病的发展以及丁香假单胞菌引起的症状中起着关键作用。细菌聚集可能与木质部导管的血管阻塞和斑驳黄化的症状有关。
