Pitino Marco, Armstrong Cheryl M, Cano Liliana M, Duan Yongping
U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of Agriculture Fort Pierce, FL, USA.
Institute of Food and Agricultural Sciences, Department of Plant Pathology, Indian River Research and Education Center, University of Florida Fort Pierce, FL, USA.
Front Plant Sci. 2016 Jul 6;7:982. doi: 10.3389/fpls.2016.00982. eCollection 2016.
Candidatus Liberibacter asiaticus "Las" is a phloem-limited bacterial plant pathogen, and the most prevalent species of Liberibacter associated with citrus huanglongbing (HLB), a devastating disease of citrus worldwide. Although, the complete sequence of the Las genome provides the basis for studying functional genomics of Las and molecular mechanisms of Las-plant interactions, the functional characterization of Las effectors remains a slow process since remains to be cultured. Like other plant pathogens, Las may deliver effector proteins into host cells and modulate a variety of host cellular functions for their infection progression. In this study, we identified 16 putative Las effectors via bioinformatics, and transiently expressed them in Nicotiana benthamiana. Diverse subcellular localization with different shapes and aggregation patterns of the effector candidates were revealed by UV- microscopy after transient expression in leaf tissue. Intriguingly, one of the 16 candidates, Las5315mp (mature protein), was localized in the chloroplast and induced cell death at 3 days post inoculation (dpi) in N. benthamiana. Moreover, Las5315mp induced strong callose deposition in plant cells. This study provides new insights into the localizations and potential roles of these Las effectors in planta.
亚洲韧皮杆菌“Las”是一种局限于韧皮部的细菌性植物病原体，也是与柑橘黄龙病（HLB）相关的最普遍的韧皮杆菌物种，柑橘黄龙病是一种在全球范围内对柑橘具有毁灭性的病害。尽管Las基因组的完整序列为研究Las的功能基因组学和Las与植物相互作用的分子机制提供了基础，但由于Las仍有待培养，其效应子的功能表征仍然是一个缓慢的过程。与其他植物病原体一样，Las可能会将效应蛋白传递到宿主细胞中，并调节多种宿主细胞功能以促进其感染进程。在本研究中，我们通过生物信息学鉴定了16个假定的Las效应子，并在本氏烟草中瞬时表达它们。在叶组织中瞬时表达后，通过紫外显微镜观察揭示了效应子候选物具有不同形状和聚集模式的多样亚细胞定位。有趣的是，16个候选物之一Las5315mp（成熟蛋白）定位于叶绿体，并在接种后3天（dpi）在本氏烟草中诱导细胞死亡。此外，Las5315mp在植物细胞中诱导强烈的胼胝质沉积。本研究为这些Las效应子在植物中的定位和潜在作用提供了新的见解。
