Plant Molecular and Cellular Genetics Section, Bose Institute, Kolkata, India.
PLoS One. 2010 Feb 3;5(2):e9030. doi: 10.1371/journal.pone.0009030.
Biotrophic interaction between host and pathogen induces generation of reactive oxygen species that leads to programmed cell death of the host tissue specifically encompassing the site of infection conferring resistance to the host. However, in the present study, biotrophic relationship between Fusarium oxysporum and chickpea provided some novel insights into the classical concepts of defense signaling and disease perception where ROS (reactive oxygen species) generation followed by hypersensitive responses determined the magnitude of susceptibility or resistant potentiality of the host.
METHODOLOGY/PRINCIPAL FINDINGS: Microscopic observations detected wound mediated in planta pathogenic establishment and its gradual progression within the host vascular tissue. cDNA-AFLP showed differential expression of many defense responsive elements. Real time expression profiling also validated the early recognition of the wound inducing pathogen by the host. The interplay between fungus and host activated changes in primary metabolism, which generated defense signals in the form of sugar molecules for combating pathogenic encounter.
CONCLUSIONS/SIGNIFICANCE: The present study showed the limitations of hypersensitive response mediated resistance, especially when foreign encounters involved the food production as well as the translocation machinery of the host. It was also predicted from the obtained results that hypersensitivity and active species generation failed to impart host defense in compatible interaction between chickpea and Fusarium. On the contrary, the defense related gene(s) played a critical role in conferring natural resistance to the resistant host. Thus, this study suggests that natural selection is the decisive factor for selecting and segregating out the suitable type of defense mechanism to be undertaken by the host without disturbing its normal metabolism, which could deviate from the known classical defense mechanisms.
宿主与病原体之间的生物营养相互作用会引发活性氧的产生，导致宿主组织的程序性细胞死亡，具体范围涵盖感染部位，从而赋予宿主抗性。然而，在本研究中，腐霉菌(Fusarium oxysporum)与鹰嘴豆之间的生物营养关系提供了一些关于防御信号和疾病感知的经典概念的新见解，即在活性氧（ROS）产生之后发生超敏反应，决定了宿主易感性或抗性潜力的大小。
方法/主要发现：显微镜观察检测到了伤介导的植物体内病原建立及其在宿主血管组织内的逐渐进展。cDNA-AFLP 显示出许多防御响应元件的差异表达。实时表达谱分析也验证了宿主对诱导伤的病原体的早期识别。真菌和宿主之间的相互作用激活了初级代谢的变化，以糖分子的形式产生防御信号，以抵御病原的侵袭。
结论/意义：本研究表明，超敏反应介导的抗性存在局限性，特别是当外来入侵涉及到宿主的粮食生产和转运机制时。从获得的结果还可以预测，在鹰嘴豆和腐霉菌之间的相容互作中，超敏反应和活性物质的产生未能赋予宿主防御能力。相反，防御相关基因(s)在赋予抗性宿主天然抗性方面发挥了关键作用。因此，本研究表明，自然选择是宿主选择和分离合适防御机制的决定性因素，而不会干扰其正常代谢，这可能偏离已知的经典防御机制。
