Department of Molecular Biology and Ecology of Plants, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel.
Phytopathology. 2011 Jul;101(7):828-38. doi: 10.1094/PHYTO-09-10-0247.
Certain hypovirulent Rhizoctonia isolates effectively protect plants against well-known important pathogens among Rhizoctonia isolates as well as against other pathogens. The modes of action involved in this protection include resistance induced in plants by colonization with hypovirulent Rhizoctonia isolates. The qualifications of hypovirulent isolates (efficient protection, rapid growth, effective colonization of the plants, and easy application in the field) provide a significant potential for the development of a commercial microbial preparation for application as biological control agents. Understanding of the modes of action involved in protection is important for improving the various aspects of development and application of such preparations. The hypothesis of the present study is that resistance pathways such as systemic acquired resistance (SAR), induced systemic resistance (ISR), and phytoalexins are induced in plants colonized by the protective hypovirulent Rhizoctonia isolates and are involved in the protection of these plants against pathogenic Rhizoctonia. Changes in protection levels of Arabidopsis thaliana mutants defective in defense-related genes (npr1-1, npr1-2, ndr1-1, npr1-2/ndr1-1, cim6, wrky70.1, snc1, and pbs3-1) and colonized with the hypovirulent Rhizoctonia isolates compared with that of the wild type (wt) plants colonized with the same isolates confirmed the involvement of induced resistance in the protection of the plants against pathogenic Rhizoctonia spp., although protection levels of mutants constantly expressing SAR genes (snc1 and cim6) were lower than that of wt plants. Plant colonization by hypovirulent Rhizoctonia isolates induced elevated expression levels of the following genes: PR5 (SAR), PDF1.2, LOX2, LOX1, CORI3 (ISR), and PAD3 (phytoalexin production), which indicated that all of these pathways were induced in the hypovirulent-colonized plants. When SAR or ISR were induced separately in plants after application of the chemical inducers Bion and methyl jasmonate, respectively, only ISR activation resulted in a higher protection level against the pathogen, although the protection was minor. In conclusion, plant colonization with the protective hypovirulent Rhizoctonia isolates significantly induced genes involved in the SAR, ISR, and phytoalexin production pathways. In the studied system, SAR probably did not play a major role in the mode of protection against pathogenic Rhizoctonia spp.; however, it may play a more significant role in protection against other pathogens.
某些弱毒立枯丝核菌分离物有效地保护植物免受立枯丝核菌分离物中众所周知的重要病原体以及其他病原体的侵害。这种保护所涉及的作用模式包括通过弱毒立枯丝核菌分离物的定殖诱导植物产生抗性。弱毒分离物的资格（有效保护、快速生长、有效定殖植物和易于在田间应用）为开发作为生物防治剂应用的商业微生物制剂提供了巨大的潜力。了解保护所涉及的作用模式对于改进此类制剂的开发和应用的各个方面都很重要。本研究的假设是，受保护的弱毒立枯丝核菌分离物定殖的植物中会诱导系统获得抗性 (SAR)、诱导系统抗性 (ISR) 和植保素等抗性途径，并参与这些植物对致病性立枯丝核菌的保护。与用相同分离物定殖的野生型 (wt) 植物相比，防御相关基因 (npr1-1、npr1-2、ndr1-1、npr1-2/ndr1-1、cim6、wrky70.1、snc1 和 pbs3-1) 缺陷的拟南芥突变体的保护水平的变化证实了诱导抗性在保护植物免受致病性立枯丝核菌属的侵害中的作用，尽管持续表达 SAR 基因的突变体的保护水平 (snc1 和 cim6) 低于 wt 植物。弱毒立枯丝核菌分离物对植物的定殖诱导以下基因的表达水平升高：PR5（SAR）、PDF1.2、LOX2、LOX1、CORI3（ISR）和 PAD3（植保素产生），这表明这些途径都在弱毒定殖植物中被诱导。在用化学诱导剂 Bion 和茉莉酸甲酯分别单独诱导植物中的 SAR 或 ISR 后，只有 ISR 激活导致对病原体的更高保护水平，尽管保护作用较小。总之，用保护性弱毒立枯丝核菌分离物对植物进行定殖可显著诱导参与 SAR、ISR 和植保素产生途径的基因。在研究系统中，SAR 可能在对抗致病性立枯丝核菌属的保护模式中不起主要作用；然而，它可能在对抗其他病原体的保护中发挥更重要的作用。
