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Author: search.filters.author.Oelmüller, RalfHas files: Yes

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    Trichoderma harzianum protects the Arabidopsis salt overly sensitive 1 mutant against salt stress
    (Springer Nature Publishing AG, 2025) Gandhi, Akanksha; Reichelt, Michael; Goyal, Divya; Vadassery, Jyothilakshmi; Oelmüller, Ralf
    Salt stress is one of the major environmental factors that limits crop productivity. To mount an effective response to cope with salt stress, plants rely on the salt overly sensitive (SOS) pathway. The SOS1, SOS2 and SOS3 proteins are crucial for the maintenance of ion homeostasis and the sos1 mutant is hypersensitive to salt stress. Trichoderma harzianum, a beneficial fungus, increases the tolerance of plants to abiotic stresses. We examined the effect of the Trichoderma strain on the performance of the salt overly sensitive (sos1) mutant of Arabidopsis under salt stress. Compared to the isogenic glabra1 (gl1) control seedlings, the fresh weight, chlorophyll fluorescence, photosynthetic pigment content and transcript level of genes involved in ROS scavenging were increased in Trichoderma-inoculated sos1 plants under 150 mM salt stress. Trichoderma also enhanced the accumulation of the osmolytes proline, alanine, as well as the sucrose and glucose in the salt-stressed sos1, but not gl1 mutants, and the accumulation of Na+ was restricted in the sos1 mutant. The beneficial effects of T. harzianum could be attributed to higher colonization rates of the sos1 mutant compared to the gl1 controls. In conclusion, these findings underscore that the Trichoderma strain activates stronger salt protective responses in the salt-sensitive sos1 mutant than in control gl1 plants. Therefore, the Trichoderma strain is a valuable tool to investigate how a beneficial endophyte can stimulate salt tolerance responses in the host to promote its performance under stress.
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    PiHOG1, a stress regulator MAP kinase from the root endophyte fungus Piriformospora indica, confers salinity stress tolerance in rice plants
    (Nature Publishing Group, 2016) Jogawat, Abhimanyu; Vadassery, Jyothilakshmi; Verma, Nidhi; Oelmüller, Ralf; Dua, Meenakshi; Nevo, Eviatar; Johri, Atul Kumar
    In this study, yeast HOG1 homologue from the root endophyte Piriformospora indica (PiHOG1) was isolated and functionally characterized. Functional expression of PiHOG1 in S. cerevisiae ∆hog1 mutant restored osmotolerance under high osmotic stress. Knockdown (KD) transformants of PiHOG1 generated by RNA interference in P. indica showed that genes for the HOG pathway, osmoresponse and salinity tolerance were less stimulated in KD-PiHOG1 compared to the wild-type under salinity stress. Furthermore, KD lines are impaired in the colonization of rice roots under salinity stress of 200 mM NaCl, and the biomass of the host plants, their shoot and root lengths, root number, photosynthetic pigment and proline contents were reduced as compared to rice plants colonized by WT P. indica. Therefore, PiHOG1 is critical for root colonisation, salinity tolerance and the performance of the host plant under salinity stress. Moreover, downregulation of PiHOG1 resulted not only in reduced and delayed phosphorylation of the remaining PiHOG1 protein in colonized salinity-stressed rice roots, but also in the downregulation of the upstream MAP kinase genes PiPBS2 and PiSSK2 involved in salinity tolerance signalling in the fungus. Our data demonstrate that PiHOG1 is not only involved in the salinity response of P. indica, but also helping host plant to overcome salinity stress.