During land plant evolution, the number of genes encoding for components of the thiol redox regulatory network and the generator systems of reactive oxygen species (ROS) expanded, tentatively indicating a role in tailored environmental acclimatization. This hypothesis has been validated experimentally and theoretically during the last decades. Recent developments of dynamic roGFP-based in vivo sensors for H₂O₂ and the redox potential of the glutathione pool paved the way for dissecting the kinetics changes in these decisive parameters in response to environmental stressors. The versatile cellular redox sensory and response regulatory system monitors alterations in redox metabolism and controls the activity of redox target proteins, and thereby affects most, if not all, cellular processes ranging from transcription to translation and metabolism. This review exemplarily describes the role of the redox- and ROS-dependent regulatory network in realising the proper response to diverse environmental stresses. The selected case studies concern different environmental challenges, namely excess excitation energy, the heavy metal cadmium and the metalloid arsenic, nitrogen, or phosphate shortage as examples for nutrient deficiency, wounding, and nematode infestation. Each challenge affects the redox regulatory and ROS network, but the present state of knowledge also pinpoints to pressing open questions concerning the translation of redox regulation to environmental acclimatization.

Root-knot nematodes cause global economic losses in a wide range of crops. We investigated the potential of seed coatings of the cover cropPhacelia tanacetifolia(Boraginaceae) when inoculated with the nematophagous fungusPochonia chlamydosporia(Hypocreales: Clavicipitaceae) to protect subsequently grown tomato plants from root galling caused by the root-knot nematodeMeloidogyne hapla(Tylenchida: Meloidogynidae). Therefore, seeds ofP. tanacetifoliawere coated withP. chlamydosporiablastospores and planted inM. hapla-infested pots. After 50 days of growth in infested soil,M. haplaeggs were extracted fromP. tanacetifoliaroots and quantified. Tomato plants grown in the remaining soil served as bioindicator ofM. haplainfestation as expressed by the gall index. Results showed that seed coating ofP. tanacetifoliawithP. chlamydosporia(290 ± 51 CFU per seed) reduced the number ofM. haplaeggs up to 95.6% in comparison to untreated controls.Pochonia chlamydosporiaas blastospore suspension (5·10⁸blastospores per 600 ml soil) reduced the number ofM. haplaeggs by up to 75.5%. Additionally, tomato plants grown for 50 days in substrates previously planted withP. tanacetifoliaseeds coated withP. chlamydosporiashowed a significantly lower gall index than plants grown in untreated pots. In conclusion, biological enhancement ofP. tanacetifoliaby seed coating withP. chlamydosporiasuccessfully reducedM. haplaand thus provides an additional tool in the management of this nematode. The method still has potential for further improvement such as increasing blastospore viability within the seed coating by optimized formulation technology.

Seed treatment is a powerful technique for adding beneficial ingredients to plants during the seed preparation process. Biopolymers as drying agents and delivery systems in seed treatments were investigated for their biocompatibility with blastospores of the nematophagous fungus Pochonia chlamydosporia. To produce a novel seed treatment for the cover crop Phacelia tanacetifolia, xanthan gum TG and gellan gum were the most promising biopolymers in combination with potato starch and bentonite. The seed treatment process as well as the drying process were specially designed to be scalable, which make it suitable for applying the developed seed treatment in agriculture. Application of gellan gum in seed treatments led to 6.3% ± 1.6% of vital blastospores per seed compared to 3.8% ± 0.3% of vital blastospores when applying xanthan gum. Storage tests for seed treatments with 0.5% gellan gum indicated a higher stability at 4 °C compared to storage at 21 °C. After 42 days of storage at 4 °C, 54.1% ± 15.1% of the applied blastospores were viable compared to 0.3% ± 0.8% at 21 °C. This novel seed treatment application with P. chlamydosporia blastospores includes the seed treatment procedure, drying process, and storage tests and can easily be upscaled for application in agriculture.

Summary: With this tribute, we want to highlight Professor Walter Traunspurger’s achievements and contributions to education and research in the fields of nematology and ecology. Walter started to teach in 1998 in the Department of Animal Ecology at Bielefeld University (Germany) and completed his tenure in September 2022, a milestone in his career for which he deserves appreciation, although he is surely going to stay as enthusiastic and busy for many years to come. Over his 30 years of an outstanding academic career, he has supervised 22 Ph.D., 49 M.Sc. and 139 B.Sc. students. He has published over 200 research articles in leading zoological, ecological and ecotoxicological journals. Walter is one of the few living nematologists capable of identifying free-living freshwater nematodes to species level. However, his expertise and research interests are much broader with his biota-inclusive and trans-disciplinary approaches. For his students and colleagues, he has been an inexhaustible source of idealism, knowledge and lively experiences. The book, Ecology of freshwater nematodes, edited by Walter in 2021, provides a good overview of his recent research topics. Here, by summarising and sharing his main scientific accomplishments in this article, we hope that his story will inspire the next generation of nematologists and ecologists to continue his legacy and explore the promising avenues of research that he opened up during his productive scientific career.