Combined nitrogen and drought stress leads to overlapping and unique proteomic responses in potato

Main conclusion: Nitrogen deficient and drought-tolerant or sensitive potatoes differ in proteomic responses under combined (NWD) and individual stresses. The sensitive genotype ‘Kiebitz’ exhibits a higher abundance of proteases under NWD. Abstract: Abiotic stresses such as N deficiency and drought affect the yield of Solanum tuberosum L. tremendously. Therefore, it is of importance to improve potato genotypes in terms of stress tolerance. In this study, we identified differentially abundant proteins (DAPs) in four starch potato genotypes under N deficiency (ND), drought stress (WD), or combined stress (NWD) in two rain-out shelter experiments. The gel-free LC–MS analysis generated a set of 1177 identified and quantified proteins. The incidence of common DAPs in tolerant and sensitive genotypes under NWD indicates general responses to this stress combination. Most of these proteins were part of the amino acid metabolism (13.9%). Three isoforms of S-adenosyl methionine synthase (SAMS) were found to be lower abundant in all genotypes. As SAMS were found upon application of single stresses as well, these proteins appear to be part of the general stress response in potato. Interestingly, the sensitive genotype ‘Kiebitz’ showed a higher abundance of three proteases (subtilase, carboxypeptidase, subtilase family protein) and a lower abundance of a protease inhibitor (stigma expressed protein) under NWD stress compared to control plants. The comparably tolerant genotype ‘Tomba’, however, displayed lower abundances of proteases. This indicates a better coping strategy for the tolerant genotype and a quicker reaction to WD when previously stressed with ND

Analysis of genotypic differences in biochemical and physiological adjustments to N-deficiency and drought stress in potatoes (Solanum tuberosum L.) with consideration of yield components

Ziel dieser Arbeit war die Phänotypisierung von Kartoffelsorten unter N-Mangel und Trockenstress auf morphologischer, physiologischer und biochemischer Ebene. Dazu wurden in einem Gefäßversuch 17 europäische Kartoffelsorten in zwei N-Stufen und zwei Bewässerungsstrategien in einem rain-out-shelter zweijährig geprüft. Mittels eines in-vitro-Screenings sollten sortenabhängige Reaktionen auf N-Mangel erfasst werden. Exemplarisch wurden an zwei unterschiedlich reagierenden Sorten proteomische Untersuchungen zur Identifizierung von auf N-Mangel reagierenden Proteinen durchgeführt. In Bezug auf Knollen- und Stärkeertrag zeigte sich die Sorte ‘Tomba‘ sowohl unter N-Mangel als auch unter Trockenstress tolerant, während ‘Kiebitz‘ mit Ertragseinbußen reagierte. Andere Sorten zeigten je nach Stressart unterschiedliche Reaktionen. Die Stickstoffnutzungseffizienz war unter N-Mangel erhöht. Die Wassernutzungseffizienz verringerte sich unter Trockenstress und war bei ausreichender N-Versorgung stets höher als unter N-Mangel. Biochemische und physiologische Merkmale der Blätter wurden zu zwei Zeitpunkten während der Trockenstressphase analysiert. Der Prolingehalt nahm unter Trockenstress zu, wobei sich eine ausreichende N-Versorgung auf die Dynamik und Höhe auswirkte. Der Gesamtgehalt an löslichem Zucker stieg unter kurz anhaltendem Trockenstress und fiel bei längerer Dauer wieder ab. Das Wasserpotential im Blatt nahm bei Trockenstress schnell ab. Ausgeprägte osmotische Anpassungen waren aber nicht nachzuweisen. Korrelationen zwischen biochemischen und physiologischen Parametern zu Ertragsmerkmalen waren zu schwach, um als Toleranzmarker verwendet zu werden. Sortenunterschiede waren auch unter in vitro Bedingungen signifikant. Spezifische Unter-schiede unter N-Mangel zeigten sich insbesondere in der Biomasseproduktion, im Chlorophyll-gehalt und in der N-Metabolisierung. Interessante Reaktionen wurden hinsichtlich des Wurzel-Spross Verhältnisses festgestellt, welches von einigen Sorten unter N-Mangel gesteigert wurde. 21 % der mittels Proteomanalyse detektierten Proteine unterschieden sich in ihrer Abundanz zwischen dem ausgewählten sensitiven und dem toleranten Genotyp. Im Vergleich zwischen Kontrolle und N-Mangel waren dies 19,5 % beim toleranten und 15 % beim sensitiven Genotyp. Die wenigen in beiden Sorten durch N-Mangel gleichermaßen betroffenen Proteine betrafen allgemeine Stressreaktionen. Sortenspezifisch unter N-Mangel reguliert waren insbesondere Enzyme des Kohlenhydratmetabolismus und der Chlorophyllsynthese. Speziell die Rubisco activase zeigte interessante Modifikationen zwischen den Genotypen und N-Stufen. Diese Dissertation wurde nur als Druckausgabe veröffentlicht.This work aimed at comprehensive phenotyping of starch potato cultivars in response to N-deficiency and drought stress at the morphological, physiological and biochemical level. For this purpose, 17 European potato cultivars were investigated in two years pot trials in a rain-out shelter with two N-levels and two water supply regimes. Additionally, a broad in vitro screening was performed to monitor specific traits under different N-levels in dependence of the genotype. Furthermore, out of these two contrasting genotypes were analysed in a proteomic approach to identify proteins associated with genotype specific responses to N-deficiency. With regard to tuber and starch yield cv. Tomba proved to be comparatively tolerant and cv. Kiebitz rather sensitive under both, N-deficiency and drought stress. Other cultivars responded differentially depending on the type of stress. Nitrogen use efficiency generally increased under N-deficiency. Water use efficiency decreased under limited water supply, but was increased by increased N-supply. Biochemical and physiological parameters of leaves were analysed at two time points during a drought stress phase. The proline content increased under drought, while the N-supply level had an effect on the speed and extent of its accumulation. The content of total soluble sugars increased at short-term drought and dropped back at long-term drought, which was more pronounced at higher N-supply. The leaf water potential decreased rapidly under drought, however, significant osmotic adjustment was not detected. Correlations of biochemical or physiological parameters to agronomic traits were too weak to serve as markers for abiotic stress tolerance. In vitro assays disclosed significant differences between cultivars in the ability to maintain biomass production, photosynthesis and N-metabolization under decreased N-supply. Furthermore, genotype dependent responses were detected regarding the root to shoot ratio, which was increased under N-deficiency in some specific cultivars. The proteomic analysis revealed that 21 % of the detected proteins differed in abundance between the sensitive and the tolerant genotype. In control and N-deficiency conditions 19.5 % were differentially accumulated in the sensitive and 15 % in the tolerant genotype. Out of a total of 106 differentially abundant proteins, only eight were detected in both genotypes, which were mainly associated with general stress response. In the tolerant genotype, the determined high chlorophyll content was associated with an increase of respective catabolic enzymes. In particular, rubisco activaseshowed interesting modulations in dependence of genotypes and N-levels. This dissertation was only published as a printed edition

Combined nitrogen and drought stress leads to overlapping and unique proteomic responses in potato

MAIN CONCLUSION: Nitrogen deficient and drought-tolerant or sensitive potatoes differ in proteomic responses under combined (NWD) and individual stresses. The sensitive genotype 'Kiebitz' exhibits a higher abundance of proteases under NWD. ABSTRACT: Abiotic stresses such as N deficiency and drought affect the yield of Solanum tuberosum L. tremendously. Therefore, it is of importance to improve potato genotypes in terms of stress tolerance. In this study, we identified differentially abundant proteins (DAPs) in four starch potato genotypes under N deficiency (ND), drought stress (WD), or combined stress (NWD) in two rain-out shelter experiments. The gel-free LC-MS analysis generated a set of 1177 identified and quantified proteins. The incidence of common DAPs in tolerant and sensitive genotypes under NWD indicates general responses to this stress combination. Most of these proteins were part of the amino acid metabolism (13.9%). Three isoforms of S-adenosyl methionine synthase (SAMS) were found to be lower abundant in all genotypes. As SAMS were found upon application of single stresses as well, these proteins appear to be part of the general stress response in potato. Interestingly, the sensitive genotype 'Kiebitz' showed a higher abundance of three proteases (subtilase, carboxypeptidase, subtilase family protein) and a lower abundance of a protease inhibitor (stigma expressed protein) under NWD stress compared to control plants. The comparably tolerant genotype 'Tomba', however, displayed lower abundances of proteases. This indicates a better coping strategy for the tolerant genotype and a quicker reaction to WD when previously stressed with ND

The pre-exposure SARS-CoV-2-specific T cell repertoire determines the quality of the immune response to vaccination

SARS-CoV-2 infection and vaccination generates enormous host-response heterogeneity and an age -dependent loss of immune-response quality. How the pre-exposure T cell repertoire contributes to this heterogeneity is poorly understood. We combined analysis of SARS-CoV-2-specific CD4+ T cells pre-and post-vaccination with longitudinal T cell receptor tracking. We identified strong pre-exposure T cell variability that correlated with subsequent immune-response quality and age. High-quality responses, defined by strong expansion of high-avidity spike-specific T cells, high interleukin-21 production, and specific immuno-globulin G, depended on an intact naive repertoire and exclusion of pre-existing memory T cells. In the elderly, T cell expansion from both compartments was severely compromised. Our results reveal that an intrinsic defect of the CD4+ T cell repertoire causes the age-dependent decline of immune-response quality against SARS-CoV-2 and highlight the need for alternative strategies to induce high-quality T cell responses against newly arising pathogens in the elderly