Publikationen - Molekulare Signalverarbeitung

Salinity is a constraint limiting plant growth and productivity of crops throughout the world. Understanding the mechanism underlying plant response to salinity provides new insights into the improvement of salt tolerance-crops of importance. In the present study, we report on the responses of twenty cultivars of tomato. We have clustered genotypes into scale classes according to their response to increased NaCl levels. Three local tomato genotypes, representative of different saline scale classes, were selected for further investigation. During early (0 h, 6 h and 12 h) and later (7 days) stages of the response to salt treatment, ion concentrations (Na + , K +  and Ca 2+ ), proline content, enzyme activities (catalase, ascorbate peroxidase and guiacol peroxidase) were recorded. qPCR analysis of candidate genes WRKY (8, 31and 39), ERF (9, 16 and 80), LeNHX (1, 3 and 4) and HKT (class I) were performed. A high K + , Ca 2 + and proline accumulation as well as a decrease of Na +  concentration-mediated salt tolerance. Concomitant with a pattern of high-antioxidant enzyme activities, tolerant genotypes also displayed differential patterns of gene expression during the response to salt stress.

The enzymatic conversion of one chromogenic substrate, -glutamine-p-nitroanilide, and two fluorogenic substrates, -glutaminyl-2-naphthylamide and -glutaminyl-4-methylcoumarinylamide, into their respective pyroglutamic acid derivatives by glutaminyl cyclase (QC) was estimated by introducing a new coupled assay using pyroglutamyl aminopeptidase as the auxiliary enzyme. For the purified papaya QC, the kinetic parameters were found to be in the range of those previously reported for other glutaminyl peptides, such as Gln-Gln, Gln-Ala, or Gln-tert-butyl ester. The assay can be performed in the presence of ammonia up to a concentration of 50 mM. Increasing ionic strength, e.g., potassium chloride up to 300 mM, resulted in an increase in enzymatic activity of about 20%. This is the first report of a fast, continuous, and reliable determination of QC activity, even in the presence of ammonium ions, during the course of protein purification and enzymatic analysis.

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