Functional traits of hydrolytic enzymes and visualized enzymatic activity in the rhizosphere gradients of Zea mays L.

Alive plants and soil microorganisms are the influential sources of extracellular enzymes facilitating decomposition of polymeric organic compounds. Enzyme activities are especially intensive and spatially heterogeneous in the rhizosphere, where microorganisms are stimulated by rhizodeposition. Two-dimensional activity distribution of hydrolytic enzymes participating in transformation of soil organics in the distance gradients from the root can be visualized under UV light by zymography - by placing a fluorogenic substrate-saturated membrane on the soil surface. Functional traits of enzymes can be co-localized with spatial distribution of enzymatic activity by precise micro-sampling based on zymography. We used rhizobox experiment to visualize activity of β-glucosidase, leucine aminopeptidase, and phosphatase in the rhizosphere of wild type and root hairless mutant of Zea mays L. cultivated for 3 weeks. After precise micro-sampling, we determined kinetic parameters of enzymes: max potential activity and affinity to substrate in the rhizosphere gradients. Finally, we compared the correspondence of enzymatic activity determined by zymography and by kinetic approach. This work was conducted within the framework of the priority program 2089, funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project number: 403664478. Seeds of the maize were provided by Caroline Marcon and Frank Hochholdinger (University of Bonn).

Keywords: zymography, enzyme kinetic, maize, rhizosphere gradients