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Analysis of AGP contribution to the dynamic assembly and mechanical properties of cell wall during pollen tube growth

Leszczuk, Agata, Kozioł, Arkadiusz, Szczuka, Ewa, Zdunek, Artur
Plant science 2019 v.281 pp. 9-18
Fragaria ananassa, arabinogalactan proteins, atomic force microscopy, callose, cell walls, cellulose, fluorescent antibody technique, mechanical properties, modulus of elasticity, pectins, pollen tubes, secretion, structural proteins
Arabinogalactan proteins as cell wall structural proteins are involved in fundamental processes during plant development and growth. The aim of this study was to evaluate AGP function in the distribution of pectin, cellulose and callose along Fragaria x ananassa pollen tube and to associate the cell wall structure with local mechanical properties. We used Yariv reagent which interacts with AGPs and allows the observation of the assembly of cell walls without AGPs performing their function. Cytochemical, immunofluorescence labelling and atomic force microscope have been used to characterize the changes in cell wall structure and stiffness. It was shown that disordering of the structure of AGP present in cell walls affects the localization of cellulose, pectins and the secretion of callose. Changes in cell wall assembly are relevant to pollen tube mechanical properties. The stiffness gradient lengthwise through the axis of the pollen tube has demonstrated a significantly higher Young’s modulus of the shank region than the growth zone. It has been revealed that the apex of the pollen tube cultured in the presence of Yariv reagent is stiffer (1.68 MPa) than the corresponding region of the pollen tube grown under control conditions (0.13-0.27 MPa). AGP affects the structure of the cell wall by changing the distribution of other components and the modification of their localization, and hence it plays a significant role in the mechanical properties of the cell wall.