Callose Metabolism in Flax Fibers During Gravity Response: Analysis of Gene Expression

Motor responses of plants related to tropisms are usually carried out using elongation growth mechanisms. However, this study examined gravitropism at the level of cells (primary phloem fibers) that have completed their growth and are forming a thickened tertiary cell wall. A stocktaking and analysis of the gene expression of enzymes for callose metabolism was carried out at different stages of development of phloem fibers of flax (Linum usitatissimum L.) and during the gravitational response. Genes of putative beta-1,3-glucan synthases (GSLs) and beta-1,3-glucanases (BGs) were identified, which have a differential expression pattern in the studied cells, among which genes with the maximum level of expression at a certain stage of development were noted. Generally, the expression of beta-1,3-glucan synthase genes was decreased during gravitropism, while beta-1,3-glucanase genes were characterized by different expression profiles, among which genes with an increased expression level (LusBG1 and LusBG3) were identified only during the graviresponse. The data obtained allowed the authors to assume the presence of active callose metabolism in the cell wall of the studied fibers at different stages of development and that callose degradation dominates during the gravitational response in such fibers. The results of the work lay the foundation for further studies of the function of callose in the development of fibers and the implementation of the motor response of plants.