Study of the role of Phytolongins in root development: a targeted knock out approach in Arabidopsis thaliana (L.) Heynh.

Among non-SNARE longin proteins, phytolongins represent a subgroup found exclusively in land plants. In Arabidopsis thaliana, four phytolongin isoforms have been identified (PHYL1.1, PHYL1.2, PHYL2.1 and PHYL2.2), all encoded by monoexonic genes. Previous studies have investigated their expression patterns during plant development and in different tissues, as well as their subcellular localization, showing their presence in membrane-associated compartments. These findings suggest that phytolongins may be involved in membrane trafficking processes, with a possible role during root development. This hypothesis is supported by the phenotype of phyl2.1 knock-out mutants, which show alterations in seed germination, primary root growth, root zonation, and cell plate organization in the differentiation zone. However, the biological functions of phytolongins are still not completely understood. This thesis project aims to further investigate the role of this protein family by generating root apical meristem (RAM)-specific single knock-out lines for each of the four phytolongin genes and characterizing them through phenotypic and molecular analyses. The study of these mutants will help clarify the specific contribution of each phytolongin to root development. In addition, comparative bioinformatic analyses will be performed to investigate the phylogeny and evolutionary history of these proteins, focusing on their origin and distribution across different organisms. Overall, this work aims to provide new insights into the functional role of phytolongins and their evolutionary significance in plants.