Immunohistochemical Localization of Proteins in the Phloem: Problems and Solutions

The technique of immunolocalization in differentiated phloem cells is a challenging task given their specific functions, anatomy, and cell organellar infrastructure. Incorporation of specific cell wall components in thickened cell walls of phloem cells is often the source of unspecific labeling and erroneous localization data. Furthermore, tissue preservation of cells that are exposed to high osmotic pressure is a very challenging task, encountering many pitfalls. Therefore, special care is required regarding the generation and purification of specific antibodies and in the protocols used for tissue preservation. Here, some useful tips for cautious tissue preparation and antibody purification for immunolocalization are given. In parallel, the main focus should be on the confirmation of immunohistochemical localization data by alternative methods, promoter reporter gene studies, or activity tests.Keywords Phloem transport, Carbon allocation, Sucrose transporter, Phloem proteins, Immunolocalization, Subcellular localization.