Myrosin cells. The tissue macrophages of plants?

Plant myrosin cells, similar to tissue macrophages of mammalians appear as distinct cells surrounded by other tissue cells. Both cell types are involved in defense and growth regulation of other cells, and both cell types generate a wide range of products. Plant tissues can contain cells with characteristics, which differ from the surrounding cells in the same tissue. One of these cell types is named myrosin cells, because they contain the enzyme myrosinase (thioglucoside glucohydrolase). Myrosinases with some help from more than 10 different protein factors, Fe2+ and ascorbic acid, degrades thioglucosides and generate a wide range of possible reaction products. These products are believed to be involved in dedfense against insects and phytopathogens. However, the large number of substrates, myrosinases, associated factors and cleavage products reported may indicate that this system has more functions in the plant. In addition to the defense role, a function in sulphur and nitrogen metabolism and a potential role as a supplier of hormone precursors are some of the most probable functions. I will describe our efforts to understand the molecular and cellular organization and function of such specialized cells, their content and role in Arabidopsis, other plants and insects.