Semi-automatic quantification of 3D Histone H3 phosphorylation signals during cell division in Arabidopsis root meristems

O_LIPosttranslational modification of histones during the cell cycle is a major process controlling many aspects of cell division. Among the variety of histone modifications, mitotic phosphorylation of histone H3 at serine 10 (H3S10ph) plays a crucial role, particularly in proper chromosome segregation. Here we aimed at precisely quantifying this phosphorylation dynamics during mitosis in plant cells, in order to reveal molecular pathways involved in this process. C_LIO_LIWe describe an analysis pipeline based on 3D image analysis that allows to semi-automatically quantify H3S10 phosphorylation in mitotic Arabidopsis root cells. We also developed a new method for the compensation of signal attenuation in Z, based on measurement of objects of interest themselves. C_LIO_LIWe show that this new attenuation correction method allows significant gains in accuracy and statistical power. Using this pipeline, we were able to reveal small H3S10ph differences between cells treated with hesperadin, an inhibitor of an H3S10ph kinase, or between Arabidopsis mutants affected in PP2A phosphatase activity. C_LIO_LIThis tool opens new avenues to explore such regulation pathway in plants, using the wealth of genetic material available in Arabidopsis. It can also be applied to study other histone post-translational modifications, and more generally to any discrete 3D signals. C_LI