Cell fate maintenance: A new function of the HD-ZIP IV protein, ATML1, together with Very Long Chain Fatty Acids

Maintaining the differentiated cell status is important in maintaining the growth and physiology of the organism. The mechanisms for forming a differentiated cell from stem cells are substantially worked out whereas, the mechanisms for maintaining the differentiated status of cells are rarely studied. Here I will discuss how class IV HD_ZIP protein ATML1 promotes giant cell specification (Meyer et al., 2017) and its maintenance in Arabidopsis sepal epidermis. We identified ATML1 targets using inducible RNA-seq on ATML1 and identified the genes involved in very long chain fatty acid (VLCFA) metabolism are differentially regulated. Mutation in these VLCFA synthesis genes results in reduced giant cell development. To our surprise, we found that inhibition of VLCFA synthesis results in the division of fully differentiated, endoreduplicated giant cells, which we did not think was possible. Furthermore, the daughter of the former giant cell dedifferentiates and can redifferentiate into stomatal cells. Thus, here we were able to uncover the role of HD-ZIPIV in cell maintenance in addition to cell identity specification