Identification of three auxin regulated peroxidases involved in root hair cellsize control

ELIANA MARZOL; ESTEVEZ, JOSÉ M.

Congreso; Signat Workshop on Environmental Regulation of Plant Development; 2019

Univerida Catolica de Chile

A root hair is the single-cellular protrusion able to extend in response to external and internal signals.This cell is prepared to increase several hundred-fold its original size, increasing the superficial area of the whole roots exposed to nutrients and water. Although final root hair lenght has vital physiological implications, the molecular mechanisms that control it remain largely unknown. PERs are heme-containing enzymes secreted in the extracellular space where they perform two different enzymatic cycles, namely the peroxidative and hydroxylic cycles. During the peroxidative cycle, the enzyme converts different substrates, including cell wall phenolic compounds and structural proteins, into free radicals that can subsequently combine together to form covalent linkages. This activity contributes to cell wall stiffening and therefore limits growth. PERs can also cause cell wall loosening through the hydroxylic cycle, in which H2O2 and O2− are used to generate hydroxyl radicals, including ?OH, that lead to nonenzymatic cleavage of polysaccharides. PERs can, therefore, play opposite roles in cell expansion, being able to cause both wall stiffening and loosening, depending on the growth conditions. PERs can also generate O2−, which is then dismutated into H2O2, through the oxidation of NAD(P)H. These enzymes can both positively and negatively modulate apoplastic ROS levels. In this study, we propose a molecular mechanism that links the auxin module to activation the transcription factor RSL4, which directly targets genes of PERs, increasing peroxidasa activity. We have identify that PERA, PERB y PERC are essentials in this process.