Prof. Dr. Jose Estevez

Head of Laboratory
Molecular Basis for Plant Development - Leloir Institute

Host: Jürgen Kleine-Vehn

Tip-growing root hairs are excellent model systems to decipher the molecular mechanism
underlying reactive oxygen species (ROS)-mediated cell elongation. Root hairs are able to
expand in response to external signals, increasing several hundred-fold their original size,
which is important for survival of the plant. Although their final cell size is of fundamental
importance, the molecular mechanisms that control it remain largely unknown. Root hair
polar growth is endogenously controlled by auxin and sustained by oscillating levels of
reactive oxygen species (ROS). Here, we show that ROS production is controlled by the
transcription factors RSL4, which in turn is transcriptionally regulated by auxin through
several Auxin Responsive Factors (ARFs). In this manner, auxin controls ROS-mediated polar
growth by activating RSL4, which then upregulates the expression of genes encoding NADPH
oxidases (also known as RBOHs, RESPIRATORY BURST OXIDASE HOMOLOG proteins) and
Class-III Peroxidases (PER), which catalyse ROS production. Chemical or genetic interference
with the ROS balance or peroxidase activity affect root hair final cell size. Overall, our
findings establish a molecular link between auxin regulated ARFs-RSL4 and ROS-mediated
polar root hair growth.