AUTHOR=Fu Yang , Yang Yong , Chen Shaoping , Ning Nina , Hu Honghong 

TITLE=Arabidopsis IAR4 Modulates Primary Root Growth Under Salt Stress Through ROS-Mediated Modulation of Auxin Distribution

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00522

DOI=10.3389/fpls.2019.00522

ISSN=1664-462X

ABSTRACT=<p>High salinity is one of the major environmental stresses that plants encounter. Roots are the initial and direct organs to perceive the signal. However, how plant roots perceive and respond to salinity at the molecular and physiological levels is still poorly understood. Here, we report that <italic>IAA-CONJUGATE-RESISTANT 4</italic> (<italic>IAR4</italic>) plays a key role in primary root growth under salt stress conditions. Mutation of <italic>IAR4</italic> led to increased sensitivity to salt stress conditions, with strongly inhibited primary root growth and reduced survival rate in two <italic>iar4</italic> mutant alleles. <italic>iar4</italic> mutants accumulated greater Na<sup>+</sup> and exhibited a greater Na<sup>+</sup>/K<sup>+</sup> ratio under NaCl treatment. In addition, more reactive oxygen species (ROS) accumulated in the <italic>iar4</italic> mutants due to reduced ROS scavenging. NaCl treatment greatly suppressed the expression levels of <italic>ProPIN1:PIN1-GFP</italic>, <italic>ProPIN2:PIN2-GFP</italic>, <italic>ProPIN3:PIN3-GFP</italic>, and <italic>ProDR5:GFP</italic>, and suppressed root meristem activity in <italic>iar4</italic>. GSH or auxin treatment greatly recovered the <italic>PIN</italic> expression, auxin distribution and primary root growth in the <italic>iar4</italic> mutants, suggesting ROS is a vital mediator between salt stress and auxin response. Our data support a model in which IAR4 integrates ROS and auxin pathways to modulate primary root growth under salinity stress conditions, by regulation of PIN-mediated auxin transport.</p>