miR393 regulation of auxin signaling and redox-related components during acclimation to salinity in Arabidopsis

IGLESIAS, MARÍA JOSÉ; TERRILE, MARÍA CECILIA; WINDELS, DAVID; LOMBARDO, CRISTINA; BARTOLI, CARLOS GUILLERMO; VAZQUEZ, FRANCK; ESTELLE, MARK; CASALONGUÉ, CLAUDIA ANAHÍ

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2014

1932-6203

One of the most striking aspects of plant plasticity is the modulation of development inresponse to environmental changes. Plant growth and development largely depend on thephytohormone auxin that exerts its function through a partially redundant family of F-boxreceptors, the TIR1-AFBs. We have previously reported that the Arabidopsis doublemutant tir1 afb2 is more tolerant to salt stress than wild-type plants and we hypothesizedthat down-regulation of auxin signaling might be part of Arabidopsis acclimation to salinity.In this work, we show that NaCl-mediated salt stress induces miR393 expression byenhancing the transcription of AtMIR393A and leads to a concomitant reduction in thelevels of the TIR1 and AFB2 receptors. Consequently, NaCl triggers stabilization ofAux/IAA repressors leading to down-regulation of auxin signaling. Further, we report thatmiR393 is likely involved in repression of lateral root (LR) initiation, emergence andelongation during salinity, since the mir393ab mutant shows reduced inhibition ofemergent and mature LR number and length upon NaCl-treatment. Additionally, mir393abmutant plants have increased levels of reactive oxygen species (ROS) in LRs, andreduced ascorbate peroxidase (APX) enzymatic activity compared with wild-type plantsduring salinity. Thus, miR393 regulation of the TIR1 and AFB2 receptors could be a criticalcheckpoint between auxin signaling and specfic redox-associated components in order tocoordinate tissue and time-specific growth responses and tolerance during acclimation tosalinity in Arabidopsis.