How does auxin influence on plant developmental responses during salinity?

Abstract

Plants integrate intrinsic developmental programs and quickly adjust growth to environmental stimuli. Plant growth and development largely depend on the phytohormone auxin which exerts its function throughout partially redundant F-box receptors, TIR1-AFBs. Several studies using pharmacological and genetic approaches demonstrated that auxin response is down-regulated under salinity. However, how auxin regulation impacts on growth and developmental programs is still under study. Developmental plasticity of roots is modulated by auxin and also is critical for tolerance to stress. Reasonably, plant acclimation to salinity could involve root growth reprogramming depending on the intensity of the stress whereby plant growth is redirected to diminish stress exposure. It is hypothesized that stress-induced morphological responses (SIMR) are mediated by auxin-mediated redox metabolism. However, one emerging question is how salinity transduces stress signals to regulate root plasticity during plant acclimation. The entwined mechanisms involving miRNAs and Salt Overly Sensitive (SOS) pathway in the regulation of auxin homeostasis will be also discussed.