Regulation of auxin response by UBIQUITIN-SPECIFIC PROTEASE14/ TARANI in Arabidopsis thaliana

Abstract

The genetic pathway regulating auxin response in Arabidopsis is well established and provides us a framework to assess whether TNI belongs to this pathway. The total number of lateral roots is taken as a read-out of auxin response to interpret the genetic interaction data. Genetic interaction studies of tni with known mutants with defects in lateral root formation revealed that the reduced lateral-root phenotype of tni is enhanced when the function of the auxin signaling molecules such as ARF7, TIR1 and AUX1 was compromised. These genetic interaction data suggest that TNI acts parallel to ARF7, TIR1 and AUX1 in regulating auxin response. However, it should be noted that tni is a hypomorphic allele, making the interpretation of the genetic interaction data rather difficult. Together with the Aux/IAA stabilization data, we conclude that TNI acts in the auxin signaling pathway involving TIR1, ARF7 and AUX1 to regulate auxin-related development in Arabidopsis. Our study unravels a novel function of UBP14/ TNI in the auxin-response pathway by regulating the turn-over of Aux/IAA repressors through maintaining cellular ubiquitin pool in Arabidopsis thaliana