Putrescine Depletion Affects Arabidopsis Root Meristem Size by Modulating Auxin and Cytokinin Signaling and ROS Accumulation

Polyamines (PAs) dramatically affect root architecture and development, mainly by unknown mechanisms; however, accumulating evidence points to hormone signaling reactive oxygen species (ROS) as candidate mechanisms. To test this hypothesis, PA levels were modified progressively reducing ADC1/2 activity Put levels, then changes in meristematic zone (MZ) size, ROS, auxin cytokinin (CK) investigated. Decreasing putrescine resulted an interesting inverted-U-trend primary growth a similar trend MZ differential (Put), spermidine (Spd), combined spermine (Spm) plus thermospermine (Tspm) levels. At low concentrations, ROS accumulation increased coincidently with decreasing treatment scavenger KI partially rescued phenotype. Analysis of double AtrbohD/F loss-of-function mutants indicated that NADPH oxidases not involved H2O2 elevated due back-conversion, terminal catabolism, scavenging, or another pathway. non-linear signaling, whereas CK decreased, re-balancing signaling. Different modulated the expression PIN1 PIN2 transporters, indicating distribution. These data strongly suggest PAs modulate size through both Arabidopsis.