AtrbohD and AtrbohF positively regulate abscisic acid-inhibited primary root growth by affecting Ca2+ signalling and auxin response of roots in Arabidopsis

Abstract

Reactive oxygen species (ROS) originating from the NADPH oxidases AtrbohD and AtrbohF play an important role in abscisic acid (ABA)-inhibited primary root growth in Arabidopsis. However, the mechanisms underlying this process remain elusive. In this study, the double mutant atrbohD1/F1 and atrbohD2/F2, in which both AtrbohD and AtrbohF were disrupted, were less sensitive to ABA suppression of root cell elongation than wild-type (WT) plants. Furthermore, the double mutants showed impaired ABA responses in roots, including ROS generation, cytosolic Ca(2+) increases, and activation of plasma membrane Ca(2+)-permeable channels compared with WT. Exogenous H2O2 can activate the Ca(2+) currents in roots of atrbohD1/F1. In addition, exogenous application of the auxin transport inhibitor naphthylphthalamic acid effectively promoted ABA inhibition of root growth of the mutants relative to that of WT. The ABA-induced decreases in auxin sensitivity of the root tips were more pronounced in WT than in atrbohD1/F1. These findings suggest that both AtrbohD and AtrbohF are essential for ABA-promoted ROS production in roots. ROS activate Ca(2+) signalling and reduce auxin sensitivity of roots, thus positively regulating ABA-inhibited primary root growth in Arabidopsis.

ASCORBATE PEROXIDASE6 Protects Arabidopsis Desiccating and Germinating Seeds from Stress and Mediates Cross Talk between Reactive Oxygen Species, Abscisic Acid, and Auxin

“…In addition, two recent studies revealed cross talk between auxin homeostasis and ROS in seed germination and primary root growth (He et al, 2012;Jiao et al, 2013). Whether ABI4 participates in the regulation of auxin homeostasis in seeds remains to be determined.…”

New cross talk between ROS, ABA and auxin controlling seed maturation and germination unraveled in APX6 deficient Arabidopsis seeds

“…In contrast, reduced ability to generate ROS in Arabidopsis mutant deficient in 2 major respiratory burst oxidase homologs rbohD/F, decreased sensitivity to ABA-mediated auxin response in roots. 18 In striking contrast to apx6, abi4 maintained close to 100% germination under all conditions, indicating that this mutant is also insensitive to auxin and resistant to its combination with ABA (Fig. 1).…”

ROS Homeostasis Regulates Somatic Embryogenesis via the Regulation of Auxin Signaling in Cotton

“…Chen et al (30) revealed that AtAPX6 mediates the crosstalk between ROS, ABA, and auxin to protect desiccating and germinating Arabidopsis seeds from stress. Studies on the rbohD and rbohF double mutant have shown the involvement of ROS in activating Ca 2+ signaling and decreasing auxin sensitivity in Arabidopsis roots (32). The disruption of the NADP-linked thioredoxin and glutathione systems in a triple mutant elevated ROS levels and perturbed auxin transport and metabolism (33).…”