DEXH Box RNA Helicase–Mediated Mitochondrial Reactive Oxygen Species Production in Arabidopsis Mediates Crosstalk between Abscisic Acid and Auxin Signaling

Abstract

It is well known that abscisic acid (ABA) promotes reactive oxygen species (ROS) production through plasma membraneassociated NADPH oxidases during ABA signaling. However, whether ROS from organelles can act as second messengers in ABA signaling is largely unknown. Here, we identified an ABA overly sensitive mutant, abo6, in a genetic screen for ABAmediated inhibition of primary root growth. ABO6 encodes a DEXH box RNA helicase that is involved in regulating the splicing of several genes of complex I in mitochondria. The abo6 mutant accumulated more ROS in mitochondria, as established using a mitochondrial superoxide indicator, circularly permuted yellow fluorescent protein. Two dominant-negative mutations in ABA insensitive1 (abi1-1) and abi2-1 greatly reduced ROS production in mitochondria. The ABA sensitivity of abo6 can also be compromised by the atrbohF mutation. ABA-mediated inhibition of seed germination and primary root growth in abo6 was released by the addition of reduced GSH and exogenous auxin to the medium. Expression of auxin-responsive markers ProDR5:GUS (for synthetic auxin response element D1-4 with site-directed mutants in the 59-end from soybean):bglucuronidase) and Indole-3-acetic acid inducible2:GUS was greatly reduced by the abo6 mutation. Hence, our results provide molecular evidence for the interplay between ABA and auxin through the production of ROS from mitochondria. This interplay regulates primary root growth and seed germination in Arabidopsis thaliana.

Abscisic Acid and LATERAL ROOT ORGAN DEFECTIVE/NUMEROUS INFECTIONS AND POLYPHENOLICS Modulate Root Elongation via Reactive Oxygen Species in Medicago truncatula

“…In Arabidopsis and maize, ABA stimulates O 2 .2 and H 2 O 2 production in guard cells, leaves, and roots via NADPH oxidase activity (Guan et al, 2000;Zhang, 2001, 2002;Kwak et al, 2003;He et al, 2012). In contrast, our findings indicate that ABA treatment reduces levels of O 2 .2 in both wild-type and latd roots in M. truncatula (Fig.…”

CYCLIN H;1 Regulates Drought Stress Responses and Blue Light-Induced Stomatal Opening by Inhibiting Reactive Oxygen Species Accumulation in Arabidopsis

“…H 2 O 2 functions as a signal molecule in a wide range of abiotic stress responses, including the expression of antioxidant and defense genes (Karpinski et al, 1999), stomatal closure (Kwak et al, 2003), and the regulation of cell expansion and plant development (Kwak et al, 2003;He et al, 2012). Our results indicate that H 2 O 2 accumulates (Fig.…”

Mitochondrial Energy and Redox Signaling in Plants

“…The identification of ABI4 as a mediator of RTG signaling suggests an intimate linkage between mitochondrial regulation and ABA signaling (64). In addition, crosstalk of mitochondrial ROS with auxin and ABA signaling has also been reported recently (74), further pointing to a central role of mitochondria in orchestrating cellular hormone signaling.…”

“…This cameleon sensor appears technically very promising to open a door to dissect plant mitochondrial calcium signaling. A circularly permuted yellow fluorescent protein sensor reported to respond to mitochondrial superoxide has also been used in plants (74,196). However, this probe has been shown to actually report pH and not superoxide in mitochondria (198,231).…”