The functions of WHIRLY1 and REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 in cross tolerance responses in plants: a hypothesis

Abstract

Chloroplasts are important sensors of environment change, fulfilling key roles in the regulation of plant growth and development in relation to environmental cues. Photosynthesis produces a repertoire of reductive and oxidative (redox) signals that provide information to the nucleus facilitating appropriate acclimation to a changing light environment. Redox signals are also recognized by the cellular innate immune system allowing activation of non-specific, stress-responsive pathways that underpin cross tolerance to biotic–abiotic stresses. While these pathways have been intensively studied in recent years, little is known about the different components that mediate chloroplast-to-nucleus signalling and facilitate cross tolerance phenomena. Here, we consider the properties of the WHIRLY family of proteins and the REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 (RRTF1) in relation to chloroplast redox signals that facilitate the synergistic co-activation of gene expression pathways and confer cross tolerance to abiotic and biotic stresses. We propose a new hypothesis for the role of WHIRLY1 as a redox sensor in chloroplast-to-nucleus retrograde signalling leading to cross tolerance, including acclimation and immunity responses. By virtue of its association with chloroplast nucleoids and with nuclear DNA, WHIRLY1 is an attractive candidate coordinator of the expression of photosynthetic genes in the nucleus and chloroplasts. We propose that the redox state of the photosynthetic electron transport chain triggers the movement of WHIRLY1 from the chloroplasts to the nucleus, and draw parallels with the regulation of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1).

Geomagnetic Field (Gmf) and Plant Evolution: Investigating the Effects of Gmf Reversal on <em>Arabidopsis thaliana </em>Development and Gene Expression

“…RRTF1 transcription factor facilitates the synergistic co-activation of gene expression of these pathways 15,31 , and can be potentially involved in oxidative stress 32 . Therefore, upregulation of RRTF1 is expected when oxygen scavenging is reduced.…”

“…To test the hypothesis, we therefore built a triaxial octagonal Helmholtz coil-pairs magnetic field compensation system (triaxial coils), which is able to accurately reverse the normal GMF conditions. We used Arabidopsis thaliana as a model plant and we tested the effect of reversed GMF on gene expression of some important genes: CRUCIFERIN 3 (CRU3), that encodes a 12S seed storage protein that is tyrosine-phosphorylated and its phosphorylation state is modulated in response to ABA in Arabidopsis thaliana seeds 12,13 ; the Copper Transport Protein1 (COTP1), that encodes a heavy metal transport/ detoxification superfamily protein with the predominant function in soil Cu acquisition and pollen development 14 ; and Redox Responsive Transcription Factor1 (RRTF1), that encodes a member of the ERF (ethylene response factor) subfamily B-3 of ERF/AP2 transcription factor family that contains one AP2 domain that facilitate the synergistic co-activation of gene expression pathways and confer cross tolerance to abiotic and biotic stresses 15 . .…”

Living to Die and Dying to Live: The Survival Strategy behind Leaf Senescence

“…Furthermore, WHIRLY1 (WHY1), a protein implicated in plant defense, acts as a negative regulator of WRKY53 expression (Miao et al, 2013). Interestingly, WHY1 was recently proposed to be a redox sensor that moves from the chloroplasts to the nucleus (Foyer et al, 2014). In addition, both WHY1 and WRKY53 are downstream components of SA signaling pathways that act independently of NPR1 (Desveaux et al, 2004;Miao and Zentgraf, 2007).…”

Redox- and Reactive Oxygen Species-Dependent Signaling into and out of the Photosynthesizing Chloroplast

“…General or specific permeabilization of the envelope for the release of regulatory proteins from the chloroplast, which depends on, for instance, the ROS and redox state, might be a potent mechanism involved in the conditional release of WHIRLY1 from the chloroplast to the cytosol and the subsequent regulation of target genes such as PR1 and PR2 (Isemer et al, 2012;Foyer et al, 2014). Another example is the envelope-tethered PHD-type transcription factor with transmembrane domain (PTM), which is released from the plastid surface upon treatment of leaves with the plastid translation inhibitor lincomycin, the carotenoid biosynthesis inhibitor norflurazon, or high light and controls the expression of ABI4 by binding to its promoter (Sun et al, 2011).…”