The interaction between the nucleus and the different organelles is important in the physiology of the plant. Reactive oxygen species (ROS) are a by-product of the oxidation of organic molecules to obtain energy by the need to carry out the electron transfer between the different enzymatic complexes. However, they also have a role in the generation of what is known as retrograde signaling. This signal comes from the different organelles in which the oxidation of molecules or the electron transference is taking place such as mitochondria and chloroplasts. Furthermore, ROS can also induce the release of signals from the apoplast. It seems that these signals plays a role communicating to the nucleus the current status of the different parts of the plant cell to induce a changes in gene expression. In this review, the molecular mechanism of ROS retrograde signaling is described.
Reactive oxygen species (ROS) is a group of unstable molecules which shows either different levels of oxygen oxidation states or unpaired electrons which is characteristic of free radicals. Most common ROS include: singlet oxygen (1O2), ozone (O3), hydrogen peroxide (H2O2), superoxide (O2.-), hydroxyl free radical (HO.) and perhydroxyl radical (HOO.), which is the conjugate acid of the superoxide [
These highly chemically reactive molecules are generated by the metabolism of mitochondria [
The present review will describe the outcomes on retrograde signaling from 2005 to date. There are also excellent reviews of the topic done before this time period for interested readers [
There are several signaling phenomena in which ROS plays a role in retrograde signaling [
The retrograde signal phenomenon consists in the generation of ROS in different organelles, which is used as a relay signal to the nucleus to induce a response, although the receptors for these molecules remain unidentified [
In chloroplasts, it appears that H2O2 as well as 1O2 play a role in the retrograde signaling to the nucleus [
Most likely the retrograde signals carry out the control of ABI4 expression at both the transcription and post-translation levels, although this phenomenon is fairly unknown. However, it was found by using treatments to induce retrograde signals, that the transcriptional regulator known as PTM is released from the chloroplast envelop and transported to the nucleus. Moreover, in the nucleus, this regulator induce ABI4 gene expression [
The GUN acronym means genomes uncoupled and this phenomena was studied for first time in mutants of
The molecule methylerythritol cyclodiphosphate (MEcPP) is an isoprenoid precursor which is involved in the response to the
Executer 1 and Executer 2 play a role in the retrograde signal initiated by singlet oxygen generated by chloroplast. The Executers 1 and 2 are required for suppression of the singlet oxygen induced gene expression. This particular ROS is highly unstable and that is why it is unlikely to move from the chloroplast to the nucleus. Because of this, EXECUTER protein plays a role as a second messenger initiated by the singlet oxygen. However, it seems that the primary function of singlet oxygen is not the control of chloroplast performance but the activation of an stress related pathway in response to pathogen attack, wounding and drought stress [
This phenomenon was first described in the communication between organelles within cells [
It has been shown that 1O2 can oxidize the polyunsaturated fatty acids, which leads to the production of 10-hydroxy-8,12,15(E,Z,Z) octadecatrienoic acid and 15-hydroxy-8,12,15(E,Z,Z) octadecatrienoic. Besides, the production of 9-hydroxy-8,12,15(E,Z,Z) octadecatrienoic, 13-hydroxy-8,12,15(E,Z,Z) octadecatrienoic, 12-hydroxy-8,12,15(E,Z,Z) octadecatrienoic, and 16-hydroxy-8,12,15(E,Z,Z) octadecatrienoic, was found to be the result of the oxidation of the polyunsaturated fatty acids by either 1O2 or free radicals [
The apoplast is the region composed of the cell walls between the cells, and it is delimited by the plasma membrane. In the apoplast, the production of H2O2 and 1O2, is carried out by cell wall peroxidases, and NADPH oxidases, also known as respiratory burst oxidase homologs [
It is clear that ROS are not only by-products of molecule oxidation, but rather play an important role in sending messages to the nucleus. This is called retrograde signal, and it plays a role by alerting the nucleus about the physiological status of a particular organelle. The study of these molecules will help in the elucidation of the role that plays the mechanism of the interaction between nucleus and organelles on plant physiology.