Dear Colleagues,
Although light is the energy source of life on earth, excessive light can lead to a decline in photosynthetic efficiency. In the light reactions of photosynthesis, reactive oxygen species (ROS), such as superoxide anion radical (O2•–), hydrogen peroxide (H2O2), and singlet oxygen (1O2), are constantly created at basal levels. Under optimal growth conditions, ROS are kept in homeostasis by the antioxidative enzymatic and non-enzymatic systems, but under abiotic or biotic stress conditions, the balance between the creation and elimination of ROS is disrupted. During environmental stress conditions, when the absorbed light energy cannot be used totally for photochemistry, the photosynthetic apparatus is overexcited and the energy is transferred from chlorophyll to oxygen, resulting in surplus ROS accumulation, triggering oxidative stress. This can harm the chloroplast, by producing membrane injuries, protein degradation and enzyme inactivation, that damage the cellular components. Under excess light conditions, the over-excitation of photosystem II (PSII) increases the probability of triplet excited chlorophyll state (3Chl*) formation, from the singlet excited chlorophyll state (1Chl*), through intersystem crossing, producing 1O2. Electron leakage to O2 at photosystem I (PSI) results in O2•–, that is shorter lived than H2O2, which is converted via a disproportionation reaction catalyzed by superoxide dismutase (SOD).
To prevent ROS formation and photoinhibition, the absorbed light energy by the light-harvesting complexes must match the rate of electron transport from PSII to PSI. Among the two photosystems, PSII is particularly vulnerable to photoinhibition, but damage to PSII can be prevented by dissipation of excess light energy as heat, a process known as non-photochemical quenching (NPQ), and typically estimated by chlorophyll fluorescence analysis. In addition to the NPQ mechanism that is considered as the principal photoprotective mechanism, plants have efficient enzymatic and non-enzymatic antioxidant mechanisms.
Although ROS were originally thought to be toxic by-products that must be removed to prevent the oxidative damage to the cell, subsequent studies revealed that ROS are used by most organisms as key signal transduction molecules. Recently, it was discovered that a basal level of ROS is actually required to employ its beneficial function and support life. ROS activate the plant’s defense mechanisms in order to cope with the oxidative stress and are essential as signaling molecules for the regulation of a variety of physiological functions including plant function and development.
In this Special Issue we encourage original research submissions, as well as review/mini review articles, concerning basic aspects and future research directions in this field.
Prof. Michael Moustakas
Guest Editor
Manuscripts should be submitted via our online editorial system at https://imr.propub.com by registering and logging in to this website. Once you are registered, click here to start your submission. Manuscripts can be submitted now or up until the deadline. All papers will go through peer-review process. Accepted papers will be published in the journal (as soon as accepted) and meanwhile listed together on the special issue website. Research articles, reviews as well as short communications are preferred. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office to announce on this website.
Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts will be thoroughly refereed through a double-blind peer-review process. Please visit the Instruction for Authors page before submitting a manuscript. The Article Processing Charge (APC) in this open access journal is 2500 USD. Submitted manuscripts should be well formatted in good English.