We can run and hide in the shade if the sunlight gets too intense, but sessile plants have no choice but to deal with it in place. Excess light absorption by the photosynthetic apparatus can generate more reduction potential than downstream biosynthetic reactions can utilize. This results in production of reactive oxygen species (ROS) such as free radicals, H2O2, and superoxide anion, which damage cellular components including membranes, DNA, and proteins (Waszczak et al., 2018). Because solar energy both provides reducing power for biosynthesis and creates harmful ROS, plants have developed several photoprotective mechanisms that can protect the photosynthetic machinery and detoxify the ROS using electrons from reduced glutathione (GSH). Nonphotochemical quenching (NPQ) increases tolerance to high light and protects Photosystem II (PSII) by dissipating excess solar energy as heat. It is lacking in the Arabidopsis npq1 mutant, which has significantly reduced PSII activity. Cyclic electron flow (CEF) is an electron sink that is regulated by PROTON GRADIENT REGULATION 5 (PGR5), and this protects Photosystem I (PSI) from oxidative damage by excess light. In high light, Arabidopsis pgr5 mutants are stunted and show severe damage to PSI. Despite the physiological importance of photosynthesisderived ROS, it has been difficult to determine the dynamics of their daily production due to the destructive nature of most biochemical approaches for ROS or GSH detection. In recent years, redox-sensitive versions of green fluorescent protein (roGFPs) have been developed as probes to monitor the redox status of cellular tissues in vivo (Nietzel, 2019). These probes are highly sensitive to redox changes, reversible, and pH-insensitive. Reduction of roGFPs is specifically mediated by glutaredoxins, which receive electrons from the GSH pool. Therefore, changes in roGFP fluorescence reflect modulation of the redox state of downstream targets of these glutaredoxins. To test whether ROS scavenging by the GSH pool plays a role in sensing and responding to light stress, Haber et al. (2021) have recently employed a chloroplast-targeted redox sensor, chl-roGFP2. They used it to continuously monitor diurnal changes in the stromal GSH reduction potential (EGSH) caused by high light or fluctuating light conditions. Because the fluorescence intensity of oxidized versus reduced chlroGFP2 in the chloroplast stroma varies when excited at 405 nm versus 465 nm, the 405/465 ratio is a reliable indication of the degree of its oxidation in whole-plant assays (see Figure). They measured the recovery from oxidation by H2O2 under different light intensities and found that the 405/465 ratio dropped immediately after H2O2 treatment independent of the concentration used, and it dropped more quickly under higher light. There was no probe oxidation following pretreatment with DCMU, which blocks electron flow in PSII, demonstrating that chl-roGFP2 oxidation directly depends on and responds to photosynthetic activity. To allow continuous monitoring of redox dynamics under varying light conditions, the researchers developed an automated assay using Arabidopsis plants grown in 12-well microplates. At the dark-to-light transition, they noticed an immediate peak of oxidation, demonstrating light-induced oxidant production. Surprisingly, there was a similar peak at the light-to-dark transition. Following a shift from low to high light, they saw immediate oxidation and a subsequent gradual reduction accompanied by a reduction in PSII activity. Further experiments using npq1 and pgr5 mutants, which are deficient in NPQ and CEF, respectively, showed that In B ri ef

When seeds germinate underground, the emerging seedlings must push upward through the soil to reach sunlight and begin photoautotrophic growth. As the hypocotyl emerges from the seed, mechanical pressure against the soil induces the production of ethylene, which accumulates and promotes hypocotyl

MYB proteins are a group of transcription factors that are highly conserved in all vertebrates and were first implicated in avian myeloblastosis (leukemia). Subsequently, they were shown to be cellular proto-oncogenes that regulate production of blood cells in animals. MYB proteins contain a DNA

Precise trafficking of proteins to their proper destinations in the cell, whether to an organelle, a membrane, or the cytoplasm, is required for optimal cellular function. Because most plastid proteins are nucleus-encoded and translated in the cytoplasm, proper targeting and import relies on the

It’s not just human relationships that may require a chaperone to prevent inappropriate interactions. Numerous proteins in organisms from Escherichia coli to us, especially hydrophobic membrane proteins, also require chaperones in aqueous environments to prevent inappropriate interactions such as

Symbiotic associations with microorganisms are widespread among both woody and herbaceous plant species, including most agronomic crops ([Brundrett and Tedersoo, 2018][1]). Mycorrhizal fungi provide their hosts with mineral nutrients absorbed from the soil in exchange for fixed carbon compounds

Plant cell growth is often limited by the availability of two key nutrients, phosphorus (P) and nitrogen (N). As in mammals and yeast, a kinase known as TOR (target of rapamycin) is a key nutrient-responsive regulator of primary metabolism and cell growth in plants ([Gonzalez and Hall, 2017][1]; [

Carotenoid pigments not only produce the vibrant yellows and oranges of flowers, fruits, and autumn leaves but also are important in both plant and human health. They act both as accessory pigments in photosynthetic light harvesting and as photoprotectants that absorb excess energy during

The ATP synthase complex of chloroplasts is an elegant example of the union of structure and function at the molecular level ([Junge and Nelson, 2015][1]). This enzyme complex consists of an integral membrane CFo component that transports protons plus an extrinsic CF1 component that synthesizes ATP

The phytohormone abscisic acid (ABA) regulates a variety of processes in plants, including seed dormancy, seedling growth, and response to environmental stresses. A fascinating study by [Ni et al. (2019)][1] shows that ABA responses in rice ( Oryza sativa ) are regulated by an interaction between

Fungal pathogens such as Botrytis cinerea can cause devastating losses to agricultural crops—ask any strawberry, grape, or tomato grower. To prevent these losses, plants can summon a variety of immune responses by recognizing specific molecules associated with pathogen attack and/or internal

Cyclins and cyclin-dependent protein kinases (CDKs) are critical regulators of cell cycle progression. Although CDK1 is essential for mitosis in animals and fungi, CDKA, the plant and algal ortholog of CDK1, is not essential for cell division in Arabidopsis thaliana ([Nowack et al., 2012][1]). By

Autophagy, or “self eating,” is the process cells use to consume unwanted intracellular structures such as damaged organelles, excess membranes, and unneeded proteins ([Mizushima and Komatsu, 2011][1]). Typically, the unwanted structure becomes surrounded by an autophagosomal membrane, which

What do photosynthesis, neonatal jaundice, and a next-generation solar cell have in common? All involve tetrapyrroles, complex molecules with four linked pyrrole rings, each ring containing one nitrogen and four carbon atoms. Tetrapyrroles exist in either cyclic or linear form and have a wide

Carbon and nitrogen metabolism are intricately linked in all organisms and are tightly regulated to maintain growth, homeostasis, and other cellular activities. In plants and algae, photosynthesis provides both carbon skeletons and the reductant needed for assimilation of inorganic NO3− by nitrate