'Protective cloak' prevents plants from self-harming in very bright conditions
Integration of environmental signals on the expression of the photoprotection-related genes. (A) Schematic summary of changing light quality and quantity throughout the day. Blue light reaches deeper levels of the water column, while red light is absorbed near the water surface. In addition, PAR can be strongly reduced by cloud cover, while UV-B radiation might even increase on partly cloudy days. While direct sunlight is shielded/reduced by canopy shading, blue light (and UV light in the case of a plant canopy) reach shaded areas more effectively than other wavelength of PAR through Rayleigh scattering, which increases as the wavelength of light decreases. (B) Signals that regulate energy dissipation in Chlamydomonas. Transcription of LHCSR1, LHCSR3, and PSBS is strongly initiated with exposure to a very low amount of white light (5 μmol of photons m−2 s−1; Fig. 1). This activation is not only strongest for LHCSR3 but also apparent for LHCSR1 and PSBS and is dependent on the Chlamydomonas blue light–dependent photoreceptor PHOT1. All three transcripts are also partially regulated by PET downstream of PSII and the generation of retrograde signals by HL (red). UV-B radiation directly facilitates monomerization of the UVR8 homodimer, which then binds to COP1 and allows the participation of other factors (not included in the figure) in the transcriptional regulation of the photoprotective genes (purple). UV-B exposure may also lead to the generation of RS in the chloroplast that further triggers signaling events (red). In addition, LHCSR3 is strongly controlled by CO2 levels and CIA5, while PSBS may be affected by CO2 to a minor extent (orange). Additional discussion of the role of CO2 in regulating LHCSR3 is presented in Ruiz-Sola et al. (48). The heatmap table summarizes the transcript fold change for each gene in the transition from dark to the indicated conditions. NADP+, nicotinamide adenine dinucleotide phosphate; NADPH, reduced form of NADP+; ADP, adenosine 5′-diphosphate ; ATP, adenosine 5′-triphosphate. Credit: Science Advances (2022). DOI: 10.1126/sciadv.abn1832

New work led by Carnegie's Petra Redekop, Emanuel Sanz-Luque, and Arthur Grossman explores how plants protect themselves from self- harm. Our understanding of one of the most important biochemical processes on Earth has been improved by their findings.

The sun's energy can be converted into chemical energy by plants, algae, and certainbacteria. It is responsible for the oxygen-rich nature of our atmosphere.

Life as we know it couldn't exist without photosynthesis.

The process is done in two phases. In the first, light is absorbed and used to synthesise energy molecule with water and oxygen as a result. The second stage uses carbon dioxide from the air to make sugar.

Plants are exposed to the sun for photosynthesis. Access to sunlight can be affected by a number of factors, including weather, clouds, and canopy cover.

How do plants deal with variability?

"It's necessary for plants and algae to be able to harvest sufficient light when they're in the shade and to diminish the amount of absorbed energy when light conditions are intense, such as at high noon," said Redekop.

Plants and algae can be damaged by highly reactive oxygen molecule if they aren't taken care of. Plants and algae have evolved ways to quickly quench the excess light energy before it can cause harm.

Redkop, Sanz-Luque, and Grossman, along with colleagues from the University of Grenoble Alpes, characterized the genes that are involved in regulating the expression of the protective proteins in the Chlamydomonas.

The genes are activated by an integrated series of signals with built-in redundancies that help plants and algae to maximize their environmental responses.

A suite of conditions that triggered the genes' activation was revealed by the team's work.

The researchers found that the expression of genes in the dark. This is proof that plants and algae are prepared for the early morning light.

Blue light increases from dawn to midday and decreases from noon to sunset, which causes the activation of the genes. This shows the effectiveness of the system regulating photo protection.

The genes are activated by the presence of UV-B radiation, which is not blocked by cloud cover, allowing algae and plants to track the time of day and prepare for changes in light availability.

The availability of carbon dioxide regulated one of the photo protection genes. Further analysis is required to understand the regulatory network.

This set of regulatory features form a protective cloak that dampens the risk posed by excess light in a rapidly changing environment. Plants and algae have evolved to maintain productivity and minimize harm.

More information: Petra Redekop et al, Transcriptional regulation of photoprotection in dark-to-light transition—More than just a matter of excess light energy, Science Advances (2022). DOI: 10.1126/sciadv.abn1832 Journal information: Science Advances