biology

UVR8

UVR8 is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand UVR8 rather than just read about it. In short: UV-B resistance 8 (UVR8) also known as ultraviolet-B receptor UVR8 is an UV-B – sensing protein found in plants and possibly other sources. It is responsible for sensing ultraviolet light in the range 280-315 nm and initiating the plant stress response.

Key takeaways

UVR8 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect UVR8 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of UVR8 from memory before moving on to harder problems.

Reference excerpt

UV-B resistance 8 (UVR8) also known as ultraviolet-B receptor UVR8 is an UV-B – sensing protein found in plants and possibly other sources. It is responsible for sensing ultraviolet light in the range 280-315 nm and initiating the plant stress response. It is most sensitive at 285nm, near the lower limit of UVB. UVR8 was first identified as a crucial mediator of a plant's response to UV-B in Arabidopsis thaliana containing a mutation in this protein. This plant was found to have a hypersensitivity to UV-B which damages DNA. UVR8 is thought to be a unique photoreceptor as it doesn't contain a prosthetic chromophore but its light-sensing ability is intrinsic to the molecule. Tryptophan (Trp) residue 285 has been suggested to act the UV-B sensor, while other Trp residues have been also seen to be involved (Trp233 > Trp337 > Trp94) although in-vivo data suggests that Trp285 and Trp233 are most important.

Evolution Although the complete genome sequence is only available from a limited number of angiosperms, bioinformatic analysis suggests that there are a large number of UVR8 orthologs. Both number and position of key residues seem to be well conserved among angiosperms but also other plant species (e.g., Chlamydomonas reinhardtii and Volvox carteri). The latter implies that UVR8 potentially appeared before the evolutionary split in vascular land plants which would be rational considering that at that time the amount of UV-B radiation that penetrated the earth surface was higher as the ozone layer was not fully developed, hence UV protection and acclimation would be of crucial importance.

Structure UVR8 is a β-propeller protein with 7 blade-shaped β-sheets. It shares sequence homology with mammalian proteins involved in regulating chromatin condensation, for example the human RCC1 gene product. In the dark state, UVR8 forms a homodimer that is localized in the cytosol, but UV-B illumination induces the dissociation of UVR8 dimer to its respective monomers and translocation to the nucleus occurs. The dimer is held together via a complex salt bridge network.

Mechanism Upon UV-B irradiation, light is absorbed by one or more Trp residues which are situated adjacent to Arg residues which form salt bridges across the dimer interface. It is thought that this light absorption induces the disruption of the salt-bridges and thus leads to the molecule's monomerization. Following monomerization, UVR8 accumulates in the nucleus where it interacts with a protein called constitutively photomorphogenic 1 (COP1). COP1 is known to act as an E3 Ubiquitin ligase that targets key transcription factors for ubiquitination and proteasome-mediated degradation. However, in the case of UVR8, it has been shown to act as a positive regulator of UVR8-mediated UV-B signalling. Upon UV-B illumination, UVR8 interacts via a C-terminal 27 amino acid region with the WD40 domain of COP1 in the nucleus, which triggers the induction of ELONGATED HYPOCOTYL 5 (HY5) — a key transcription factor for several UV-B responsive genes, and overall results in UV-B acclimation.

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with UVR8

Start with the simplest possible case. Write down what UVR8 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to UVR8 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about UVR8 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of UVR8

In research: UVR8 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses UVR8 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: UVR8 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Plant proteins, so understanding it makes those chapters shorter.
In everyday life: Look for UVR8 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study UVR8 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what UVR8 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain UVR8 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is UVR8 in simple terms?

Why does UVR8 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study UVR8?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on UVR8.