biology

Late Elongated Hypocotyl

Late Elongated Hypocotyl 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 Late Elongated Hypocotyl rather than just read about it. In short: The Late Elongated Hypocotyl gene (LHY), is an oscillating gene found in plants that functions as part of their circadian clock. LHY encodes components of mutually regulatory negative feedback loops with Circadian Clock Associated 1 (CCA1) in which overexpression of either results in dampening of both of their expression.

Key takeaways

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

Reference excerpt

The Late Elongated Hypocotyl gene (LHY), is an oscillating gene found in plants that functions as part of their circadian clock. LHY encodes components of mutually regulatory negative feedback loops with Circadian Clock Associated 1 (CCA1) in which overexpression of either results in dampening of both of their expression. This negative feedback loop affects the rhythmicity of multiple outputs creating a daytime protein complex. LHY was one of the first genes identified in the plant clock, along with TOC1 and CCA1. LHY and CCA1 have similar patterns of expression, which is capable of being induced by light. Single loss-of-function mutants in both genes result in seemingly identical phenotypes, but LHY cannot fully rescue the rhythm when CCA1 is absent, indicating that they may only be partially functionally redundant. Under constant light conditions, CCA1 and LHY double loss-of-function mutants fail to maintain rhythms in clock-controlled RNAs. The circadian clock in plants has completely different components to those in the animal, fungus or bacterial clocks. The plant clock does have a conceptual similarity to the animal clock in that it consists of a series of interlocking transcriptional feedback loops. The genes involved in the clock show their peak expression at a fixed time of day. The peak expression of the CCA1 and LHY genes occurs at dawn, and the peak expression of the TOC1 gene occurs roughly at dusk. CCA1/LHY and TOC1 proteins repress the expression of each other's genes. The result is that as CCA1/LHY protein levels start to reduce after dawn, it releases the repression on the TOC1 gene, allowing TOC1 expression and TOC1 protein levels to increase. As TOC1 protein levels increase, it further suppresses the expression of the CCA1 and LHY genes. The opposite of this sequence occurs overnight to re-establish the peak expression of CCA1 and LHY genes at dawn. CCA1 is generally a more significant component of this oscillator. Light induces its transcription, and mRNA levels peak at dawn along with LHY. CCA1 and LHY associate to inhibit transcription of the Evening Complex (EC) proteins: ELF4, ELF3 and LUX, which suppresses their accumulation until dusk when LHY and CCA1 protein levels are at their lowest. Four primary pseudo-response regulator proteins (PRR9, PRR7, PRR5 and TOC1/PRR1) perform the majority of interactions with other proteins within the circadian oscillator, and another (PRR3) that has limited function. These genes are all paralogs of each other, and all repress the transcription of CCA1 and LHY at various times throughout the day. Plants that have lost function of LHY and CCA1 lose the ability to stably maintain circadian rhythm and other output phenomena. In one study, such plants showed photoperiod- insensitive early flowering under long- day (16 hours of light/ 8 hours of dark) conditions and short day (8 hours of light, 16 hours of dark conditions), and arrhythmicity under constant light conditions. However they retain some circadian function in light/dark cycles, showing that Arabidopsis circadian clock is not completely dependent on CCA1 and LHY activity. Plants with non-functioning LHY and CCA1 show a wavy leaf phenotype in constant light conditions. Mutants also have increased vascular pattern complexity in their leaves, with more areoles, branch points and free ends than wild-type Arabidopsis. The function of LHY was initially identified as a dominant late flowering transposon-tagged mutant in the Coupland lab of the John Innes center (UK) [1]

References

Attribution: This article contains material originally copied from Circadian clock, Circadian Clock Associated 1, Oscillating gene, and Pseudo-response regulator.

Worked examples

Example 1 — a first encounter with Late Elongated Hypocotyl

Start with the simplest possible case. Write down what Late Elongated Hypocotyl 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 Late Elongated Hypocotyl 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 Late Elongated Hypocotyl 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 Late Elongated Hypocotyl

In research: Late Elongated Hypocotyl 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 Late Elongated Hypocotyl 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: Late Elongated Hypocotyl is common in secondary-school and first-year university syllabi. It links to neighbouring topics Circadian rhythm, Plant genes, so understanding it makes those chapters shorter.
In everyday life: Look for Late Elongated Hypocotyl 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 Late Elongated Hypocotyl in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Late Elongated Hypocotyl 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 Late Elongated Hypocotyl out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Late Elongated Hypocotyl in simple terms?

Why does Late Elongated Hypocotyl 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 Late Elongated Hypocotyl?

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 Late Elongated Hypocotyl.