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PhyB - Functions, Effects And Importance For Plant Growth

In a temperature-dependent way, phyB connects with the promoters of important target genes.

Suleman Shah
Jul 28, 202342377 Shares596856 Views
PhyBhelps plants respond to many environmental challenges by priming them.
Phytochrome (Phy) is a photoreceptor, a pigment used by plants and certain bacteria and fungi to sense light.
Plants use the red (R) and far-red (FR) photoreceptors, phytochrome B (phyB), to detect changes in ambient temperature.
PhyB is a bilin-containing pigment or biliprotein that detects light with the help of a covalently attached phytochromobilin as the chromophore.
It is sensitive to light in the visible spectrum's red and far-red regions.
The responsibilities of phyB as a signaling integrator of numerous surrounding information would help us understand how plants attempt to adapt to co-occurring environmental changes and contribute to the exploration of approaches to building climate-smart crops with greater adaptability to environmental stresses.
The activities of phyB as a signaling integrator of numerous surrounding information will help plants adapt to co-occurring environmental changes and contribute to the exploration of approaches to building climate-smart crops with greater adaptability to environmental stresses.

PhyB Functions

  • Thermotolerance: Temperatures over a physiological range are detrimental to plant growth, development, and survival. To deal with heat stress, plants have developed a variety of thermoadaptive processes. PhyB is essential for the light priming of thermotolerance responses. The photochemical balance between the Pr and Pfr forms is an important signaling component that governs thermotolerance responses. Plants in nature are often subjected to shadows created by neighboring plants. Under those circumstances, phyB would be pushed mostly toward the Pr form, but the temperature would remain high.
  • Cold Tolerance: Cold temperatures hurt plant growth and development, ultimately leading to plant mortality. According to growing research, light responses and cold acclimation share many signaling mediators and regulatory systems. Changing photoperiods have been demonstrated to alter the development of cold tolerance in Arabidopsis.
  • Drought Tolerance: Drought has a negative impact on vegetative growth, metabolism, and reproductive function. Drought stress effects include stomatal closure and a decrease in cell development. Given the simultaneous presence of high temperature, solar irradiance, and dryness, plant response to drought is expected to be connected with light signaling. Light signals mediated by phyB differently affect water preservation in the plant body. PhyB stimulates stomatal opening and development in well-watered conditions.
  • Plant Defense: Two fundamental features of light control of plant defense are shown. Herbivore and pathogen behavioral and physiological characteristics are coordinated with light diel cycles. Another thing to consider is the growth-defense tradeoffs that plants must make. According to recent research, weak signals play a significant role in modifying plant responses. Plants are less sensitive to salicylic acid or jasmonic acid treatments in generating defensive responses under low R/FR conditions. Similarly, salicylic acid sensitivity and systemic acquired resistance are significantly reduced in the phyA-phyB double mutants.
Trees without leaves and grass
Trees without leaves and grass

Is Phytochrome A Hormone?

It is the hormone capable of reversing the effects of other stimulating growth hormones such as gibberellins and cytokinins.
Gibberellins are another crucial plant hormone responsible for seed dormancy, shoot elongation, seed germination, and fruit and flower maturity.

Phytochromes Types

In vivo, phytochromes have two separate yet photoreversible forms: the R light-absorbing form (Pr) and the FR light-absorbing form (Pfr).
The Pr form absorbs the most at 660 nm, whereas the Pfr form absorbs the most at 730 nm.
The Pfr variants of phytochromes are thought to be the most physiologically active.
It should be noted that phytochromes, in addition to their maximum absorptions of R and FR wavelengths, also absorb B light weakly.

Role Of Phytochrome In Flowering

It promotes blooming in short-day plants while suppressing blossoming in long-day plants.
Short-day plants need a longer duration of darkness.
Pfr is transformed into Pr over a lengthy period, which stimulates blooming.
Flowering is hindered when the extended dark phase is disrupted by red light.


The red and far-red light-absorbing phytochrome (phy) photoreceptors, particularly phyB, play an essential role in plant adaptation responses to biotic and abiotic tensions by serving as a critical mediator of information flow.
This allows the phytochrome (phy) photoreceptors to play an essential in plant adaptation.

People Also Ask

What Is A Phyb?

PhyB enhances seed germination by boosting gibberellin production but decreases hypocotyl elongation by lowering gibberellin responsiveness.
PhyB and gibberellins negatively impact blooming later in the plant's lifecycle.
PhyB retards blooming, while gibberellin enhances flowering, especially under noninductive photoperiods.

Where Are Phytochromes Located?

Phytochrome is ordinarily present in the cytoplasm of plant cells.
Still, when it transforms to Pfr, it goes to the nucleus and controls the expression of numerous genes involved in plant developmentand morphology.

How Does Phytochrome B Work?

The primary photoreceptor influencing development in Arabidopsis seedlings exposed to varying shade conditions is phyB.
PhyB, like other phytochrome proteins, is a homodimeric chromoprotein containing a covalently attached phytochromobilin chromophore in each subunit.
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