Catabolite repression is exerted through a second messenger called cyclic AMP (cAMP) and the positive regulator protein called the catabolite repressor protein (CRP), a dimer.

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#Unit 6. System Physiology – Plant

phot1 is the primary phototropic receptor mediates phototropism in response to low and high fluence rates of blue light. 

phot2 mediates phototropism in response to high light intensities

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#Id: 9858

#Unit 6. System Physiology – Plant

Phototropin receptors are associated with the plasma membrane, where they function as light-activated serine/threonine kinases.

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#Unit 6. System Physiology – Plant

Phototropin contains two light-sensing LIGHT-OXYGEN-VOLTAGE (LOV) domains, LOV1 and LOV2, each binding a chromophore flavin mononucleotide (FMN).

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#Id: 9860

#Unit 6. System Physiology – Plant

In the dark, the maximum absorption of the FMN chromophore is around 450 nm. 

Blue light induces the formation of a covalent bond between FMN and a cysteine residue, shifting the absorption maximum to 390 nm via a LOV660 intermediate form. The reaction is reversible in darkness.

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#Unit 6. System Physiology – Plant

LOV2 domain is essential for blue light–induced kinase activation and autophosphorylation of the phototropin photoreceptor.

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#Id: 9862

#Unit 6. System Physiology – Plant