Recombinant type A and B phytochromes from potato. Transient absorption spectroscopy

Area of Science:

• Plant molecular biology
• Photochemistry
• Biophysics

Background:

• Phytochromes are plant photoreceptors that regulate growth and development in response to light.
• Understanding the molecular mechanisms of phytochrome signaling is crucial for crop improvement.

Purpose of the Study:

• To express and characterize potato phytochromes (phyA and phyB) in yeast systems.
• To investigate the chromophore incorporation and light-induced signaling kinetics of potato phytochromes.

Main Methods:

• Expression of full-length potato phyA and phyB, and a phyB deletion mutant in Saccharomyces cerevisiae and Pichia pastoris.
• Reconstitution of apoproteins with phytochromobilin (PφB) and phycocyanobilin (PCB) chromophores.
• Spectroscopic analysis (difference absorption) and time-resolved kinetic analysis (nanosecond flash photolysis).

Main Results:

• Potato phyA and phyB reconstituted with PφB showed distinct absorption maxima (Pr and Pfr forms).
• PCB-reconstituted phytochromes exhibited blue-shifted absorption maxima compared to PφB.
• Time-resolved kinetics revealed unique intermediate decay and Pfr formation pathways for phyB, differing from oat phyA.

Conclusions:

• Potato phyA and phyB exhibit distinct spectral and kinetic properties upon chromophore incorporation.
• The light-induced signaling mechanism of potato phyB is unique and differs from other characterized phytochromes.
• This study provides novel insights into the molecular basis of phytochrome function in plants.