Phytochrome Stability in Vitro: II. A Low Molecular Weight Protective Factor

Area of Science:

• Plant Physiology
• Biochemistry

Background:

• Phytochrome is a plant photoreceptor crucial for light-mediated development.
• Phytochrome preparations can degrade in vitro, affecting experimental reliability.

Purpose of the Study:

• To identify and characterize a factor that protects phytochrome from degradation in vitro.
• To investigate the properties and potential mechanism of this protective factor.

Main Methods:

• Spectrophotometric measurement of phytochrome photoreversibility decline.
• Assessing the effect of a pea-derived factor on phytochrome stability.
• Determining the factor's molecular weight, stability (temperature, oxygen, light), optimal pH, and enzyme resistance.
• Evaluating the factor's protection against Cu(2+)-induced phytochrome decay.

Main Results:

• A protective factor from green pea tissue was identified.
• The factor has an apparent molecular weight of 465 and is stable to heat, oxygen, and high light.
• Optimal protection occurred at pH ~7.8 and was largely unaffected by hydrolytic enzymes.
• The factor protected phytochrome from Cu(2+)-accelerated decay, suggesting metal chelation.

Conclusions:

• An endogenous factor in peas significantly retards in vitro phytochrome decay.
• This protective factor exhibits robust stability and optimal activity at neutral to alkaline pH.
• The factor's ability to counteract copper-induced degradation implies a role as a metal chelator, potentially preserving phytochrome integrity.