An unstable nuclear gene in phycomyces.

Area of Science:

• * Genetics
• * Molecular Biology
• * Mycology

Background:

• * Phycomyces exhibits genetic instability linked to a specific nuclear gene, designated dar.
• * Wild-type strains efficiently uptake riboflavin and its toxic analog, deaza-riboflavin, even at low concentrations.
• * Mutants display impaired riboflavin uptake and resistance to deaza-riboflavin, suggesting a role in transport mechanisms.

Purpose of the Study:

• * To characterize the genetic instability associated with the dar gene in Phycomyces.
• * To investigate the role of the dar gene in riboflavin and deaza-riboflavin transport.
• * To determine the mutation rates and allelic interactions of dar mutants.

Main Methods:

• * Genetic analysis of Phycomyces strains.
• * Heterokaryon complementation tests.
• * Measurement of riboflavin and deaza-riboflavin uptake.
• * Estimation of forward and reverse mutation rates.

Main Results:

• * A single nuclear gene, dar, is identified as responsible for the observed genetic instability.
• * dar mutants are unable to uptake riboflavin and exhibit resistance to deaza-riboflavin.
• * Forward and reverse mutation rates were estimated at 4 x 10(-5) and 2 x 10(-3) per nuclear division, respectively.
• * Mutants showed no complementation in heterokaryons and were largely recessive.
• * Spore phenotype was influenced by the allele ratio within the sporangium.

Conclusions:

• * The dar gene plays a critical role in riboflavin uptake and deaza-riboflavin resistance in Phycomyces.
• * The dar gene is essential for maintaining genetic stability.
• * The recessive nature and non-autonomous phenotype suggest complex genetic interactions and regulation.