Mutations causing constitutive invertase synthesis in yeast: genetic interactions with snf mutations

Area of Science:

• Molecular Biology
• Yeast Genetics
• Gene Regulation

Background:

• Secreted invertase synthesis in yeast is typically repressed by glucose.
• Understanding the genetic control of this glucose repression is crucial for metabolic studies.

Purpose of the Study:

• To identify and characterize novel genes involved in constitutive (glucose-insensitive) secreted invertase synthesis.
• To elucidate the genetic interactions and functional relationships of these genes with known regulatory elements.

Main Methods:

• Selection of yeast mutants exhibiting growth on sucrose in the presence of 2-deoxyglucose.
• Complementation analysis to identify distinct genetic groups.
• Construction and analysis of reporter gene fusions (SUC2-LEU2-lacZ) to assess gene expression.
• Epistasis analysis to determine the order of gene function in regulatory pathways.

Main Results:

• Identified three complementation groups of recessive mutations: HXK2, REG1, and a novel gene, cid1.
• Demonstrated that cid1 mutations mediate glucose-insensitive expression via the SUC2 upstream regulatory region and affect maltase expression.
• Established that ssn6 and SNF gene mutations are epistatic to cid1, reg1, and hxk2, indicating distinct roles from SSN6 and TUP1.

Conclusions:

• CID1, REG1, and HXK2 represent distinct genetic components regulating invertase synthesis.
• These genes are functionally separate from the SSN6 and TUP1 regulatory factors.
• The findings provide a deeper understanding of the complex genetic network controlling glucose repression in yeast.