Abstract:
This project was aimed to study the phosphorylation or dephosphorylation of the proteins involved in glucose sensing, signal transduction and glucose repression pathways by transcription of genes encoding these proteins. S. cerevisiae BY4743 strains (ho /ho , hap4 /hap4 , rip1 /rip1 and RIP1/rip1 ) were cultivated under carbon limited condition in order to identify the variations in the expression levels of genes involved in glucose sensing, signal transduction and glucose repression pathways as a response to system level perturbations. Metabolite profiles for glucose, ethanol, ammonia and glycerol were obtained. Expression profiles to be investigated were of CYC8, GRR1, MTH1, RGT1, RGT2, SKP1, SNF3, STD1,TUP1, YCK1, YCK2, ELM1, GLC7,HXK2, MIG1, PAK1, REG1, SNF1, SNF4, TOS3, HAP4, MBA1 genes. The highest cell density in steady state was seen in rip1 /rip1 strain. The respiratory deficient strains hap4 /hap4 and rip1 /rip1 produced maximum ethanol. The expression of HAP4 downregulated in ho / ho strain, and was upregulated in both deletion mutants of RIP1 of S. cerevisiae showing the lack of the response of HAP4 to glucose pulse caused by respiratory deficiency. MTH1, STD1, YCK1 and YCK2 genes were downregulated in the strains ho /ho , hap4 /hap4 and RIP1/rip1 , and upregulated in the homozygous deletion mutant of RIP1. REG1, GLC7, MIG1, SNF1 and SNF4 genes are upregulated with carbon pulse suggesting their involvement in the glucose repression pathway. MBA1 gene expression upregulated after carbon pulse in ho /ho , rip1 /rip1 and RIP1/rip1 strains, however for the HAP4 deletion mutant, the response to pulse injection wasn’t immediate.
