Statistical analysis of DEGs
RNA transcription data was integrated and intercompared in Figure 2. It is obvious that cellular transcriptional response of yeast cells at P1 was consistent with that at P5 - only 10 DEGs detected, which suggest that yeast cells exhibit similar transcriptional characteristics in the same position of different oscillation periods. This was expected as the end point of one oscillation represents the start point of the following period. It also confirmed the periodic nature of continuous oscillation.
The big DEGs counts between the neighboring points showed the sustained and significant transcriptional changes attributed to the unsteady state of VHG ethanol fermentation. Compared to initial cell status (P1), the curve of total counts of DGEs in P2-5 fitted the biomass curve (π phase). The highest counts of DEGs appeared between P1 and P3 due to the maximum time difference of P3 and P1(or P5 that is equivalent to P1).
The mRNA expression of six selected genes (upregulated during P1-P2-P3 and downregulated during P3-P4-P5) was measured by qRT-PCR. These genes are common differential genes compared by several adjacent points. The trend of gene expression levels in five sampling points of 6 DEGs were consistent with that of RNA-seq, which verified the accuracy of the DEGs from transcriptome analysis (Figure S2).