Transcriptomics-proteomics conjoint analysis of differentially expressed genes/proteins between wild type and ultraviolet radiation-mutated Halomonas campaniensis strains

Abstract:

A mutant strain G₉-72 with a high yield of ectoine was obtained from wild type Halomonas campaniensis after nine rounds of ultraviolet mutagenesis. The differentially expressed genes/proteins (DEGs/DEPs) and the molecular mechanism underlying the excessive increase in the ectoine yield remain to be explored for the mutant strain.Objective To explore the DEGs/DEPs between the wild type strain XH26 and G₉-72 and decipher the molecular mechanism of efficient ectoine production by conjoint analysis.Methods A non-salt (NS, 0 mol/L NaCl) group and a high-salt (HS, 1.5 mol/L NaCl) group were designed for the culture of XH26 and G₉-72. Illumina HiSeq and quantitative mass spectrometry were employed to identify the DEGs/DEPs between the two strains by transcriptomics-proteomics conjoint analysis. Furthermore, RT-qPCR was carried out to verify the expression of significant DEGs.Results The transcriptomics analysis revealed 11 amino acid metabolic pathways (44 DEGs) associated with ectoine anabolism, and the proteomics analysis revealed ten amino acid metabolic pathways (50 DEPs) associated with ectoine anabolism. The transcriptomics-proteomics conjoint analysis identified 15 significant DEGs, including seven genes (ectB, betB, betA, asd, doeD, doeC, and gabD) with up-regulated mRNA and protein level, four genes (ItaE, gdhA, gabT, and acnB) with down-regulated mRNA and protein levels, three genes (gltD, atoB, and narG) with down-regulated mRNA levels and up-regulated protein levels, and one gene narK with up-regulated mRNA level and no protein level. Additionally, the RT-qPCR results were consistent with the transcriptomics analysis.Conclusion The excessive increase in the ectoine yield of the mutant strain was associated with key genes in the ectoine metabolic pathway (including the synthesis genes asd and ectB and the catabolism genes doeD and doeC) and indirectly associated with several genes (betB, betA, ItaE, gltD, gadA, and acnB) in the upstream metabolic pathway. Notably, ectoine biosynthesis was highly associated with the Ala/Asp/Glu/His metabolic pathway (gabD, gdhA, gabT, and atoB) and nitrogen source metabolism (narK and narG).