Transcriptome comparison of Rhizopus chinensis mycelia with different morphology in submerged fermentation for lipase production

Abstract:

[Background] Filamentous fungi are important production strains in fermentation industry, and their morphology is related with the production of target products. Rhizopus chinensis CCTCC M201021 is an important filamentous fungus isolated from Daqu for Chinese liquor, produces some important industrial enzymes, such as lipases. [Objective] Rhizopus chinensis CCTCC M201021 can form two typical mycelia morphology, the aggregated and dispersed, in submerged culture with different fermentation performance. The objective of this work was to study the intrinsic difference associated with different mycelia morphology based on transcriptome profiles of R. chinensis. [Methods] Based on high throughput RNA sequencing, gene transcriptions of high expression and significantly differential expression from R. chinensis mycelia with different morphology were compared. [Results] RNA sequencing released the significant difference in the transcriptomes of mycelia with different morphology. In the 20 genes featuring the highest RPKM values in the transcriptome of the aggregated or dispersed mycelia, most genes with the highest RPKM value were ribosomal proteins genes in the aggregated mycelia. Chitinase genes and signal transduction genes were found in the dispersed R. chinensis in addition to some ribosomal proteins genes. Analysis of 20 most up-regulated genes in the transcriptome of the aggregated or dispersed mycelia indicated that differential genes associated with cellular process and signaling were up-regulated in dispersed mycelia, besides significantly differential genes related to metabolism. The value of RPKM suggested that most of unique transcribed genes in both mycelia were transcribed at a low level, whereas those in the aggregated mycelia were more various and with higher value of RPKM than the dispersed one. Moreover, the higher lipase activity of aggregated R. chinensis agreed with the higher transcription level in the cells. [Conclusion] Our findings indicate intrinsic mechanisms of mycelia morphology differentiation and their influence on metabolism.