Decreased expression of LRA4, a key gene involved in rhamnose metabolism, caused up-regulated expression of the genes in this pathway and autophagy in Pichia pastoris

Abstract

In a previous study, we developed Pichia pastoris GS115m, an engineered strain with decreased expression of one key gene, LRA4, in rhamnose metabolism. P. pastoris GS115m/LacB was subsequently constructed via introducing a β-galactosidase gene, LacB, under the control of rhamnose-inducible P LRA3 into P. pastoris GS115m. P. pastoris GS115m/LacB greatly improved recombinant protein production relative to the parental strain (P. pastoris GS115/LacB). In the present study, transcriptomes of P. pastoris GS115m/LacB and P. pastoris GS115/LacB grown in YPR medium were analyzed. P. pastoris GS115m/LacB was found to suffer from the mild carbon source starvation. To attenuate the starvation stress, P. pastoris GS115m/LacB attempted to enhance rhamnose metabolism by elevating the transcription levels of rhamnose-utilization genes LRA1-3 and RhaR. The transcription level of LacB under the control of P LRA3 thereby increased, resulting in the improved production of recombinant protein in P. pastoris GS115m/LacB. It was also revealed that P. pastoris GS115m/LacB cells coped with carbon starvation mostly via autophagy.

Identification of the genes encoding the catalytic steps corresponding to LRA4 (l‐2‐keto‐3‐deoxyrhamnonate aldolase) and l‐lactaldehyde dehydrogenase in Aspergillus nidulans: evidence for involvement of the loci AN9425/lraD and AN0544/aldA in the l‐rhamnose catabolic pathway

“…α‐ l ‐Rhamnosidase activities release l ‐rhamnose and are of considerable interest for their biotechnological applications in the pharmaceutical, food, agro‐alimentary and chemical industries (reviewed in Manzanares et al ., 2007; Yadav et al ., 2010), and a number of studies on the regulation of their production have been undertaken in Aspergillus nidulans (Orejas et al ., 1999; Manzanares et al ., 2000; Bauer et al ., 2006; Tamayo‐Ramos et al ., 2012; MacCabe et al ., 2020). The microbial pathways by which l ‐rhamnose is catabolized have been studied since the 1950s for their scientific and practical interest (Wilson and Ajl, 1955; Kuivanen and Richard, 2016; Yan et al ., 2018; Diallo et al ., 2019; Jiao et al ., 2020). As shown in Fig.…”