Phosducin-like protein PoPlp1 impacts cellulase and amylase expression and development in Penicillium oxalicum via the G protein–cAMP signaling pathway

Abstract

In this study, a phosducin-like protein, PoPlp1, was identified and functionally studied in the cellulase-producing strain Penicillium oxalicum 114-2. PoPlp1 was proven to participate in several biological processes, including mycelium development, conidiation, and expression of cellulases and amylases. With deletion of Poplp1, morphology and development varied significantly in ΔPoplp1. Colony growth, glucose utilization, and the hydrolysis capability of starch and cellulose were limited, whereas conidiation was enhanced. Based on detection of the levels of expression of transcription factors involved in asexual development, we conjectured that PoPlp1 is involved in conidiation via the major factor BrlA. We explored the effect of PoPlp1 on cellulase and amylase expression and observed that cellulase and amylase activity and major gene transcription levels were all dramatically reduced in ΔPoplp1. Deletion of PoPlp1 caused a decrease in intracellular cAMP levels, and the cellulase gene expression level of ΔPoplp1 was restored to a certain extent through external addition of cAMP. These findings demonstrate that PoPlp1 may affect cellulase and amylase expression by regulating cAMP concentration. To comprehensively explore the mechanism of PoPlp1 in regulating multiple biological processes, we performed a comparative transcriptomic analysis between strains P. oxalicum 114-2 and ΔPoplp1. The major cellulase and amylase genes were all downregulated, congrent with the results of real-time quantitative polymerase chain reaction analysis. The genes involved in the G protein–cAMP signaling pathway, including several G-protein-coupled receptors, one regulator of G protein signaling, and two cAMP phosphodiesterases, were disrupted by deletion of PoPlp1. These results confirm the positive function of PoPlp1 in the G protein–cAMP signaling pathway. This functional analysis of PoPlp1 will be very beneficial for further study of the regulatory mechanisms of cellulase expression and other biological processes in P. oxalicum 114-2 via the G protein–cAMP signaling pathway.

Functional Study of cAMP-Dependent Protein Kinase A in Penicillium oxalicum

“…The cAMP/PKA signaling pathway plays a crucial role in various cellular processes in eukaryotes, such as carbon and nitrogen metabolism, and reproduction [12,14,23]. In P. oxalicum, the expression of cellulase is closely linked to the cAMP/PKA signaling pathway [3,4]. However, the exact mechanism is not fully understood.…”

“…The regulation of lignocellulase expression in filamentous fungi involves a complex interplay of transcription factors and functional proteins [1,2]. Cell signal transduction pathways are crucial in the induction and control of filamentous fungal enzymes, particularly in environments rich in lignocellulosic substrates [3]. Among these pathways, the protein kinase A (PKA) signal pathway has been identified as a significant component in the regulatory network of cellulase expression in filamentous fungi [4][5][6].…”