The N‐terminal region of the Neurospora NDR kinase COT1 regulates morphology via its interactions with MOB2A/B

Abstract

Summary Nuclear Dbf2p-related (NDR) protein kinases are important for cell differentiation and polar morphogenesis in various organisms, yet some of their functions are still elusive. Dysfunction of the Neurospora crassa NDR kinase COT1 leads to cessation of tip extension and hyperbranching. NDR kinases require the physical interaction between the kinase’s N-terminal region (NTR) and the MPS1-binding (MOB) proteins for their activity and functions. To study the interactions between COT1 and MOB2 proteins, we mutated several conserved residues and a novel phosphorylation site within the COT1 NTR. The phenotypes of these mutants suggest that the NTR is required for COT1 functions in regulating hyphal elongation and branching, asexual conidiation and germination. Interestingly, while both MOB2A and MOB2B promote proper hyphal growth, they have distinct COT1-dependent roles in regulation of macroconidiation. Immunoprecipitation experiments indicate physical association of COT1 with both MOB2A and MOB2B, simultaneously. Furthermore, the binding of the two MOB2 proteins to COT1 is mediated by different residues at the COT1 NTR, suggesting a hetero-trimer is formed. Thus, although MOB2A/B may have some overlapping functions in regulating hyphal tip extension, their function is not redundant and they are both required for proper fungal development.

Functions of the nicotinamide adenine dinucleotide phosphate oxidase family in Ganoderma lucidum: an essential role in ganoderic acid biosynthesis regulation, hyphal branching, fruiting body development, and oxidative‐stress resistance

“…Images were recorded and processed using the NIS‐Elements F package (a software developed by Nikon Corporation, Japan). Hyphal branching was quantified as described by Carmit Ziv et al ., ().…”

Functional analysis of the role of glutathione peroxidase (GPx) in the ROS signaling pathway, hyphal branching and the regulation of ganoderic acid biosynthesis in Ganoderma lucidum

“…The images were recorded and processed using the NIS-Elements F package (Nikon Corporation, Japan). Hyphal branching was quantified according to Ziv et al (2013).…”

Altering Neurospora crassa MOB2A exposes its functions in development and affects its interaction with the NDR kinase COT1

“…Based on their phenotype as well as their physical interactions with COT1, it has been suggested that MOB2A and MOB2B may have many overlapping functions (Maerz et al ., ). Nonetheless, we have previously established the fact that there are differences in the strength of the physical interactions between COT1 and the two MOB proteins and that MOB2B, but not MOB2A, is involved in negative control of asexual conidial production via the COT1 pathway (Maerz et al ., ; Ziv et al ., ). Thus, while overlapping functions exist, under certain conditions, the two proteins lack compensatory capabilities.…”

“…The N. crassa COT1 protein and its homologues in other fungi have been shown to regulate hyphal elongation and branching (Yarden et al ., ; Buhr et al ., ; Dürrenberger and Kronstad, ; Mcnemar and Fonzi, ; Scheffer et al ., ; Johns et al ., ; Ziv et al ., ; Kodama et al ., ). While evidence for the role of phosphorylation concerning the function of COT1 and other NDR kinases has accumulated (Millward et al ., ; Mah et al ., ; Emoto et al ., ; Hou et al ., ; Stegert et al ., ; Ziv et al ., ), no evidence for potential phosphorylative regulation of MOB proteins in N. crassa has been provided to date. Nonetheless, phosphorylative regulation of MOB proteins in other systems has accumulated.…”

“…Additionally, COT1 (NCU07296.7) kinase activity was shown to be reduced in both Δmob‐2a and Δmob‐2b mutants and almost abolished in the Δmob‐2a ; Δmob‐2b double mutant. Both MOB2A and MOB2B have been shown to physically interact with the N‐terminal region of COT1 (Maerz et al ., ; Ziv et al ., ). Based on their phenotype as well as their physical interactions with COT1, it has been suggested that MOB2A and MOB2B may have many overlapping functions (Maerz et al ., ).…”