Evidence of a New MoYpd1p Phosphotransferase Isoform in the Multistep Phosphorelay System of Magnaporthe oryzae

Abstract

Different external stimuli are perceived by multiple sensor histidine kinases and transmitted by phosphorylation via the phosphotransfer protein Ypd1p in the multistep phosphorelay system of the high osmolarity glycerol signaling pathway of filamentous fungi. How the signal propagation takes place is still not known in detail since multiple sensor histidine kinase genes in most filamentous fungi are coded in the genome, whereas only one gene for Ypd1p exists. That raises the hypothesis that various Ypd1p isoforms are produced from a single gene sequence, perhaps by alternative splicing, facilitating a higher variability in signal transduction. We found that the mRNA of MoYPD1 in the rice blast fungus Magnaporthe oryzae is subjected to an increased structural variation and amplified putative isoforms on a cDNA level. We then generated mutant strains overexpressing these isoforms, purified the products, and present here one previously unknown MoYpd1p isoform on a proteome level. Alternative splicing was found to be a valid molecular mechanism to increase the signal diversity in eukaryotic multistep phosphorelay systems.

An array of signal-specific MoYpd1 isoforms determines full virulence in the pathogenic fungusMagnaporthe oryzae

“…Our studies reveal new, previously unknown interactions between MoYpd1p and different HKs that may facilitate and explain the diversity in signal transduction in M. oryzae and explain its virulence. The PPI analyses based on the three-dimensional (3D) structures of the isoforms and the HKs were modulated to gain insight into the physiological functions of MoYpd1p_T0 (MGG_07173T0), MoYpd1p_T1(MGG_07173T1) and MoYpd1p_T2 (Bühring et al 2021). Due to the unpredictable 3D model caused by the size of MoHik6p, it was impossible to calculate its interaction with isoforms.…”

“…Signaling systems, such as phosphorelay systems, generally use proteins containing HPt to transmit signals from sensor HKs to RRs (Alvarez and Georgellis 2022; Jacob et al 2022). Based on RNA-Seq and HPLC-MS/MS analyses, we previously hypothesized that AS may produce several different MoYpd1p isoforms with distinct physiological functions (Bühring et al 2021; Jacob and Thines 2017). Apart from MoSln1p and MoHik1p, MoYpd1p is likely to interact with one or more of the remaining eight HKs (MoHik2p-MoHik9p) identified in M. oryzae (Jacob et al 2014).…”

“…Moreover, a third transcript isoform (MoYPD1_T3) was identified on the cDNA and protein level (Bühring et al 2021). In addition to its key role in the HOG signaling pathway, MoYPD1 appears to positively and negatively influence genes involved in other stress adaptation processes and virulence (Mohanan et al 2022).…”

“…Apart from MoSln1p and MoHik1p, eight further HKs are encoded in the genome of M. oryzae , which may also can perform protein-protein interactions (PPI) with MoYpd1p (Jacob et al 2014). Moreover, a third transcript isoform (MoYPD1_T3) was identified on the cDNA and protein level (Bühring et al 2021). In addition to its key role in the HOG signaling pathway, MoYPD1 appears to positively and negatively influence genes involved in other stress adaptation processes and virulence (Mohanan et al 2022).…”

Special Issue “Signal Transductions in Fungi”

“…In filamentous fungi, the high-osmolarity glycerol (HOG) signaling pathway is present as a multistep phospho-relay system. Bühring et al [ 6 ] investigated the phosphotransferase system in the rice blast fungus Magnaporthe oryzae and addressed the question of how a single gene for a phosphotransfer protein may generate several isoforms to contribute to a multistep phospho-relay system. Their study indicates that alternative splicing is a promising mechanism to generate signal diversity in multistep phospho-relay systems.…”