The Next Frontier: Proteome Dynamics and Fungal Pathogenicity.

Magnaporthe oryzae, the causative agent of rice blast disease, infects plant leaves via formation of an appressorium which facilitates penetration of the leaf surface.  In an effort to better understand the physiological changes accompanying the earliest stages of infection-related development, a nano-LC MS/MS-based global proteomics examination of conidial germination and cAMP-induced appressoria formation resulted in the identification of over 5000 proteins. In developing appressoria, changes in cell wall modifiying, transport, extracellular and plasma membrane localized proteins were observed. A comparison of proteome and transcriptome data revealed little correlation between protein and transcript regulation.  To better define the role of protein phosphorylation, study of the phosphoproteome was undertaken.  A total of 2924 class I phosphosites were identified from 1514 phosphoproteins. Network analysis incorporating regulation from transcriptomic, proteomic and phosphoproteomic data revealed new insights into the regulation of the metabolism of conidial storage reserves and phospholipids, autophagy, actin dynamics and cell wall metabolism during appressorium formation. In particular, protein phosphorylation appears to play a central role in the regulation of autophagic recycling and actin dynamics during appressorium formation.  Changes in phosphorylation were observed in multiple components of the cell wall integrity pathway as well as several transcription factors.  Functional analysis of MGG_05709 provided further evidence for the role of protein phosphorylation in regulation of glycerol metabolism and the metabolic reprogramming characteristic of appressorium formation. Ubiquitination, plays a key role in the infection process.   Current work is focused on examining global changes in phosphorylation-dependent ubiquitionation.