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The plant cell wall structure can be altered by pathogen-secreted polygalacturonases (PGs) that cleave the α-(1→4) linkages occurring between D-galacturonic acid residues in homogalacturonan. The activity of the PGs leads to cell wall maceration, facilitating infection. Plant PG inhibiting proteins (PGIPs) impede pathogen PGs, impairing infection and leading to the ability of the plant to resist infection. Analyses show the Glycine max PGIP11 (GmPGIP11) is expressed within a root cell that is parasitized by the pathogenic nematode Heterodera glycines, the soybean cyst nematode (SCN), but while undergoing a defence response that leads to its demise. Transgenic experiments show GmPGIP11 overexpression leads to a successful defence response, while the overexpression of a related G. max PGIP, GmPGIP1 does not, indicating a level of specificity. The analyses presented here have identified PGIPs from 51 additional studied proteomes, many of agricultural importance. The analyses include the computational identification of signal peptides and their cleavage sites, O-, and N-glycosylation. Artificial intelligence analyses determine the location where the processed protein localize. The identified PGIPs are presented as a tool base from which functional transgenics can be performed to determine whether they may have a role in plant-pathogen interactions.

The endomembrane system, functioning in secretion, performs many roles relating to eukaryotic cell physiological processes and the Golgi apparatus is the central organelle in this system. An essential associated Golgi component is the conserved oligomeric Golgi (COG) complex, maintaining correct Golgi structure and function during retrograde trafficking. In animals, naturally occurring cog mutants provide a window into understanding it’s function(s). Eliminating even one COG component impairs its function. In animals, COG mutations lead to severe cell biological and developmental defects and death while far less is understood in plants which is changing. The plant genetic model Arabidopsis thaliana COG complex functions in growth, cell expansion and other processes, involving direct interactions with other secretion system components including the exocyst, soluble N-Ethylmaleimide-Sensitive Factor Attachment Protein Receptor (SNARE), and the microtubule cytoskeleton. Recent experiments have identified a defense role for the COG complex in plants, the focus of this review.

Glycine max has 32 mitogen activated protein kinases (MAPKs), nine of them exhibiting defense functions (defense MAPKs) to the plant parasitic nematode Heterodera glycines. RNA seq analyses of transgenic G. max lines overexpressing (OE) each defense MAPK has led to the identification of 309 genes that are increased in their relative transcript abundance by all 9 defense MAPKs. Here, 71 of those genes are shown to also have measurable amounts of transcript in H. glycines-induced nurse cells (syncytia) produced in the root that are undergoing a defense response. The 71 genes have been grouped into 7 types, based on their expression profile. Among the 71 genes are 8 putatively-secreted proteins that include a galactose mutarotase-like protein, pollen Ole e 1 allergen and extensin protein, endomembrane protein 70 protein, O-glycosyl hydrolase 17 protein, glycosyl hydrolase 32 protein, FASCICLIN-like arabinogalactan protein 17 precursor, secreted peroxidase and a pathogenesis-related thaumatin protein. Functional transgenic analyses of all 8 of these candidate defense genes that employ their overexpression and RNA interference (RNAi) demonstrate they have a role in defense. Overexpression experiments that increase the relative transcript abundance of the candidate defense gene reduces the ability that the plant parasitic nematode Heterodera glycines has in completing its life cycle while, in contrast, RNAi of these genes leads to an increase in parasitism. The results provide a genomic analysis of the importance of MAPK signaling in relation to the secretion apparatus during the defense process defense in the G. max-H. glycines pathosystem and identify additional targets for future studies.