Plant Pathogenesis-Related Proteins in Defense Mechanisms

The pathogenesis-related (PR) proteins constitute a diverse family of inducible polypeptides that accumulate in plants upon biotic or abiotic stress. Classified into at least seventeen classes (PR-1 to PR-17) on the basis of structure and function, these proteins mediate frontline defence through direct antimicrobial activity, hydrolytic enzyme functions, modulation of cell death pathways and the generation of defence signalling molecules. The PR-1 family, characterised by the conserved CAP (cysteine-rich secretory, antigen 5, pathogenesis-related 1) domain, releases a C-terminal CAPE peptide that amplifies immune responses, while PR-5 (thaumatin-like) and PR-14 (lipid transfer) proteins stabilise membranes and facilitate pathogen recognition. Enzymatic PRs such as chitinases (PR-3, PR-4, PR-8, PR-11) and β-1,3-glucanases (PR-2) degrade pathogen cell walls, and ribonucleases contribute to RNA degradation in infected tissues. Beyond intrinsic antimicrobial properties, PR proteins form multi-component complexes and interact with host and pathogen factors, underpinning their global significance in crop protection and sustainable agriculture.

Research from Nature Portfolio

Recent studies have revealed how filamentous pathogens exploit PR-1-like proteins to undermine plant immunity. Research on the fungal pathogen Ustilago maydis showed that its PR-1-like effector protein possesses dual domains that sense host phenolic compounds and trigger hyphal differentiation, thereby promoting colonisation. The pathogen co-opts host cathepsin B-like proteases to cleave the conserved CNYD motif, liberating a CAPE-like peptide that suppresses salicylic acid-mediated defences. Strikingly, this cleavage specificity spares the plant’s own PR-1 proteins, illustrating a refined virulence strategy that directly subverts the CAPE-mediated immune amplification cascade.

Plant Pathogenesis-Related Proteins in Defense Mechanisms publication trend

The graph below shows the total number of articles in plant pathogenesis-related proteins in defense mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Pathogenesis-related (PR) proteins: Inducible plant proteins that accumulate in response to stress and mediate defence through antimicrobial or enzymatic activity.

CAP domain: Conserved cysteine-rich domain in PR-1 proteins that binds lipids and gives rise to defence-amplifying CAPE peptides.

CAPE peptide: C-terminal peptide released from PR-1 proteins that functions as a signalling molecule to enhance immune responses.

Ubiquitin-proteasome system (UPS): Cellular machinery that tags proteins with ubiquitin for degradation, regulating protein abundance and defence signalling.

Chitinase: Enzyme (PR-3/4/8/11) that hydrolyses chitin in fungal cell walls, contributing to antifungal defence.

β-1,3-glucanase: Enzyme (PR-2) that degrades β-1,3-glucans in pathogen cell walls, facilitating pathogen clearance.

References

1. Ustilago maydis PR-1-like protein has evolved two distinct domains for dual virulence activities. Nature Communications (2023).
2. NbMLP43 Ubiquitination and Proteasomal Degradation via the Light Responsive Factor NbBBX24 to Promote Viral Infection. Cells (2023).
3. The function of plant PR1 and other members of the CAP protein superfamily in plant–pathogen interactions. Molecular Plant Pathology (2023).
4. Pathogenesis-Related Proteins (PRs) with Enzyme Activity Activating Plant Defense Responses. Plants (2023).