Germin-Like Proteins and Plant Defense Mechanisms

Germin-like proteins (GLPs) constitute a ubiquitous multigene family in higher plants, characterised by conserved cupin domains and a range of enzymatic activities that underpin basal and induced defence responses. Originally identified as markers of germination, GLPs have been shown to possess oxalate oxidase and superoxide dismutase activities that generate hydrogen peroxide, a central reactive oxygen species (ROS) signal in plant immunity. Their roles extend from cell wall reinforcement via lignification and callose deposition to modulation of phytohormone-mediated pathways, notably jasmonic acid and salicylic acid circuits. Gene duplication and cluster organisation have driven expansion of GLP repertoires in cereals, legumes and horticultural species, enabling both quantitative and broad-spectrum resistance to fungal and bacterial pathogens. Spatial–temporal regulation of GLP expression underpins responses to abiotic stresses such as drought or high temperature, as well as to pathogen-associated molecular patterns (PAMPs). Advances in transgenic and gene-silencing approaches have highlighted the potential for harnessing GLPs in crop improvement, while genome-wide surveys across diverse taxa continue to reveal novel family members and regulatory networks. Together, these discoveries underscore the global significance of GLPs as versatile mediators of plant defence and developmental processes.

Research from Nature Portfolio

Molecular analysis in cotton has demonstrated that a specific GLP (GhGLP2) functions as a positive regulator of resistance to Verticillium dahliae and Fusarium oxysporum. Recombinant GhGLP2 exhibited strong superoxide dismutase activity and inhibited fungal spore germination in vitro. Virus-induced gene silencing in Gossypium hirsutum led to enhanced disease susceptibility, reduced callose deposition and increased vascular browning, whereas Arabidopsis lines overexpressing GhGLP2 showed elevated cell wall lignification and callose accumulation at infection sites. Enhanced tolerance to oxidative stress was evident under methyl viologen challenge, accompanied by induction of ROS-related and defence-marker genes. These findings confirm GhGLP2 as a key node linking enzymatic ROS production with cell wall fortification and phytohormone-driven defence signalling.

Germin-Like Proteins and Plant Defense Mechanisms publication trend

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

Technical terms

Germin-like protein (GLP): A member of the cupin superfamily in plants, often exhibiting oxalate oxidase or superoxide dismutase activity linked to defence responses.

Superoxide dismutase (SOD): An enzyme that catalyses the dismutation of superoxide radicals into hydrogen peroxide and oxygen, contributing to ROS signalling.

Reactive oxygen species (ROS): Chemically reactive molecules derived from oxygen (e.g. superoxide, hydrogen peroxide) that act as signalling molecules in plant immunity.

Callose deposition: The accumulation of β-1,3-glucan at sites of pathogen attack, forming a barrier to restrict invader spread.

Lignification: The polymerisation of phenolic monomers in the cell wall, reinforcing structural defences against pathogens.

References

1. Germin, a protein marker of early plant development, is an oxalate oxidase. Journal of Biological Chemistry (1993).
2. The Multigene Family Encoding Germin-Like Proteins of Barley. Regulation and Function in Basal Host Resistance. Plant Physiology (2006).
3. A Germin-Like Protein Gene Family Functions as a Complex Quantitative Trait Locus Conferring Broad-Spectrum Disease Resistance in Rice. Plant Physiology (2008).
4. Promoters of the Barley Germin-Like GER4 Gene Cluster Enable Strong Transgene Expression in Response to Pathogen Attack. The Plant Cell (2010).
5. Molecular evidence for the involvement of cotton GhGLP2, in enhanced resistance to Verticillium and Fusarium Wilts and oxidative stress. Scientific Reports (2020).
6. Genome-wide identification of germin-like proteins in peanut (Arachis hypogea L.) and expression analysis under different abiotic stresses. Frontiers in Plant Science (2023).
7. Genome-wide analysis of the GLP gene family and overexpression of GLP1-5–1 to promote lignin accumulation during early somatic embryo development in Dimocarpus longan. BMC Genomics (2023).