Protease Inhibition Mechanisms in Plant-Insect Interactions

Plants deploy a sophisticated arsenal of protease inhibitors to thwart insect herbivores that rely on digestive proteases to extract nutrients from foliage. These inhibitors, often categorised by their target enzyme class – serine, cysteine or aspartic proteases – may be constitutively expressed or induced in response to feeding damage. By binding to the active site of insect gut proteases such as trypsin and chymotrypsin, plant inhibitors disrupt protein digestion, leading to reduced larval growth, delayed development and, in some cases, mortality. In turn, insects exhibit remarkable digestive plasticity, expressing alternative protease isoforms or upregulating inhibitor‐insensitive enzymes to overcome plant defences. At the molecular level, families such as the Kunitz and Bowman-Birk inhibitors present conserved reactive loops that fit into protease catalytic pockets, while phytocystatins target cysteine proteases through a wedge-shaped motif. The co-evolutionary dynamics underpin broad-spectrum resistance traits and inform strategies for enhancing crop protection. Advances in structural biology, peptide engineering and transgenic expression underpin the design of next-generation biopesticides and resistant cultivars, offering global applications in sustainable agriculture.

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Protease Inhibition Mechanisms in Plant-Insect Interactions publication trend

The graph below shows the total number of articles in protease inhibition mechanisms in plant-insect interactions across all publications each year (not limited to Nature Index journals).

Technical terms

Protease inhibitor: A proteinaceous molecule that binds to a protease’s active site or exosite, blocking substrate access and preventing protein degradation.

Serine protease: A class of proteolytic enzymes featuring a serine residue in the active site that participates in peptide bond hydrolysis.

Cysteine protease: An enzyme that uses a catalytic cysteine thiol to cleave peptide bonds, often targeted by phytocystatins.

Kunitz inhibitor: A ~20 kDa family of plant protease inhibitors characterised by a conserved reactive loop and disulfide-stabilised fold, primarily targeting serine proteases.

Phytocystatin: A plant-derived cysteine protease inhibitor with a wedge-shaped consensus motif that binds and blocks the active site of insect and pathogen cysteine proteases.

References

1. A constitutive serine protease inhibitor suppresses herbivore performance in tea (Camellia sinensis). Horticulture Research (2023).
2. Arabidopsis Kunitz Trypsin Inhibitors in Defense Against Spider Mites. Frontiers in Plant Science (2018).
3. Phytocystatins: Defense Proteins against Phytophagous Insects and Acari. International Journal of Molecular Sciences (2016).