Insect Response to Plant Defensive Protease Inhibitors

Abstract

Plant protease inhibitors (PIs) are natural plant defense proteins that inhibit proteases of invading insect herbivores. However, their anti-insect efficacy is determined not only by their potency toward a vulnerable insect system but also by the response of the insect to such a challenge. Through the long history of coevolution with their host plants, insects have developed sophisticated mechanisms to circumvent antinutritional effects of dietary challenges. Their response takes the form of changes in gene expression and the protein repertoire in cells lining the alimentary tract, the first line of defense. Research in insect digestive proteases has revealed the crucial roles they play in insect adaptation to plant PIs and has brought about a new appreciation of how phytophagous insects employ this group of molecules in both protein digestion and counterdefense. This review provides researchers in related fields an up-to-date summary of recent advances.

Plant Defense Inhibitors Affect the Structures of Midgut Cells in Drosophila melanogaster and Callosobruchus maculatus

“…Insect digestion involves the breakdown of food and absorption of nutrients, processes critical for development and survival 29,30. In the present study, we show that plant defense proteins affect the cellular structure of insect midguts.…”

“…The ultrastructure of midguts of several other insects has been described 27. Various studies have been conducted on the insect larval digestion system and on the effects of lectins on larval development 28,29. However, a more comprehensive understanding of changes in midgut ultrastructure after feeding protease inhibitors, lectins, or αAI is still needed to shed light on the effects of these plant defensive proteins.…”

Review: The future of cystatin engineering

“…Lower potency and poor performance was based on the 5 pest's adaptation to the presence of an exogenous cystatin in transgenic plants and in turn expresses cystatin-insensitive proteases. Insects have developed mechanisms through coevolution, such as changes in gene expression in the gut, to circumvent any anti-digestive effect caused by their plant host [13]. This "weakness" has raised the need to improve the potency of natural cystatins for any realistic inclusion into future biotechnological applications.…”

Drought-stressed tomato plants trigger bottom-up effects on key mite pests

“…Plant-feeding arthropods have developed a remarkable diversity of physiological adaptations to respond to changes in the nutritional composition of their host plants and to counteract the adverse effects of plant defenses including the regulation of digestive and detoxification enzymes (Grbic et al, 2011;Ortego, 2012;Zhu-Salzman, 2015). The hydrolysis of dietary proteins in spider mites relies on cysteine (cathepsin B-, cathepsin L-and legumainlike) and aspartyl (cathepsin D-like) proteases and aminopeptidases (Carrillo et al, 2011;Santamaria et al, 2015a).…”

“…(Zhu-Salzman and Zeng, 2015). Tomato has a large number of PIs: 95 genes were found while only 38 were found on Arabidopsis, being the expression of 25 of them affected by T.…”