Maize Endochitinase Expression in Response to Fall Armyworm Herbivory

Abstract

A large percentage of crop loss is due to insect damage yearly, especially caterpillar damage. Plant chitinases are considered excellent candidates to combat these insects since they can catalyze chitin degradation in peritrophic matrix (PM), an important protective structure in caterpillar midgut. Compared to chemical insecticides, chitinases could improve host plant resistance and be both economically and environmentally advantageous. The focus of this research was to find chitinase candidates that could improve plant resistance by effectively limiting caterpillar damage. Five classes of endochitinase (I-V) genes were characterized in the maize genome, and we further isolated and cloned four chitinase genes (chitinase A, chitinase B, chitinase I, and PRm3) present in two maize (Zea mays L.) inbred lines Mp708 and Tx601, with different levels of resistance to caterpillar pests. Further, we investigated the role of these maize chitinases in response to fall armyworm (Spodoptera frugiperda, FAW) attacks. Results from gene expression and enzyme assays from maize leaves indicated that both chitinase transcript abundance and enzymatic activity increased in response to FAW feeding and mechanical wounding. Furthermore, chitinase retained activity inside the caterpillar’s midgut since specific activity was detected in both the food bolus and frass. When examined under scanning electron microscopy, PMs from Tx601-fed caterpillars showed structural damage when compared to diet controls. Analysis of chitinase transcript abundance after caterpillar feeding and proteomic analysis of maize leaf trichomes in the two inbreds suggested that the chitinase PRm3 in Tx601 has potential insecticidal properties.

The Role of Lysobacter antibioticus HS124 on the Control of Fall Webworm (Hyphantria cunea Drury) and Growth Promotion of Canadian Poplar (Populus canadensis Moench) at Saemangeum Reclaimed Land in Korea

“…GH18 chitinase is responsible for chitinase enzyme production, which then degrades chitin into low molecular weight of N-acetylglucosamine such as chitotetraose, chitotriose, and chitobiose [ 27 , 29 ]. This leads to structural disintegration of vital insect organs such as the cuticle [ 28 , 40 ], causing mortality of insect pests due to the hydrolytic activity in the larvae cuticles [ 28 , 41 , 42 ]. In addition, serine proteases have extensive primary specificity for amino acids (e.g., phenylalanine, methionine, and alanine) with a hydrophobic side group in the second carbon atom, but also has a secondary specificity for extended peptide chains with active sites recognizing at least five subsite residues [ 29 ].…”