Accumulation of a maize proteinase inhibitor in response to wounding and insect feeding, and characterization of its activity toward digestive proteinases of Spodoptera littoralis larvae

Abstract

The mpi gene encodes a maize proteinase inhibitor (MPI) protein whose mRNA accumulates in response to mechanical wounding. In this study, mpi gene expression in response to different types of damage was investigated. In mechanically damaged leaves of maize (Zea mays L.), mpi mRNA accumulation was affected by the degree of damage inflicted on the leaf. Consecutive wounds resulted in higher levels of mpi transcripts. The MPI protein was expressed in Escherichia coli and purified. Polyclonal antibodies were then produced and used to study MPI accumulation in insect-wounded and mechanically wounded maize leaves. When larvae of the lepidopteran insect Spodoptera littoralis were fed on maize leaves, MPI accumulated in tissues adjacent to the wound site. The level of inhibitor accumulation was higher in leaves chewed by larvae than in leaves that had been damaged mechanically. Longer feeding periods also resulted in higher levels of MPI accumulation. Additionally, the inhibitory properties of MPI toward mammalian and insect digestive serine proteinases were determined. Contrary to the majority of the plant proteinase inhibitors described, MPI is an inhibitor of mammalian elastase that only weakly inhibits mammalian chymotrypsin. However, both elastase and chymotrypsin-like activities from the larval midgut of S. littoralis were effectively inhibited by MPI. We discuss these results with regard to the function and evolution of plant proteinase inhibitors. The availability of a plant proteinase inhibitor which is able to inhibit the two types of insect digestive proteinase, elastase and chymotrypsin, might be useful for engineering protection against lepidopteran insect pests in transgenic plants.

Disruption of OPR7 and OPR8 Reveals the Versatile Functions of Jasmonic Acid in Maize Development and Defense

“…This selection included the entire gene families of maize LOX (see Supplemental Table 1 online), OPR (Zhang et al, 2005), and JAZ genes (maize JAZs, see Supplemental Table 1 online; Arabidopsis JAZs, Yan et al, 2007). We also selected other defense genes of interest, including MPI (Tamayo et al, 2000), the ethylene biosynthesis genes ACS2, ACS6, and ACS7 (Young et al, 2004), the insect defense gene Mir1 (Ankala et al, 2009), the defensin gene PDC (Kant et al, 2009), and the anthocyanin biosynthesis genes A1, A2, C2, BZ1, and BZ2 (see Supplemental Table 1 online). The macroarray profile revealed that 67 of this 85-gene set, including LOX7/8, LOX9, AOS1, OPR7/8, MYC2, JAZ7, JAZ8, and MYC2, etc., were upregulated 1 and 2 h Table 1 online) in response to wounding of opr7-5 opr8-2 and wild-type plants.…”

A Plasma Membrane Protein from Zea mays Binds with the Herbivore Elicitor Volicitin

“…Certain of these defenses, such as toxic alkaloids, terpenoids, and phenolics, are expressed constitutively (Wittstock and Gershenzon, 2002), whereas others such as proteinase inhibitors (Tamayo et al, 2000) and polyphenol oxidases (Constabel et al, 1995) are not normally triggered unless the plant is damaged. Although these latter defense responses are known to be wound inducible, there are numerous studies showing that injury by insects can result in augmented or attenuated physiological and biochemical plant responses compared with mechanical damage alone.…”

Biotechnological Approaches for the Control of Insect Pests in Crop Plants

“…Plants protect themselves directly by constitutively expressing protease inhibitors [170] and by inducing protease inhibitors in response to mechanical wounding or insect attack [169,171]. They may also release volatile compounds after insect damage that function as potent attractants for predators of insect herbivores [172]. The release of volatile compounds after wounding, such as methyl jasmonate also triggers the production of proteinase inhibitors in neighbouring unwounded plants essentially prearming the local population against insect attack [173].…”