Structure, Expression, and Antisense Inhibition of the Systemin Precursor Gene

Abstract

A gene that encodes systemin, a mobile 18-amino acid polypeptide inducer of proteinase inhibitor synthesis in tomato and potato leaves, has been isolated from tomato, Lycopersicon esculentum. Induction of proteinase inhibitors in plants is a response to insect or pathogen attacks. The gene has 10 introns and 11 exons, ten of which are organized as five homologous pairs with an unrelated sequence in the eleventh, encoding systemin. Systemin is proteolytically processed from a 200-amino acid precursor protein, prosystemin. Prosystemin messenger RNA was found in all organs of the plant except the roots and was systemically wound-inducible in leaves. Tomato plants transformed with an antisense prosystemin complementary DNA exhibited greatly suppressed systemic wound induction of proteinase Inhibitor I and II synthesis in leaves.

A Gene Encoding a Chloroplast-Targeted Lipoxygenase in Tomato Leaves Is Transiently Induced by Wounding, Systemin, and Methyl Jasmonate

“…The wound response in tomato was shown previously to be dependent on the synthesis of prosystemin, the polypeptide precursor of systerm'n (McGurl et al, 1992). The prosystemin gene was also shown to be activated by wounding, apparently to amplify the signal during continued herbivore attacks.…”

“…The different timing of the responses indicates that the expression of Tom LoxD, which we term an "early responsive gene, " is first detected within 0.5 h following wounding or elicitation . Other early responsive genes in tomato leaves include prosystemin (McGurl et al, 1992) and allene oxide synthase (G.A. Howe and C.A.…”

“…A phloem mobile polypeptide called systemin behaves as a systemic signal released from wound sites (Pearce et al, 1991;McGurl et al, 1992McGurl et al, , 1994Narvaez-Vasquez et al, 1995), but severa1 other chemicals, including IAA (Thornburg and Li, 1990), ABA (PeAa-Cortés et al, 1989), and ethylene (ODonnell et al, 1996), have been associated with the signaling pathway and with physical forces such as hydraulic effects (Malone and Alarcon, 1995) and action potentials (Herde et al, 1996;Rhodes et al, 1996;Stankovic and Davies, 1996).…”

Gene expression during plant embryogenesis and germination: an overview.

“…So far, stable knockouts of specific genes by homologous recombination, insertional mutagenesis (Meinke, 1991), or site-specific cleavage (Mergny et al, 1992) are problematic. However, antisense (McGurl et al, 1992) and dominant negative (Amaya et al, 1991) knockouts offer attractive alternatives. Overexpression and ectopic expression of wild-type and mutant genes represent another approach.…”

Down-regulation of systemin after herbivory is associated with increased root allocation and competitive ability in Solanum nigrum

“…Systemin has been intensively studied in tomato (Solanum lycopersicum L.) over the past decade and its up-regulation in wounded tomato plants has been shown to lead to TPI production (McGurl et al 1992). Systemin has long been thought to be the mobile wound signal leading to systemic resistance responses, but when wild-type (WT) tomato plants and jasmonic acid (JA) biosynthesis mutants (spr2 mutants) or WT tomato plants and systemin signaling mutants (spr1 mutants) were reciprocally grafted (Howe 2004;Schilmiller and Howe 2005), the role of systemin in the wound response of tomato had to be reconsidered.…”