systemin and Disease-Resistance

Plant defense responses against invading organisms are initiated through the perception of molecules associated with attacking microbes and herbivores by pattern recognition receptors. In addition to elicitor molecules derived from attacking organisms, plants recognize host-derived molecules. These endogenous elicitors induce and amplify the defense responses against invading organisms both locally and systemically. Several classes of plant-derived molecules elicit defense, including cell wall fragments and peptides. Endogenous peptide elicitors have been discovered in species across the plant kingdom, and their role regulating immunity to both herbivores and pathogens is becoming increasingly appreciated. In this review, we will focus on the five known endogenous peptide elicitor families, summarize their properties, and discuss research goals to further understanding of plant innate immunity.

Topics: Antimicrobial Cationic Peptides; Calcium; Disease Resistance; Peptides; Plant Immunity; Plant Proteins; Plants; Protease Inhibitors; Protein Binding; Reactive Oxygen Species; Receptors, Pattern Recognition; Signal Transduction

Systemin (SYS), an octadecapeptide hormone processed from a 200-amino-acid precursor (prosystemin, PS), plays a central role in the systemic activation of defense genes in tomato in response to herbivore and pathogen attacks. However, whether PS mRNA is transferable and its role in systemic defense responses remain unknown. We created the transgenic tomato PS gene tagged with the green fluorescent protein (PS-GFP) using a shoot- or root-specific promoter, and the constitutive 35S promoter in Arabidopsis. Subcellular localization of PS-/SYS-GFP was observed using confocal laser scanning microscopy and gene transcripts were determined using quantitative real-time PCR. In Arabidopsis, PS protein can be processed and SYS is secreted. Shoot-/root-specific expression of PS-GFP in Arabidopsis, and grafting experiments, revealed that the PS mRNA moves in a bi-directional manner. We also found that ectopic expression of PS improves Arabidopsis resistance to the necrotrophic fungus Botrytis cinerea, consistent with substantial upregulation of the transcript levels of specific pathogen-responsive genes. Our results provide novel insights into the multifaceted mechanism of SYS signaling transport and its potential application in genetic engineering for increasing pathogen resistance across diverse plant families.

Topics: Arabidopsis; Botrytis; Disease Resistance; Fluorescence; Gene Expression Regulation, Plant; Green Fluorescent Proteins; Peptides; Plant Diseases; Plant Proteins; Plant Roots; Plant Shoots; Plants, Genetically Modified; Proteolysis; RNA Transport; RNA, Messenger; Seedlings; Solanum lycopersicum; Subcellular Fractions