Tomato Pathogenesis-related Protein Genes are Expressed in Response to Trialeurodes vaporariorum and Bemisia tabaci Biotype B Feeding

The temporal and spatial expression of tomato wound- and defense-response genes to Bemisia tabaci biotype B (the silverleaf whitefly) and Trialeurodes vaporariorum (the greenhouse whitefly) feeding were characterized. Both species of whiteflies evoked similar changes in tomato gene expression. The levels of RNAs for the methyl jasmonic acid (MeJA)- or ethylene-regulated genes that encode the basic β-1,3-glucanase (GluB), basic chitinase (Chi9), and Pathogenesis-related protein-1 (PR-1) were monitored. GluB and Chi9 RNAs were abundant in infested leaves from the time nymphs initiated feeding (day 5). In addition, GluB RNAs accumulated in apical non-infested leaves. PR-1 RNAs also accumulated after whitefly feeding. In contrast, the ethylene- and salicylic acid (SA)-regulated Chi3 and PR-4 genes had RNAs that accumulated at low levels and GluAC RNAs that were undetectable in whitefly-infested tomato leaves. The changes in Phenylalanine ammonia lyase5 (PAL5) were variable; in some, but not all infestations, PAL5 RNAs increased in response to whitefly feeding. PAL5 RNA levels increased in response to MeJA, ethylene, and abscisic acid, and declined in response to SA. Transcripts from the wound-response genes, leucine aminopeptidase (LapA1) and proteinase inhibitor 2 (pin2), were not detected following whitefly feeding. Furthermore, whitefly infestation of transgenic LapA1:GUS tomato plants showed that whitefly feeding did not activate the LapA1 promoter, although crushing of the leaf lamina increased GUS activity up to 40 fold. These studies indicate that tomato plants perceive B. tabaci and T. vaporariorum in a manner similar to baterical pathogens and distinct from tissue-damaging insects

Generation of systemin signaling in tobacco by transformation with the tomato systemin receptor kinase gene

The tomato systemin receptor, SR160, a plasma membrane-bound, leucine-rich repeat receptor kinase that signals systemic plant defense, and the brassinolide (BL) receptor, BRI1, that regulates developmental processes, have been shown recently to have identical amino acid sequences. We report herein that tobacco, a solanaceous species that does not express a systemin precursor gene nor responds to systemin, when transformed with the SR160 receptor gene, expresses the gene in suspension-cultured cells, evidenced by mRNA and protein analyses and photoaffinity-labeling experiments. Additionally, systemin induced an alkalinization response in the transgenic tobacco cells similar to that found in tomato cells, but not in WT cells. The gain in function in tobacco cells indicates that early steps of the systemin signaling pathway found in tomato are present in tobacco cells. A tomato line, cu-3, in which a mutation in the BRI1 gene has rendered the plant nonfunctional in BL signaling, exhibits a severely reduced response to systemin. In leaves of WT tomato plants, BL strongly and reversibly antagonized systemic signaling by systemin. The results suggest that the systemin-mediated systemic defense response may have evolved in some solanaceous species by co-opting the BRI1 receptor and associated components for defense signaling