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Use of a Secretion Trap Screen in Pepper Following Phytophthora capsici Infection Reveals Novel Functions of Secreted Plant Proteins in Modulating Cell Death

June 2011 , Volume 24 , Number  6
Pages  671 - 684

Seon-In Yeom,1 Hyang-Ku Baek,1 Sang-Keun Oh,1 Won-Hee Kang,1 Sang Jik Lee,2 Je Min Lee,1 Eunyoung Seo,1 Jocelyn K. C. Rose,2 Byung-Dong Kim,1 and Doil Choi1

1Department of Plant Science, Plant Genomics and Breeding Institute, Seoul National University, Seoul, 151-921, Republic of Korea; 2Department of Plant Biology, Cornell University, Ithaca, NY 14853, U.S.A.

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Accepted 22 January 2011.

In plants, the primary defense against pathogens is mostly inducible and associated with cell wall modification and defense-related gene expression, including many secreted proteins. To study the role of secreted proteins, a yeast-based signal-sequence trap screening was conducted with the RNA from Phytophthora capsici-inoculated root of Capsicum annuum ‘Criollo de Morelos 334’ (CM334). In total, 101 Capsicum annuum secretome (CaS) clones were isolated and identified, of which 92 were predicted to have a secretory signal sequence at their N-terminus. To identify differences in expressed CaS genes between resistant and susceptible cultivars of pepper, reverse Northern blots and real-time reverse-transcription polymerase chain reaction were performed with RNA samples isolated at different time points following P. capsici inoculation. In an attempt to assign biological functions to CaS genes, we performed in planta knock-down assays using the Tobacco rattle virus-based gene-silencing method. Silencing of eight CaS genes in pepper resulted in suppression of the cell death induced by the non-host bacterial pathogen (Pseudomonas syringae pv. tomato T1). Three CaS genes induced phenotypic abnormalities in silenced plants and one, CaS259 (PR4-l), caused both cell death suppression and perturbed phenotypes. These results provide evidence that the CaS genes may play important roles in pathogen defense as well as developmental processes.

© 2011 The American Phytopathological Society