Redundancy in Plant Defense Figure 8. Morphology, cell death, SA/SAG levels. PR-1 and R gene expression ssi2 eds1-2 pad4-1 and ssi2 eds1-2 eds5-1 plants. (A) Comparison of the morphological phenotypes displayed by 4-week-old soil-grown wt (SSI2), ssi2, ssi2 eds1, ssi2 pad4, ssi2 eds5, ssi2 eds1 pad4, and ssi2 eds1 eds5 plants. (B) Microscopy of trypan blue-stained leaves from indicated genotypes. (C) Expression of PR-1 gene in indicated genotypes. Total RNA was extracted from 4-week-old plants and used for RNA gel-blot analysis. Ethidium bromide staining of rRNA was used as the loading control. (D) Endogenous SA levels in the leaves of 4-week-old soil-grown plants. Values are presented as mean of three replicates and the error bars represent SD. Statistical significance was determined using Students t-test. Asterisks indicate data statistically significant compared to SSI2 (Col-0) plants (P,0.05, n = 5). (E) Endogenous SAG levels in the leaves of 4-week-old soil-grown plants. Values are presented as mean of three replicates and the error bars represent SD. Asterisks indicate data statistically significant compared to SSI2 (Col-0) plants (P,0.05, n = 5). (F) RT–PCR analysis of R genes in indicated genotypes. The level of b-tubulin was used as an internal control to normalize the amount of cDNA template. The SSI2 EDS1, SSI2 PAD4, SSI2 EDS1 PAD4, and SSI2 EDS1 EDS5 F2 plants showed wt–like morphology, accumulated basal levels of SA and showed basal level expression of PR-1 and R genes (data not shown). doi:10.1371/journal.pgen.1000545.g008 PLoS Genetics | www.plosgenetics.org 12 July 2009 | Volume 5 | Issue 7 | e1000545