Figure 1.
Physical map of the P. sojae Avr3a and Avr5 region.
Shown are the positions of predicted genes including candidate RXLR effector genes, and synteny with P. ramorum. In P. sojae strain P6497, Avr3a is embedded in a 10.8 kb DNA segment that is present in a tandem array of four copies, which is shown as a box in this illustration (not drawn to scale). Scaffold designations are from v1.0 of the genome sequence.
Table 1.
Summary of Avr5 candidate genes in P.sojae strains P6497 and P70641.
Figure 2.
Predicted amino acid sequences of Avr3a alleles from three strains of P. sojae.
The position of the predicted signal peptide and the RXLR and EER host-targeting sequences are shown. The deduced Avr3a protein sequence in P. sojae strains P6497 and ACR12 differs by two amino acids, as indicted by the asterisks. The Avr3a genes from strains P6497 and ACR12 are transcribed whereas no transcripts can be detected for Avr3a from P7064.
Table 2.
Virulence phenotypes and haplotype analysis of P. sojae strains.
Figure 3.
Expression of Avr3aP6497 in Rps5 soybean plants can trigger cell death.
Results from a co-bombardment assay are shown. The ratio of GUS-positive blue spots following co-bombardment with Avr3aP6497, Avr3aP7064 and Avr3aACR12 compared with the empty vector DNA. Expression constructs for Avr3a alleles were without signal peptides. Soybean lines Williams (rps) and L85–3059 (Rps5) are genetic isolines. Bars represent standard errors from 12–14 replicates each. An asterisk (*) indicates a significant difference (p<0.001) by the Wilcoxon rank sum test.
Figure 4.
Expression levels of Avr3a in wild-type and transgenic strains of P. sojae.
(A) Relative expression of Avr3a in mycelia cultures of wild-type strains P6497 and P7074, and transgenic over-expressing strains P7074:Avr3aP6497-O3, P7074:Avr3aP6497-O4, and P7074:Avr3aP6497-O8. Expression was measured by quantitative real time PCR and normalized to the level in wild-type P6497. (B) Relative expression of Avr3a in mycelia cultures of wild-type strains P6497 and P7074, and transgenic silenced strain P6497:Avr3aP6497-S1. Expression was measured by quantitative real time PCR and normalized to the level in wild-type P6497. Bars indicate standard errors from three independent replicates.
Figure 5.
Disease lesion lengths in etiolated soybean hypocotyls infected with zoospores of wild-type and Avr3a transformed strains of P. sojae, 36 h after inoculation.
Mean and standard error from at least 20 measurements are shown in each case, with results from Duncan's multiple range test (1% significance) indicated above each column. (A) Ectopic over-expression of Avr3aP6497 causes loss of virulence to Rps3a and Rps5 in strain P7074. Shown are results from wild-type strains P6497 and P7074, and transgenic over-expressing strains P7074:Avr3aP6497-O3, P7074:Avr3aP6497-O4, and P7074:Avr3aP6497-O8. (B) Silencing of Avr3aP6497 causes gain of specific virulence in the presence of Rps3a and Rps5 in strain P6497. Shown are results from wild-type strains P6497 and P7074, and transgenic silenced strain P6497:Avr3aP6497-S1.
Table 3.
Virulence characteristics of P. sojae wild-type strains P6497 and P7074 and Avr3a-transformed strains.
Table 4.
Virulence phenotypes in the presence of Rps3a and Rps5 of P. sojae field isolates, from three different studies.