Proteomics study of changes in soybean lines resistant and sensitive to Phytophthora sojae

Abstract

Background: Phytophthora sojae causes soybean root and stem rot, resulting in an annual loss of 1-2 billion US dollars in soybean production worldwide. A proteomic technique was used to determine the effects on soybean hypocotyls of infection with P. sojae.

Results: In the present study, 46 differentially expressed proteins were identified in soybean hypocotyls infected with P. sojae, using two-dimensional electrophoresis and matrix-assisted laser desorption/ionization tandem time of flight (MALDI-TOF/TOF). The expression levels of 26 proteins were significantly affected at various time points in the tolerant soybean line, Yudou25, (12 up-regulated and 14 down-regulated). In contrast, in the sensitive soybean line, NG6255, only 20 proteins were significantly affected (11 up-regulated and 9 down-regulated). Among these proteins, 26% were related to energy regulation, 15% to protein destination and storage, 11% to defense against disease, 11% to metabolism, 9% to protein synthesis, 4% to secondary metabolism, and 24% were of unknown function.

Conclusion: Our study provides important information on the use of proteomic methods for studying protein regulation during plant-oomycete interactions.

Figure 1

Symptoms of soybeans 12, 24, and 48 h post-inoculation using the hypocotyl inoculation method. A, B, and C show symptoms in NG6255. D, E, and F show symptoms in Yudou25. G, H, I, and J show close-up views of NG6255 (G, H) and Yudou25 (I, J) 24 and 48 h after inoculation.

Figure 2

Representative gel maps of Yudou25. CK and T stand for mock- and PNJ1-inoculated soybean. Different inoculation times are shown on the bottom. The 2-DE was performed using 240 μg of protein, linear 17 cm IPG strips (pH 4-7), and 12% SDS-PAGE gels for second electrophoresis. Gels were stained with silver nitrate.

Figure 3

Representative gel maps of NG6255. CK and T stand for mock- and PNJ1-inoculated soybean. Different inoculation times are shown on the bottom. The 2-DE was performed using 240 μg of protein, linear 17 cm IPG strips (pH 4-7), and 12% SDS-PAGE gels for second electrophoresis. Gels were stained with silver nitrate.

Figure 4

Identification of 26 and 20 protein spots from Yudou25 (A) and NG6255 (B), respectively. The numbers with arrows indicate the differentially expressed protein spots. pI and Mr are shown on the gels.

Figure 5

Distribution of identified protein classes in Yudou25 and NG6255 using the methods of Bevan et al. [27]. The percentages of the same functional class accounting for all the identified proteins from Yudou25 and NG6255 are represented in white and black, respectively.