Submitted to: Planta
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/15/2010
Publication Date: 8/14/2010
Publication URL: hdl.handle.net/10113/47304
Citation: Soria-Guerra, R.E., Rosales-Mendoza, S., Chang, S., Haudenshield, J.S., Zheng, D., Rao, S.S., Hartman, G.L., Ghabrial, S.A., Korban, S.S. 2010. Identifying differentially expressed genes in leaves of Glycine tomentella in the presence of the fungal pathogen Phakopsora pachyrhizi. Planta. 232:1181-1189. Interpretive Summary: Soybean rust (SBR), caused by the fungus Phakopsora pachyrhizi, is a serious disease of soybean causing crop losses in many parts of the world. P. pachyrhizi first was identified in soybean in the USA in 2004. Soybean cultivars grown in the USA have not been bred for rust resistance. Identifying sources of genetic resistance to SBR in soybean (G. max) has yielded some promising results; however, there has not been any source of resistance identified that has not been overcome by a pathotype or race of P. pachyrhizi. Sources of SBR resistance have been identified in the wild perennial species Glycine tomentella. To rapidly identify genes for resistance, the approach of suppression subtractive hybridization was used to isolate plant genes involved in resistance responses. Thus, efforts have been underway to identify sources of genetic resistance to SBR resistance genes in soybean relatives for potential transfer into commercial soybean cultivars. Using this approach, several genes that are constitutively expressed at high levels in the resistant genotype, but transcribed only at low levels in the susceptible genotype were identified. A number of these genes have been found to encode products belonging to groups of defense-related proteins. This information is useful to plant scientists working in the field of molecular plant engineering.
Technical Abstract: Transcription profiles of Glycine tomentella genotypes having different responses to soybean rust, caused by the fungal pathogen Phakopsora pachyrhizi, were compared using suppression subtractive hybridization (SSH). Four cDNA libraries were constructed from infected and non-infected leaves of resistant (PI509501) and susceptible (PI441011) genotypes of G. tomentella, and subjected to subtractive hybridization. A total of 1536 sequences were obtained from these cDNA libraries; 1060 transcripts were identified. Of these sequenced cDNA clones, predicted functions for 646 clones (61%) were assigned. In addition, proteins encoded by 160 clones (15%) had significant sequence similarity to hypothetical proteins; while, the remaining 254 clones (24%) did not reveal any hits. The differential expression of the clones was confirmed by real time RT-PCR. Of those 646 clones with known functions, different genes encoding protein products involved in metabolism, cell defense, energy, protein synthesis, transcription, and cellular transport were identified. Thus, these cDNA libraries were useful in identifying resistant genes to P. pachyrhizi infection.