Variability of gene expression profiles in human blood and lymphoblastoid cell lines

Background

Infection of plants by pathogens and the subsequent disease development involves substantial changes in the biochemistry and physiology of both partners. Analysis of genes that are expressed during these interactions represents a powerful strategy to obtain insights into the molecular events underlying these changes. We have employed expressed sequence tag (EST) analysis to identify rice genes involved in defense responses against infection by the blast fungus Magnaporthe oryzae and fungal genes involved in infectious growth within the host during a compatible interaction.

Results

A cDNA library was constructed with RNA from rice leaves (Oryza sativa cv. Hwacheong) infected with M. oryzae strain KJ201. To enrich for fungal genes, subtraction library using PCR-based suppression subtractive hybridization was constructed with RNA from infected rice leaves as a tester and that from uninfected rice leaves as the driver. A total of 4,148 clones from two libraries were sequenced to generate 2,302 non-redundant ESTs. Of these, 712 and 1,562 ESTs could be identified to encode fungal and rice genes, respectively. To predict gene function, Gene Ontology (GO) analysis was applied, with 31% and 32% of rice and fungal ESTs being assigned to GO terms, respectively. One hundred uniESTs were found to be specific to fungal infection EST. More than 80 full-length fungal cDNA sequences were used to validate ab initio annotated gene model of M. oryzae genome sequence.

Conclusion

This study shows the power of ESTs to refine genome annotation and functional characterization. Results of this work have advanced our understanding of the molecular mechanisms underpinning fungal-plant interactions and formed the basis for new hypothesis.     

The Magnaporthe oryzae Effector AvrPiz-t Targets the RING E3 Ubiquitin Ligase APIP6 to Suppress Pathogen-Associated Molecular Pattern–Triggered Immunity in Rice

Although the functions of a few effector proteins produced by bacterial and oomycete plant pathogens have been elucidated in recent years, information for the vast majority of pathogen effectors is still lacking, particularly for those of plant-pathogenic fungi. Here, we show that the avirulence effector AvrPiz-t from the rice blast fungus Magnaporthe oryzae preferentially accumulates in the specialized structure called the biotrophic interfacial complex and is then translocated into rice (Oryza sativa) cells. Ectopic expression of AvrPiz-t in transgenic rice suppresses the flg22- and chitin-induced generation of reactive oxygen species (ROS) and enhances susceptibility to M. oryzae, indicating that AvrPiz-t functions to suppress pathogen-associated molecular pattern (PAMP)-triggered immunity in rice. Interaction assays show that AvrPiz-t suppresses the ubiquitin ligase activity of the rice RING E3 ubiquitin ligase APIP6 and that, in return, APIP6 ubiquitinates AvrPiz-t in vitro. Interestingly, agroinfection assays reveal that AvrPiz-t and AvrPiz-t Interacting Protein 6 (APIP6) are both degraded when coexpressed in Nicotiana benthamiana. Silencing of APIP6 in transgenic rice leads to a significant reduction of flg22-induced ROS generation, suppression of defense-related gene expression, and enhanced susceptibility of rice plants to M. oryzae. Taken together, our results reveal a mechanism in which a fungal effector targets the host ubiquitin proteasome system for the suppression of PAMP-triggered immunity in plants.     

Exploring the mechanism and efficient use of a durable gene-mediated resistance to bacterial blight disease in rice

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight, the most devastating bacterial disease of rice worldwide. The major disease resistance gene Xa3/Xa26 confers a durable resistance to Xoo with a dosage effect. However, the mechanism of Xa3/Xa26-mediated resistance remains to be elucidated. We created near-isogenic lines carrying Xa3/Xa26 with a background of indica and japonica, the two major subspecies of Asian cultivated rice. Analyzing these rice lines showed that the japonica background facilitated resistance to Xoo, which was associated with increased Xa3/Xa26 expression, compared with rice lines with an indica background. This characteristic of Xa3/Xa26 was related to the WRKY45 locus, which had higher expression with the japonica background than with the indica background. However, the two alleles of the WRKY45 locus had different expression levels, with the WRKY45-1 expression level being higher than that of WRKY45-2 for both japonica and indica backgrounds. In addition, the resistance level conferred by Xa3/Xa26 was higher in the presence of WRKY45-1 than in the presence of WRKY45-2 for both japonica and indica backgrounds. Xa3/Xa26-mediated resistance was associated with increased accumulation of jasmonic acid (JA), JA-isoleucine, and terpenoid and flavonoid phytoalexins. Exogenous JA application enhanced Xa3/Xa26-mediated resistance. These results not only provide more knowledge toward understanding the mechanism of Xa3/Xa26-mediated resistance but also offer the best choice for using Xa3/Xa26 for rice resistance improvement, specifically, a japonica background with the WRKY45-1 allele.     

Quantitative proteomic analyses reveal that RBBI3.3, a trypsin inhibitor protein,plays an important role in <Emphasis Type="Italic">Magnaporthe oryzae</Emphasis> infection in rice

Magnaporthe oryzae (M. oryzae) is the causative agent of rice blast, the most destructive rice disease in China. This study was designed to ascertain the molecular mechanisms of the response of rice to M. oryzae infection to facilitate the breeding of new high-quality and disease-resistant rice varieties using isobaric tags for relative and absolute quantification (iTRAQ) combined with a high-throughput mass spectrometry identification platform. M. oryzae infection models were constructed with the resistant rice cultivar Gumei2 and the non-resistant cultivar Lijiangxintuanheigu (LTH). The results showed that total of 1541 proteins were identified, among which 843 proteins were overlapping between the two biological replicates analyses. Seventy-one proteins were classified as fungi-responsive. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed the important roles of these proteins in metabolic processes. Detailed phenotypic analyses revealed that the trypsin inhibitor RBBI3.3 was effective in inhibiting the initial formation of appressoria. Our quantitative proteomic study provides insights into the molecular mechanism underlying M. oryzae resistance in the incompatible rice Gumei2. The identification of RBBI3.3 as a key defense regulator highlights a new possibility for disease control.