To understand the transcriptional regulatory mechanism of host genes during the activation of defense responses in rice, we isolated WRKY transcription factors whose expressions were altered upon attack of the fungal pathogen Magnaporthe grisea, the causal agent of the devastating rice blast disease. A systematic expression analysis of OsWRKYs (Oryza sativa L. WRKYs) revealed that among 45 tested genes the expression of 15 genes was increased remarkably in an incompatible interaction between rice and M. grisea. Twelve of the M. grisea-inducible OsWRKY genes were also differentially regulated in rice plants infected with the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). In experiments with defense signaling molecules, the expression of two genes, OsWRKY45 and OsWRKY62, was increased in salicylic acid (SA)-treated leaves and the expression of three genes, OsWRKY10, OsWRKY82, and OsWRKY85 was increased by jasmonic acid (JA) treatment. OsWRKY30 and OsWRKY83 responded to both SA- and JA treatments. The expression profiles suggest that a large number of WRKY DNA-binding proteins are involved in the transcriptional activation of defense-related genes in response to rice pathogens.

Resveratrol has been clinically shown to possess a number of human health benefits. As a result, many attempts have been made to engineer resveratrol production in major cereal grains but have been largely unsuccessful. In this study, we report the creation of a transgenic rice plant that accumulates 1.9 µg resveratrol/g in its grain, surpassing the previously reported anti-metabolic syndrome activity of resveratrol through a synergistic interaction between the transgenic resveratrol and the endogenous properties of the rice. Consumption of our transgenic resveratrol-enriched rice significantly improved all aspects of metabolic syndrome and related diseases in animals fed a high-fat diet. Compared with the control animals, the resveratrol-enriched rice reduced body weight, blood glucose, triglycerides, total cholesterol, and LDL-cholesterol by 24.7%, 22%, 37.4%, 27%, and 59.6%, respectively. The resveratrol-enriched rice from our study may thus provide a safe and convenient means of preventing metabolic syndrome and related diseases without major lifestyle changes or the need for daily medications. These results also suggest that future transgenic plants could be improved if the synergistic interactions of the transgene with endogenous traits of the plant are considered in the experimental design.

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To identify genes involved in rice Pi5-mediated disease resistance to Magnaporthe oryzae, we compared the proteomes of the RIL260 rice strain carrying the Pi5 resistance gene with its susceptible mutants M5465 and M7023. Proteins were extracted from the leaf tissues of both RIL260 and the mutant lines at 0, 24, and 48 h after M. oryzae inoculation and separated by two-dimensional polyacrylamide gel electrophoresis (2-DE). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis identified eight proteins that were differently expressed between the resistant and susceptible plants (three down-and five up-regulated proteins in the mutants). The down-regulated proteins included a triosephosphate isomerase (spot no. 2210), a 2,3-bisphosphoglycerate-independent phosphoglycerate mutase (no. 3611), and an unknown protein (no. 4505). In addition, the five up-regulated proteins in the mutants were predicted to be a fructokinase I (no. 313), a glutathione S-transferase (no. 2310), an atpB of chloroplast ATP synthase (no. 3616), an aminopeptidase N (no. 3724), and an unknown protein (no. 308). These results suggest that proteomic analysis of rice susceptible mutants is a useful method for identifying novel proteins involved in resistance to the M. oryzae pathogen.

The required for Mla12 resistance (RAR1) protein is essential for the plant immune response. In rice, a model monocot species, the function of Oryza sativa RAR1 (OsRAR1) has been little explored. In our current study, we characterized the response of a rice osrar1 T-DNA insertion mutant to infection by Magnaporthe oryzae, the causal agent of rice blast disease. osrar1 mutants displayed reduced resistance compared with wild type rice when inoculated with the normally virulent M. oryzae isolate PO6-6, indicating that OsRAR1 is required for an immune response to this pathogen. We also investigated the function of Os-RAR1 in the resistance mechanism mediated by the immune receptor genes Pib and Pi5 that encode nucleotide binding-leucine rich repeat (NB-LRR) proteins. We inoculated progeny from Pib/osrar1 and Pi5/osrar1 heterozygous plants with the avirulent M. oryzae isolates, race 007 and PO6-6, respectively. We found that only Pib-mediated resistance was compromised by the osrar1 mutation and that the introduction of the OsRAR1 cDNA into Pib/osrar1 rescued Pib-mediated resistance. These results indicate that OsRAR1 is required for Pib-mediated resistance but not Pi5-mediated resistance to M. oryzae.