Project description:Rice blast disease is a major threat to rice production worldwide, but the mechanisms underlying rice resistance to the causal agent Magnaporthe oryzae remain elusive. In this whole-genome transcriptome study of rice early defense response to M. oryzae, we applied Affymetrix Rice Genome Genechip to compare the compatible and incompatible rice-M. oryzae interactions in 24 hours post-inoculation.
Project description:Reliably generating rice varieties with low glycemic index (GI) is an important nutritional intervention given the high rates of Type II diabetes incidences in Asia where rice is staple diet. We integrated a genome-wide association study (GWAS) with a transcriptome-wide association study (TWAS) to determine the genetic basis of the GI in rice. GWAS utilized 305 re-sequenced diverse indica panel comprising ~2.4 million single nucleotide polymorphisms (SNPs) enriched in genic regions. A novel association signal was detected at a synonymous SNP in exon 2 of LOC_Os05g03600 for intermediate-to-high GI phenotypic variation. Another major hotspot region was predicted for contributing intermediate-to-high GI variation, involves 26 genes on chromosome 6 (GI6.1). These set of genes included GBSSI, two hydrolase genes, genes involved in signalling and chromatin modification. The TWAS and methylome sequencing data revealed cis-acting functionally relevant genetic variants with differential methylation patterns in the hot spot GI6.1 region, narrowing the target to 13 genes. Conversely, the promoter region of GBSSI and its alternative splicing allele (G allele of Wxa) explained the intermediate-to-high GI variation. A SNP (C>T) at exon-10 was also highlighted in the preceding analyses to influence final viscosity (FV), which is independent of amylose content/GI. The low GI line with GC haplotype confirmed soft texture, while other two low GI lines with GT haplotype were characterized as hard and cohesive. The low GI lines were further confirmed through clinical in vivo studies. Gene regulatory network analysis highlighted the role of the non‑starch polysaccharide pathway in lowering GI.
Project description:BackgroundBakanae disease, caused by seed-borne Fusarium species, mainly F. fujikuroi, is a rice disease whose importance is considerably increasing in several rice growing countries, leading to incremental production losses.ResultsA germplasm collection of japonica rice was screened for F. fujikuroi resistance, allowing the identification of accessions with high-to-moderate levels of resistance to bakanae. A GWAS approach uncovered two genomic regions highly associated with the observed phenotypic variation for response to bakanae infection on the short arm of chromosome 1 (named as qBK1_628091) and on the long arm of chromosome 4 (named as qBK4_31750955). High levels of phenotypic resistance to bakanae were associated to the cumulated presence of the resistant alleles at the two resistance loci, suggesting that they can provide useful levels of disease protection in resistance breeding. A fine comparison with the genomic positions of qBK1_628091 and qBK4_31750955 with respect to the QTLs for bakanae resistance reported in the literature suggests that the resistant loci here described represent new genomic regions associated to F. fujikuroi resistance. A search for candidate genes with a putative role in bakanae resistance was conducted considering all the annotated genes and F. fujikuroi-related DEGs included in the two genomic regions highlighting several gene functions that could be involved in resistance, thus paving the way to the functional characterization of the resistance loci.ConclusionsNew effective sources for bakanae resistance were identified on rice chromosomes 1 and 4 and tools for resistance breeding are provided.
Project description:In rice, a number of resistance (R) genes that counter the blast fungus, Magnaporthe oryzae, have been cloned, but the mechanism by which they trigger disease resistance remains elusive. This is in part due to a lack of comprehensive transcriptome analyses during the resistance or disease progression. Here, we monitored the gene expression profiling in rice during its interactions with Magnaporthe by time-series transcriptome analyses. Distinct from previous studies, we focused on early infection stages within 24 hours post-inoculation. A comparison of those expression changes revealed a general difference in gene expression kinetics between compatible and incompatible interactions, and pointed to that the time when the pathogen just establishes its penetration into rice cells is a key point for the expressional changes. Such conclusions originated from the R gene Pid3-mediated immune responses were validated in the R gene Pi9-mediated responses, suggesting common molecular processes are shared by different R-mediated blast immunity. Our data highlighted the role of jasmonic acid (JA)-triggered signaling pathway (JA pathway) in the hormone signaling network for rice blast resistance. We confirmed that both exogenous and endogenous JA can induce the expression of many defense-related components revealed in above transcriptomic analyses and proved that the knock-down of OsCOI1 which encodes a JA receptor may deprive rice of the blast resistance mediated by R genes. Therefore, it is concluded that JA pathway plays an essential role in the establishment of blast resistance by modulating the expression of other defense-related components.