Project description:Phytophthora root and stem rot caused by the oomycete pathogen Phytophthora sojae, is one of the most destructive diseases of soybean. Deploying soybean cultivars carrying race-specific resistance conferred by Rps genes is the most practicalapproach to managing this disease. Previously, two Rps genes, RpsUN1 and RpsUN2 conferring broad spectra of resistance to P. sojae isolates, were identified in a landrace PI 567139B and mapped to a 6.5-cM region on chromosome 3 and a 3.0-cM region on chromosome 16, corresponding to 840 kb and 600 kb of sequences, respectively,of the soybean reference genome. By analyzing ten and nine recombinants defined by genotypic and phenotypic screening of the 826 F2:3 families derived from two reciprocal crosses between the two parental lines of the mapping populations, RpsUN1 and RpsUN2 were further narrowed to a 151-kb region that harbors five genes including three NBS-LRR genes, and a 36-kb region that contains four genes including five NBS-LRR genes, respectively, according to the reference genome. Analysis of expressional changes of these nine genes before and after inoculation with the pathogen suggest that the counterparts of Glyma.03g034600 in the RpsUN1 region and the counterparts of Glyma.16g215200 and Glyma.16g214900 in the RpsUN2 region of PI 567139B may be associated with the resistance to P. sojae. It is also suggested that unequal recombination between different NBS-LRR genes in the mapped regions may have occurred, resulting in the formation of two recombinants with inconsistent genotypes and phenotypes detected by molecular markers within the fine-mapped regions. The haplotypes of genomic regions surrounding RpsUN1 and RpsUN2 in the entire soybean germplasm deposited in the US soybean germplasm collection were analyzed towards a better understanding of the origins of these two novel sources of resistance and screening of effective markers for marker-assisted selectionof these two resistance genes for soybean breeding.

Project description:To gain novel molecular insights into quantitative late blight resistance, we performed a high-resolution quantitative analysis of gene expression using potato cultivars with contrasting SNP alleles at the StAOS2 locus associated with maturity corrected resistance (MCR). SuperSAGE samples were generated from uninfected and infected plants of the selected genotypes under controlled environmental conditions. Genotypes were pooled to reduce the influence of the genetic background on the transcriptome. Nine SuperSAGE samples were prepared from artificially inoculated plants in a growth chamber using total RNA of the pooled 14, 6 and 9 genotypes in groups A1, A2 and B2, respectively, at three infection time points T0, T1 and T2. Combining the tag counts of both NlaIII and DpnII libraries resulted in 1.1 to 6.2 million tags per sample. Of total 266361 unique tags (unitags), 52.6% matched to the potato genome sequence when up to three mismatches per 26 base pairs were allowed, and 23.3% matched without mismatch. Fifteen pair wise comparisons were performed between the nine SuperSAGE samples to identify transcripts that were differentially expressed in response to infection (six comparisons) or between three genotype pools at the infection time points T0, T1 and T2 (nine comparisons). The number of unitags per comparison ranged from 127 000 to 182 000 (average 158 000). Between 2100 and 11800 tags were differentially expressed in pair wise comparisons, depending on arbitrary cut-off p-values for a significant difference. The highest number of differences was observed for the comparison between genotype pools A1 and A2 one day after infection (A1-T1 vs A2-T1), and the lowest between genotype pools A2 and B2 two days after infection (B2-T2 vs A2-T2). The number of differences in response to infection and between genotype pools even before infection (T0) was in the same order of magnitude. Based on the annotations in the DFCI potato gene index, in the potato genome and in few cases by BLASTX searches against the protein database at NCBI, transcripts that showed reproducible differential expression over the infection time course or between genotype pools A1, A2 and B2 were grouped in 16 functional categories, with overlaps between categories. Genes with genotype dependent, constitutive differential expression provide excellent targets for developing novel diagnostic markers for breeding cultivars with improved quantitative resistance to late blight and possibly other biotic and abiotic stresses. Relevant in this respect appear, besides numerous genes of unknown or ill-defined function, genes with known function involved in stress responses, photosynthesis, protein biosynthesis, protein degradation via the 26S proteasome, transport of proteins, lipids, ions and other small molecules, cell wall structure and many others.

Project description:To gain novel molecular insights into quantitative late blight resistance, we performed a high-resolution quantitative analysis of gene expression using potato cultivars with contrasting SNP alleles at the StAOS2 locus associated with maturity corrected resistance (MCR). SuperSAGE samples were generated from uninfected and infected plants of the selected genotypes under controlled environmental conditions. Genotypes were pooled to reduce the influence of the genetic background on the transcriptome. Nine SuperSAGE samples were prepared from artificially inoculated plants in a growth chamber using total RNA of the pooled 14, 6 and 9 genotypes in groups A1, A2 and B2, respectively, at three infection time points T0, T1 and T2. Combining the tag counts of both NlaIII and DpnII libraries resulted in 1.1 to 6.2 million tags per sample. Of total 266361 unique tags (unitags), 52.6% matched to the potato genome sequence when up to three mismatches per 26 base pairs were allowed, and 23.3% matched without mismatch. Fifteen pair wise comparisons were performed between the nine SuperSAGE samples to identify transcripts that were differentially expressed in response to infection (six comparisons) or between three genotype pools at the infection time points T0, T1 and T2 (nine comparisons). The number of unitags per comparison ranged from 127 000 to 182 000 (average 158 000). Between 2100 and 11800 tags were differentially expressed in pair wise comparisons, depending on arbitrary cut-off p-values for a significant difference. The highest number of differences was observed for the comparison between genotype pools A1 and A2 one day after infection (A1-T1 vs A2-T1), and the lowest between genotype pools A2 and B2 two days after infection (B2-T2 vs A2-T2). The number of differences in response to infection and between genotype pools even before infection (T0) was in the same order of magnitude. Based on the annotations in the DFCI potato gene index, in the potato genome and in few cases by BLASTX searches against the protein database at NCBI, transcripts that showed reproducible differential expression over the infection time course or between genotype pools A1, A2 and B2 were grouped in 16 functional categories, with overlaps between categories. Genes with genotype dependent, constitutive differential expression provide excellent targets for developing novel diagnostic markers for breeding cultivars with improved quantitative resistance to late blight and possibly other biotic and abiotic stresses. Relevant in this respect appear, besides numerous genes of unknown or ill-defined function, genes with known function involved in stress responses, photosynthesis, protein biosynthesis, protein degradation via the 26S proteasome, transport of proteins, lipids, ions and other small molecules, cell wall structure and many others. Eighteen SuperSAGE libraries were constructed based on nine leaf samples from one infection experiment. For each time point (T0, T1 and T2) one leaflet each of 14, 6 and 9 SL genotypes in genotypic groups A1, A2 and B2, respectively, were pooled. Frozen pooled leaf tissue was powdered in a CryoMill. SuperSAGE libraries were generated at GenXPro GmbH (Frankfurt, Germany) essentially as described (Matsumura et al. 2010). To prevent amplification biases the TrueQuant technology was applied as described by B. Rotter (Patent application Nr. WO2009152928). Besides NlaIII (recognition site: 5M-bM-^@M-^Y-CATG-3M-bM-^@M-^Y), DpnII (recognition site: 5M-bM-^@M-^Y-GATC-3M-bM-^@M-^Y) was used as second anchoring enzyme, to capture transcripts without a NlaIII site. Therefore, the 26 bp tags carry either CATG or GATC at their 5M-bM-^@M-^Y end. The libraries were pooled and sequenced by Solexa/Illumina technology (Illumina, Inc., USA).

Project description:Phytophthora root and stem rot caused by the oomycete pathogen Phytophthora sojae is a destructive disease of soybean worldwide. Plant dirigent proteins (DIR) are proposed to have roles in biosynthesis of either lignan or lignin-like molecules, and are important for defense responses, secondary metabolism, and pathogen resistance. In the present work, a novel DIR gene expressed sequence tag is identified as up-regulated in the highly resistant soybean cultivar 'Suinong 10' inoculated with P. sojae. The full length cDNA is isolated using rapid amplification of cDNA ends, and designated GmDIR22 (GenBank accession no. HQ_993047). The full length GmDIR22 is 789 bp and contains a 567 bp open reading frame encoding a polypeptide of 188 amino acids. The sequence analysis indicated that GmDIR22 contains a conserved dirigent domain at amino acid residues 43-187. The quantitative real-time reverse transcription PCR demonstrated that soybean GmDIR22 mRNA is expressed most highly in stems, followed by roots and leaves. The treatments with stresses demonstrated that GmDIR22 is significantly induced by P. sojae and gibberellic acid (GA3), and also responds to salicylic acid, methyl jasmonic acid, and abscisic acid. The GmDIR22 is targeted to the cytomembrane when transiently expressed in Arabidopsis protoplasts. Moreover, The GmDIR22 recombinant protein purified from Escherichia coli could effectively direct E-coniferyl alcohol coupling into lignan (+)-pinoresinol. Accordingly, the overexpression of GmDIR22 in transgenic soybean increased total lignan accumulation. Moreover, the lignan extracts from GmDIR22 transgenic plants effectively inhibits P. sojae hyphal growth. Furthermore, the transgenic overexpression of GmDIR22 in the susceptible soybean cultivar 'Dongnong 50' enhances its resistance to P. sojae. Collectively, these data suggested that the primary role of GmDIR22 is probably involved in the regulation of lignan biosynthesis, and which contributes to resistance to P. sojae.

Dataset Information

Identification and candidate gene analysis of a novel phytophthora resistance gene Rps10 in a Chinese soybean cultivar.

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Identification and candidate gene analysis of a novel phytophthora resistance gene Rps10 in a Chinese soybean cultivar.

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