Effect of root colonization by arbuscular mycorrhizal fungi on growth, productivity and blast resistance in rice

Altres ajuts: CERCA Programme/Generalitat de CatalunyaBackground: Arbuscular mycorrhizal (AM) fungi form symbiotic associations with roots in most land plants. AM symbiosis provides benefits to host plants by improving nutrition and fitness. AM symbiosis has also beenassociated with increased resistance to pathogen infection in several plant species. In rice, the effects of AM symbiosis is less studied, probably because rice is mostly cultivated in wetland areas, and plants in such ecosystems have traditionally been considered as non-mycorrhizal. In this study, we investigated the effect of AM inoculation on performance of elite rice cultivars (Oryza sativa, japonica subspecies) under greenhouse and field conditions, focusing on growth, resistance to the rice blast fungus Magnaporthe oryzae and productivity. Results: The response to inoculation with either Funneliformis mosseae or Rhizophagus irregularis was evaluated in a panel of 12 rice cultivars. Root colonization was confirmed in all rice varieties. Under controlled greenhouse conditions, R. irregularis showed higher levels of root colonization than F. mosseae. Compared to non-inoculated plants, the AM-inoculated plants had higher Pi content in leaves. Varietal differences were observed in the growth response of rice cultivars to inoculation with an AM fungus, which were also dependent on the identity of the fungus. Thus, positive, negligible, and negative responses to AM inoculation were observed among rice varieties. Inoculation with F. mosseae or R. irregularis also conferred protection to the rice blast fungus, but the level of mycorrhiza-induced blast resistance varied among host genotypes. Rice seedlings (Loto and Gines varieties) were pre-inoculated with R. irregularis, transplanted into flooded fields, and grown until maturity. A significant increase in grain yield was observed in mycorrhizal plants compared with non-mycorrhizal plants, which was related to an increase in the number of panicles. Conclusion: Results here presented support that rice plants benefit from the AM symbiosis while illustrating the potential of using AM fungi to improve productivity and blast resistance in cultivated rice. Differences observed in the mycorrhizal responsiveness among the different rice cultivars in terms of growth promotion and blast resistance indicate that evaluation of benefits received by the AM symbiosis needs to be carefully evaluated on a case-by-case basis for efficient exploitation of AM fungi in rice cultivation

Phosphate accumulation in rice leaves promotes fungal pathogenicity and represses host immune responses during pathogen infection

Rice is one of the most important crops in the world and a staple food for more than half of the world’s population. At present, the blast disease caused by the fungus Magnaporthe oryzae poses a severe threat to food security through reduction of rice yields worldwide. High phosphate fertilization has previously been shown to increase blast susceptibility. At present, however, our knowledge on the mechanisms underpinning phosphate-induced susceptibility to M. oryzae infection in rice is limited. In this work, we conducted live cell imaging on rice sheaths inoculated with a M. oryzae strain expressing two fluorescently-tagged M. oryzae effectors. We show that growing rice under high phosphate fertilization, and subsequent accumulation of phosphate in leaf sheaths, promotes invasive growth of M. oryzae. Consistent with this, stronger expression of M. oryzae effectors and Pathogenicity Mitogen-activated Protein Kinase (PMK1) occurs in leaf sheaths of rice plants grown under high a phosphate regime. Down-regulation of fungal genes encoding suppressors of plant cell death and up-regulation of plant cell death-inducing effectors also occurs in sheaths of phosphate over-accumulating rice plants. Treatment with high Pi causes alterations in the expression of fungal phosphate transporter genes potentially contributing to pathogen virulence. From the perspective of the plant, Pi accumulation in leaf sheaths prevents H2O2 accumulation early during M. oryzae infection which was associated to a weaker activation of Respiratory Burst Oxidase Homologs (RBOHs) genes involved in reactive oxygen species (ROS) production. Further, a weaker activation of defense-related genes occurs during infection in rice plants over-accumulating phosphate. From these results, it can be concluded that phosphate fertilization has an effect on the two interacting partners, pathogen and host. Phosphate-mediated stimulation of fungal effector genes (e.g., potentiation of fungal pathogenicity) in combination with repression of pathogen-inducible immune responses (e.g., ROS accumulation, defense gene expression) explains higher colonization by M. oryzae in rice tissues accumulating phosphate. Phosphate content can therefore be considered as an important factor in determining the outcome of the rice/M. oryzae interaction. As fertilizers and pesticides are commonly used in rice cultivation to maintain optimal yield and to prevent losses caused by pathogens, a better understanding of how phosphate impacts blast susceptibility is crucial for developing strategies to rationally optimize fertilizer and pesticide use in rice production

Integrative approach for precise genotyping and transcriptomics of a salt tolerant introgression line in rice

Trabajo presentado al 18th International Symposium on Rice Functional Genomics (ISRFG), celebrado en Barcelona del 3 al 5 de noviembre de 2021.Peer reviewe

Data_Sheet_2_Integrative Approach for Precise Genotyping and Transcriptomics of Salt Tolerant Introgression Rice Lines.docx

3 pages. -- Supplementary Methods: Transcriptome analysis by RNA-Seq and identification of introgressed indica regionsRice is the most salt sensitive cereal crop and its cultivation is particularly threatened by salt stress, which is currently worsened due to climate change. This study reports the development of salt tolerant introgression lines (ILs) derived from crosses between the salt tolerant indica rice variety FL478, which harbors the Saltol quantitative trait loci (QTL), and the salt-sensitive japonica elite cultivar OLESA. Genotyping-by-sequencing (GBS) and Kompetitive allele specific PCR (KASPar) genotyping, in combination with step-wise phenotypic selection in hydroponic culture, were used for the identification of salt-tolerant ILs. Transcriptome-based genotyping allowed the fine mapping of indica genetic introgressions in the best performing IL (IL22). A total of 1,595 genes were identified in indica regions of IL22, which mainly located in large introgressions at Chromosomes 1 and 3. In addition to OsHKT1;5, an important number of genes were identified in the introgressed indica segments of IL22 whose expression was confirmed [e.g., genes involved in ion transport, callose synthesis, transcriptional regulation of gene expression, hormone signaling and reactive oxygen species (ROS) accumulation]. These genes might well contribute to salt stress tolerance in IL22 plants. Furthermore, comparative transcript profiling revealed that indica introgressions caused important alterations in the background gene expression of IL22 plants (japonica cultivar) compared with its salt-sensitive parent, both under non-stress and salt-stress conditions. In response to salt treatment, only 8.6% of the salt-responsive genes were found to be commonly up- or down-regulated in IL22 and OLESA plants, supporting massive transcriptional reprogramming of gene expression caused by indica introgressions into the recipient genome. Interactions among indica and japonica genes might provide novel regulatory networks contributing to salt stress tolerance in introgression rice lines. Collectively, this study illustrates the usefulness of transcriptomics in the characterization of new rice lines obtained in breeding programs in rice.Peer reviewe

Data_Sheet_1_Integrative Approach for Precise Genotyping and Transcriptomics of Salt Tolerant Introgression Rice Lines.PDF

13 pages. -- Supplementary Figure 1. Breeding scheme used in the marked-assisted backcross introgression of the Saltol QTL from FL478 (indica) into the background of the rice variety OLESA (temperate japonica rice). -- Supplementary Figure 2. Polymorphism obtained with the SKC10 SSR marker visualized by agarose gel analysis. (A) Saltol QTL region showing the SKC10 SSR marker and relevant salt-related genes positions. (B) PCR products obtained from the Saltol donor (FL478), the recurrent (OLESA) parent and 4 representative introgression lines derived from FL478 x OLESA crosses (BC2F1). C-, negative control, He, heterozygous, Ho, homozygous. Primers are indicated in Supplementary Table 2. -- Supplementary Figure 3. Graphical representation of the genotypes of the Saltol-introgressed rice lines (BC3F3). Genotyping was carried out by KASPar analysis. SNPs are indicated in columns according to their chromosomal location (in mega base-pairs, Mb). Introgression lines (IL1 to IL31) are clustered in four groups (I to IV) depending on the BC3F1 parent from which they derive. The Saltol QTL location (and length) is indicated in the upper part. Homozygous donor (FL478) and recurrent (OLESA) alleles are depicted in blue and white, respectively. The KASPar markers used in this study are listed in Supplementary Tables 1 and 2. -- Supplementary Figure 4. SES score of parental lines (FL478, OLESA) hydroponically grown in modified Yoshida solution containing different NaCl concentrations (60 mM, 80 mM and 100 mM) for 14 days. Box plots show the distribution of SES scores in each line and condition (15 plants/genotype each experiment; T-test, * P < 0.05). Values above each box indicate the mean SES score . -- Supplementary Figure 5. Characterization of salt tolerant introgression lines. (A) Standard evaluation system (SES) scores of visual salt injury of the 30 ILs. Evaluation was performed after 14 days of salt treatment (80 mM NaCl). SES scores are shown as the percentage of plants at each score value. 1, highly tolerant; 3, tolerant; 5, moderately tolerant; 7, sensitive; 9, highly sensitive. ILs are clustered in four groups (I to IV) depending on the BC3F1 parent used. ILs were evaluated in successive rounds, with 5 plants and 10 plants in control and salt conditions respectively in each experiment, and most salt-sensitive ILs were discarded in the following assays. A total of six independent experiments were carried out with the most salt-tolerant ILs. (B) Representative images of IL22 and IL13 plants and parental lines in control and salt conditions after 14 days of treatment. -- Supplementary Figure 6. Plant growth of parental lines (FL478, OLESA) and IL22 plants hydroponically grown in modified Yoshida solution containing 80 mM NaCl. Control plants were not supplemented with NaCl. The leaf number of each genotype at different times of salt treatment is indicated. At least 6 plants per genotype and condition were assayed. -- Supplementary Figure 7. Samples analysed by RNASeq, and comparisons of data sets from each genotype (IL22, OLESA) and condition (control, salt-treated). -- Supplementary Figure 8. Singular enrichment analysis of introgressed indica genes (chromosome 1, blocks 1 and 2, and chromosome 3) using AgriGO (Tian et al., 2017). For a full list of gene IDs, see Supplementary Table 5. -- Supplementary Figure 9. Singular enrichment analysis of japonica genes up-regulated in IL22 plants at 24 h of salt treatment (80 mM NaCl) using AgriGO (Tian et al., 2017). For a full list of gene IDs, see Supplementary Table 8. -- Supplementary Figure 10. Singular enrichment analysis of japonica genes up-regulated in OLESA plants at 24 h of salt treatment (80 mM NaCl) using AgriGO (Tian et al., 2017). For a full list of gene IDs, see Supplementary Table 8. -- Supplementary Figure 11. Singular enrichment analysis of japonica genes down-regulated in IL22 plants at 24 h of salt treatment (80 mM NaCl) using AgriGO (Tian et al., 2017). For a full list of gene IDs, see Supplementary Table 8. -- Supplementary Figure 12. Singular enrichment analysis of japonica genes down-regulated in OLESA plants at 24 h of salt treatment (80 mM NaCl) using AgriGO (Tian et al., 2017). For a full list of gene IDs, see Supplementary Table 8. -- Supplementary Figure 13. Mapman analysis of japonica genes up- and down-regulated in IL22 and OLESA plants at 24 h of salt treatment (80 mM NaCl). Regulation overview, stress and transport schemes are shown. Color scale (yellow to blue) represents the log2 fold change of salt vs. control conditions.Rice is the most salt sensitive cereal crop and its cultivation is particularly threatened by salt stress, which is currently worsened due to climate change. This study reports the development of salt tolerant introgression lines (ILs) derived from crosses between the salt tolerant indica rice variety FL478, which harbors the Saltol quantitative trait loci (QTL), and the salt-sensitive japonica elite cultivar OLESA. Genotyping-by-sequencing (GBS) and Kompetitive allele specific PCR (KASPar) genotyping, in combination with step-wise phenotypic selection in hydroponic culture, were used for the identification of salt-tolerant ILs. Transcriptome-based genotyping allowed the fine mapping of indica genetic introgressions in the best performing IL (IL22). A total of 1,595 genes were identified in indica regions of IL22, which mainly located in large introgressions at Chromosomes 1 and 3. In addition to OsHKT1;5, an important number of genes were identified in the introgressed indica segments of IL22 whose expression was confirmed [e.g., genes involved in ion transport, callose synthesis, transcriptional regulation of gene expression, hormone signaling and reactive oxygen species (ROS) accumulation]. These genes might well contribute to salt stress tolerance in IL22 plants. Furthermore, comparative transcript profiling revealed that indica introgressions caused important alterations in the background gene expression of IL22 plants (japonica cultivar) compared with its salt-sensitive parent, both under non-stress and salt-stress conditions. In response to salt treatment, only 8.6% of the salt-responsive genes were found to be commonly up- or down-regulated in IL22 and OLESA plants, supporting massive transcriptional reprogramming of gene expression caused by indica introgressions into the recipient genome. Interactions among indica and japonica genes might provide novel regulatory networks contributing to salt stress tolerance in introgression rice lines. Collectively, this study illustrates the usefulness of transcriptomics in the characterization of new rice lines obtained in breeding programs in rice.Peer reviewe

A Novel Semi-Supervised Methodology for Extracting Tumor Type-Specific MRS Sources in Human Brain Data

BackgroundThe clinical investigation of human brain tumors often starts with a non-invasive imaging study, providing information about the tumor extent and location, but little insight into the biochemistry of the analyzed tissue. Magnetic Resonance Spectroscopy can complement imaging by supplying a metabolic fingerprint of the tissue. This study analyzes single-voxel magnetic resonance spectra, which represent signal information in the frequency domain. Given that a single voxel may contain a heterogeneous mix of tissues, signal source identification is a relevant challenge for the problem of tumor type classification from the spectroscopic signal.Methodology/Principal FindingsNon-negative matrix factorization techniques have recently shown their potential for the identification of meaningful sources from brain tissue spectroscopy data. In this study, we use a convex variant of these methods that is capable of handling negatively-valued data and generating sources that can be interpreted as tumor class prototypes. A novel approach to convex non-negative matrix factorization is proposed, in which prior knowledge about class information is utilized in model optimization. Class-specific information is integrated into this semi-supervised process by setting the metric of a latent variable space where the matrix factorization is carried out. The reported experimental study comprises 196 cases from different tumor types drawn from two international, multi-center databases. The results indicate that the proposed approach outperforms a purely unsupervised process by achieving near perfect correlation of the extracted sources with the mean spectra of the tumor types. It also improves tissue type classification.Conclusions/SignificanceWe show that source extraction by unsupervised matrix factorization benefits from the integration of the available class information, so operating in a semi-supervised learning manner, for discriminative source identification and brain tumor labeling from single-voxel spectroscopy data. We are confident that the proposed methodology has wider applicability for biomedical signal processing

Jardins per a la salut

Facultat de Farmàcia, Universitat de Barcelona. Ensenyament: Grau de Farmàcia. Assignatura: Botànica farmacèutica. Curs: 2014-2015. Coordinadors: Joan Simon, Cèsar Blanché i Maria Bosch.Els materials que aquí es presenten són el recull de les fitxes botàniques de 128 espècies presents en el Jardí Ferran Soldevila de l’Edifici Històric de la UB. Els treballs han estat realitzats manera individual per part dels estudiants dels grups M-3 i T-1 de l’assignatura Botànica Farmacèutica durant els mesos de febrer a maig del curs 2014-15 com a resultat final del Projecte d’Innovació Docent «Jardins per a la salut: aprenentatge servei a Botànica farmacèutica» (codi 2014PID-UB/054). Tots els treballs s’han dut a terme a través de la plataforma de GoogleDocs i han estat tutoritzats pels professors de l’assignatura. L’objectiu principal de l’activitat ha estat fomentar l’aprenentatge autònom i col·laboratiu en Botànica farmacèutica. També s’ha pretès motivar els estudiants a través del retorn de part del seu esforç a la societat a través d’una experiència d’Aprenentatge-Servei, deixant disponible finalment el treball dels estudiants per a poder ser consultable a través d’una Web pública amb la possibilitat de poder-ho fer in-situ en el propi jardí mitjançant codis QR amb un smartphone

Role of phosphate in the regulation of immune responses

Trabajo presentado en el Stress Seminar del Centre de Recerca Agrigenómica (CRAG), celebrado el 9 de febrero de 2021.Peer reviewe

Mechanisms underlying phosphate-induced susceptibility to the rice blast fungus Magnaporthe oryzae

Trabajo presentado al 18th International Symposium on Rice Functional Genomics (ISRFG), celebrado on-line del 3 al 5 de noviembre de 2021.Peer reviewe

Mechanisms of phosphate-induced susceptibility to the blast fungus in rice: Regulation of plant defense gene expression and fungal pathogenicity

Trabajo presentado en el XVI Meeting of Plant Molecular Biology, celebrado en Sevilla entre el 14 y el 16 de septiembre de 2022.Rice blast caused by the fungus Magnaporthe oryzae is the most devastating fungal disease of rice worldwide. To reduce losses due to M. oryzae infection, and to obtain maximum yields, high amounts of pesticides and fertilizers continue to be applied in rice cultivation causing an adverse impact on human health and environment. It is also known that nutrition might have an impact on disease severity and, in some cases, excess of fertilization might have negative efects on disease resistance. Although adaptation to nutrient supply conditions and immunity are not independent processes, the molecular mechanisms involved in nutrient stress responses and innate immunity have been so far investigated separately from each other. In this study, we investigated the efect of phosphate (Pi) supply on resistance to infection by the blast fungus M. oryzae in rice, focusing on the two partners of the interaction. On the plant side, we found that high Pi fertilization, and subsequent Pi accumulation, enhances blast susceptibility which is associated to a weaker activation of defense related genes during M. oryzae infection. Regarding the pathogen, confocal microscopy of rice sheaths inoculated with a M. oryzae strain co-expressing two genes encoding fuorescently-labeled efectors (PWL2 and BAS4) revealed early induction of M. oryzae efectors in rice plants that have been grown under high Pi supply. Overall, these results support that Pi accumulation has an efect on the two partners of the interaction, host and pathogen, by undermining host defense programmes and stimulating fungal pathogenicity. Cross-talk between the two signalling pathways, Pi signalling and immune signalling, would then play an essential role in controlling blast susceptibility in rice. These fndings illustrate the fact that the indiscriminate use of Pi fertilizers might have adverse efects on the rice plant by increasing the likelihood of blast disease. A better understanding of the interconnected regulations between nutrient (Pi) supply and disease resistance will lay a foundation for rationally optimizing fertilizer and pesticide use in rice production