Gene expression response of Medicago truncatula roots treated with symbiotic lipochitooligosaccharides (LCOs)
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ABSTRACT: Legumes interact with soil microbes, leading to the development of nitrogen-fixing root nodules and arbuscular mycorrhizal (AM) roots. While nodule initiation by diffusible lipochitooligosaccharide (LCO) Nod-factors of bacterial origin (Nod-LCOs) is well characterized, diffusible AM fungal signals were only recently identified as sulphated and non-sulphated LCOs (sMyc-LCOs and nsMyc-LCOs). Applying Myc-LCOs in parallel to Nod-LCOs, we used GeneChips to detail the global programme of gene expression in response to the external application of symbiotic LCOs.
Project description:Legumes interact with soil microbes, leading to the development of nitrogen-fixing root nodules and arbuscular mycorrhizal (AM) roots. While nodule initiation by diffusible lipochitooligosaccharide (LCO) Nod-factors of bacterial origin (Nod-LCOs) is well characterized, diffusible AM fungal signals were only recently identified as sulphated and non-sulphated LCOs (sMyc-LCOs and nsMyc-LCOs). Applying Myc-LCOs in parallel to Nod-LCOs, we used GeneChips to detail the global programme of gene expression in response to the external application of symbiotic LCOs. To harvest tissues for transcriptome profiling, three biological replicates consisting of 20 plantlets per treatment were selected. After 6 h of incubation in the climate chamber, 10 plantlets per batch were removed from the treatment (Myc-LCOs or Nod-LCOs) or control solutions and harvested, while the other 10 remained in the respective solutions for a total of 24 h. During harvest, one mm of the root tip of each plantlet was removed and discarded. The remaining 2 to 2.5 cm of the distal root region were cut off and directly frozen in liquid nitrogen.
Project description:Many plants associate with arbuscular mycorrhizal fungi for nutrient acquisition, while legumes also associate with nitrogen-fixing rhizobial bacteria. Both associations rely on symbiosis signaling and here we show that cereals can perceive lipochitooligosaccharides (LCOs) for activation of symbiosis signaling, surprisingly including Nod factors produced by nitrogen-fixing bacteria. However, legumes show stringent perception of specifically decorated LCOs, that is absent in cereals. LCO perception in plants is activated by nutrient starvation, through transcriptional regulation of Nodulation Signaling Pathway (NSP)1 and NSP2. These transcription factors induce expression of an LCO receptor and act through the control of strigolactone biosynthesis and the karrikin-like receptor DWARF14-LIKE. We conclude that LCO production and perception is coordinately regulated by nutrient starvation to promote engagement with mycorrhizal fungi. Our work has implications for the use of both mycorrhizal and rhizobial associations for sustainable productivity in cereals.
Project description:Legumes interact with soil fungi, leading to the development of arbuscular mycorrhizal (AM) roots. Diffusible AM fungal signals were identified as sulphated and non-sulphated LCOs (sMyc-LCOs and nsMyc-LCOs). Applying Myc-LCOs on roots of symbiotic mutants, we used GeneChips to detail the global programme of gene expression in these mutants in response to the external application of Myc-LCOs.
Project description:Legumes interact with soil fungi, leading to the development of arbuscular mycorrhizal (AM) roots. Diffusible AM fungal signals were identified as sulphated and non-sulphated LCOs (sMyc-LCOs and nsMyc-LCOs). Applying Myc-LCOs on roots of symbiotic mutants, we used GeneChips to detail the global programme of gene expression in these mutants in response to the external application of Myc-LCOs. Keywords: Expression profiling by array
Project description:Legumes interact with rhizobia, leading to the development of root nodules. Diffusible rhizobial signals were identified as Nod-LCOs. Applying Nod-LCOs on plantlet roots, we used GeneChips to detail the global programme of gene expression in response to the external application of Nod-LCOs.
Project description:Legumes interact with soil fungi, leading to the development of arbuscular mycorrhizal (AM) roots. Diffusible AM fungal signals were identified as sulphated and non-sulphated LCOs (sMyc-LCOs and nsMyc-LCOs). Applying Myc-LCOs on roots of symbiotic mutants, we used GeneChips to detail the global programme of gene expression in these mutants in response to the external application of Myc-LCOs. To harvest tissues for transcriptome profiling, three biological replicates consisting of 10 plantlets per treatment were selected. After 6 h of incubation in the climate chamber, 10 plantlets per batch were removed from the treatment (Myc-LCOs) or control solutions and harvested. During harvest, one mm of the root tip of each plantlet was removed and discarded. The remaining 2 to 2.5 cm of the distal root region were cut off and directly frozen in liquid nitrogen.
Project description:Lipo-chitooligosaccharides (LCOs) produced by N2-fixing rhizobacteria initiate host nodule formation. Foliar application of LCOs has been shown to induce stress-related genes under optimal growth conditions. To study the effects of LCO foliar spray under stressed conditions, soybean seedlings grown at optimal temperature were exposed to sub-optimal temperature. After a 5-day acclimation period, the first trifoliolate leaves were sprayed with 10-7 M LCO (NodBj-V (C18:1, MeFuc)) produced by Bradyrhizobium japonicum, and harvested at 0 and 48 h following treatment. Microarray analysis was performed using Affymetrix GeneChip® Soybean Genome Arrays. A total of 147 genes were differentially expressed 48 h after LCO treatment, including a number of stress-related genes and transcription factors. In addition, during the 48 h following treatment, hundreds of genes were differentially expressed in LCO-treated plants, indicating that the dynamic soybean foliar transcriptome was highly responsive to LCO treatment. The microarray data was supported by quantitative real-time PCR data.
Project description:Lipo-chitooligosaccharides (LCOs) produced by N2-fixing rhizobacteria initiate host nodule formation. Foliar application of LCOs has been shown to induce stress-related genes under optimal growth conditions. To study the effects of LCO foliar spray under stressed conditions, soybean seedlings grown at optimal temperature were exposed to sub-optimal temperature. After a 5-day acclimation period, the first trifoliolate leaves were sprayed with 10-7 M LCO (NodBj-V (C18:1, MeFuc)) produced by Bradyrhizobium japonicum, and harvested at 0 and 48 h following treatment. Microarray analysis was performed using Affymetrix GeneChip® Soybean Genome Arrays. A total of 147 genes were differentially expressed 48 h after LCO treatment, including a number of stress-related genes and transcription factors. In addition, during the 48 h following treatment, hundreds of genes were differentially expressed in LCO-treated plants, indicating that the dynamic soybean foliar transcriptome was highly responsive to LCO treatment. The microarray data was supported by quantitative real-time PCR data. Soybean seedlings grown at optimal temperature (25 °C) were exposed to sub-optimal temperature (15 °C). After a 5-day acclimation period, the first trifoliolate leaves were sprayed with 10-7 M LCO (NodBj-V (C18:1, MeFuc)) produced by Bradyrhizobium japonicum, and harvested at 0 and 48 h following treatment. Total RNA was extracted and microarray analysis was performed using Affymetrix GeneChip® Soybean Genome Arrays.
Project description:Legumes grow specialized root nodules that are distinct from lateral roots in morphology and function, with nodules intracellularly hosting beneficial nitrogen-fixing bacteria that provide the plant with nitrogen. We have previously shown that a lateral root-like program underpins nodule initiation, but there must be additional developmental programs that confer nodule identity. Here, we show that two members of the LIGHT SENSITIVE SHORT HYPOCOTYL (LSH) transcription factor family, known to define organ boundaries and meristem complexity in the shoot, function as regulators of nodule organ identity. LSH1/LSH2 function upstream of and together with the known nodule regulators Nuclear Factor Y A1 and NODULE ROOT1/2. The principal outcome of LSH1/LSH2 function is the production of cells able to accommodate nitrogen-fixing bacteria, a unique nodule feature. We conclude that the coordinate recruitment of a pre-existing shoot developmental program, in parallel to a root program, underpins the divergence between lateral roots and nodules.
Project description:Thus, our observations suggested an intriguing possibility that OsCERK1 functions as the receptor of the mycorrhizal signal Myc-LCOs, although the function of Myc-LCOs has been examined only in dicotyledonous plants. To test this hypothesis, we evaluated Myc-LCO responses in rice by transcriptome analysis using next-generation sequencing.