Project description:Root exudates contain specialised metabolites that affect the plant’s root microbiome. How host-specific microbes cope with these bioactive compounds, and how this ability shapes root microbiomes, remains largely unknown. We investigated how maize root bacteria metabolise benzoxazinoids, the main specialised metabolites of maize. Diverse and abundant bacteria metabolised the major compound in the maize rhizosphere MBOA and formed AMPO. AMPO forming bacteria are enriched in the rhizosphere of benzoxazinoid-producing maize and can use MBOA as carbon source. We identified a novel gene cluster associated with AMPO formation in microbacteria. The first gene in this cluster, bxdA encodes a lactonase that converts MBOA to AMPO in vitro. A deletion mutant of the homologous bxdA genes in the genus Sphingobium, does not form AMPO nor is it able to use MBOA as a carbon source. BxdA was identified in different genera of maize root bacteria. Here we show that plant-specialised metabolites select for metabolisation-competent root bacteria. BxdA represents a novel benzoxazinoid metabolisation gene whose carriers successfully colonize the maize rhizosphere and thereby shape the plant’s chemical environmental footprint
Project description:The goal of this study was to optimize protein extraction methods to study root-associated bacteria in maize. For this we inoculated sterile maize plants with a synthetic community composed of seven different bacteria (Ben Niu et al. PNAS 2017, vol 114, n 12). Then, we extracted proteins from maize roots using eight different protein extraction methods in triplicates. These methods were a combination of different extraction buffers (SDS or Triton-based) and mechanical disruption methods (bead-beating, N2 grinding, glass homogenizer and freeze-thaw cycles). We found that vortexing maize roots with glass beads in PBS yielded the highest numbers of microbial protein identification.
Project description:Low phosphate concentrations are frequently a constraint for maize growth and development, and therefore, enormous quantities of phosphate fertilizer are expended in maize cultivation, which increases the cost of planting. Low phosphate stress not only increases root biomass but can also cause significant changes in root morphology. Low phosphate availability has been found to favor lateral root growth over primary root growth by dramatically reducing primary root length and increasing lateral root elongation and lateral root density in Arabdopsis. While in our assay when inbred line Q319 subjected to phosphate starvation, The numbers of lateral roots and lateral root primordia were decreased after 6 days of culture in a low phosphate solution (LP) compared to plants grown under normal conditions (sufficient phosphate, SP), and these differences were increased associated with the stress caused by phosphate starvation. However, the growth of primary roots appeared not to be sensitive to low phosphate levels. This is very different to Arabidopsis. To elucidate how low phosphate levels regulate root modifications, especially lateral root development, a transcriptomic analysis of the 1.0-1.5 cm lateral root primordium zone (LRZ) of maize Q319 treated after 2 and 8 days by low phosphate was completed respectively. The present work utilized an Arizona Maize Oligonucleotide array 46K version slides, which contained 46,000 maize 70-mer oligonucleotides designated by TIGR ID, and the sequence information is available at the website of the Maize Oligonucleotide Array Project as the search item representing the >30,000 identifiable unique maize genes (details at http://www.maizearray.org). Keywords: low phosphate, Lateral Root Primordium Zone, maize
Project description:In maize, nitrate regulates root development thanks to the coordinated action of many players. In this study, the involvement of SLs and auxin as putative downstream components of the nitrate regulation of lateral root development was investigated. To this aim, the endogenous SL content of maize root in response to nitrate availability was assessed by means of LC-MS/MS and measurements of lateral root density in the presence of analogues or inhibitors of auxin and strigolactones were performed. Furthermore, un untargeted RNA-seq based approach was used to better characterize the participation of auxin and strigolacotones to the transcriptional signature of maize root response to nitrate. Our results suggested that N deprivation toughly induces zealactone and carlactonoic acid biosynthesis in maize root, to a higher extent if compared to P-deprived roots. Moreover, data on lateral root density led to hypothesise the existence of both auxin-dependent and auxin-independent effects of nitrate on LR development. In addition, the inhibition of SL biosynthesis seems to participate to the auxin-dependent induction of LR, but the involvement of further downstream unknown components cannot be ruled out.
Project description:Low phosphate concentrations are frequently a constraint for maize growth and development, and therefore, enormous quantities of phosphate fertilizer are expended in maize cultivation, which increases the cost of planting. Low phosphate stress not only increases root biomass but can also cause significant changes in root morphology. Low phosphate availability has been found to favor lateral root growth over primary root growth by dramatically reducing primary root length and increasing lateral root elongation and lateral root density in Arabdopsis. While in our assay when inbred line Q319 subjected to phosphate starvation, The numbers of lateral roots and lateral root primordia were decreased after 6 days of culture in a low phosphate solution (LP) compared to plants grown under normal conditions (sufficient phosphate, SP), and these differences were increased associated with the stress caused by phosphate starvation. However, the growth of primary roots appeared not to be sensitive to low phosphate levels. This is very different to Arabidopsis. To elucidate how low phosphate levels regulate root modifications, especially lateral root development, a transcriptomic analysis of the 1.0-1.5 cm lateral root primordium zone (LRZ) of maize Q319 treated after 2 and 8 days by low phosphate was completed respectively. The present work utilized an Arizona Maize Oligonucleotide array 46K version slides, which contained 46,000 maize 70-mer oligonucleotides designated by TIGR ID, and the sequence information is available at the website of the Maize Oligonucleotide Array Project as the search item representing the >30,000 identifiable unique maize genes (details at http://www.maizearray.org). Keywords: low phosphate, Lateral Root Primordium Zone, maize Two-condition experiment, low phosphate treated lateral root primordium zone of maize root vs. normal cultrued lateral root primordium zone. Biological replicates: 9 control, 9 treated, independently grown and harvested. One replicate per array.
Project description:The association between soil microbes and plant roots is present in all natural and agricultural environments. Microbes can be beneficial, pathogenic, or neutral to the host plant development and adaptation to abiotic or biotic stresses. Progress in investigating the functions and changes in microbial communities in diverse environments have been rapidly developing in recent years, but the changes in root function is still largely understudied. The aim of this study was to determine how soil bacteria influence maize root transcription and microRNAs (miRNAs) populations in a controlled inoculation of known microbes over a defined time course. At each time point after inoculation of the maize inbred line B73 with ten bacterial isolates, DNA and RNA were isolated from roots. The V4 region of the 16S rRNA gene was amplified from the DNA and sequenced with the Illumina MiSeq platform. Amplicon sequencing of the 16S rRNA gene indicated that most of the microbes successfully colonized maize roots. The colonization was dynamic over time and varied with the specific bacterial isolate. Small RNA sequencing and mRNA-Seq was done to capture changes in the root transcriptome from 0.5 to 480 hours after inoculation. The transcriptome and small RNA analyses revealed epigenetic and transcriptional changes in roots due to the microbial inoculation. This research provides the foundational data needed to understand how plant roots interact with bacterial partners and will be used to develop predictive models for root response to bacteria.
Project description:We investigated root hair-specific transcriptome using RNA-seq in maize. ZmLRL5 was further identified as a key regulator of maize root hair elongation.
Project description:Herbaspirillum seropedicae is an endophytic bacterium that can fix nitrogen and promote a hormonal imbalance that leads to a plant growth-promoting effect when used as a microbial inoculant. Studies focused on mechanisms of action are crucial for a better understanding of the bacteria-plant interaction and optimization of plant growth-promoting response. The work aims to understand the underlined mechanisms responsible for the early stimulatory growth effects of the H. seropedicae inoculation in maize. To perform it, we combined transcriptomic and proteomic approaches with physiological analysis. The results obtained with the inoculation showed increased root biomass (233 and 253%) and shoot biomass (249 and 264%), respectively, for the fresh and dry mass of maize seedlings and increased green content and development. Omics data analysis for the positive biostimulation phenotype revealed that inoculation increases N-uptake and N-assimilation machinery through differential expressed nitrate transporters and amino acids pathway, as well carbon/nitrogen metabolism integration by the tricarboxylic acid cycle and the polyamines pathway. Additionally, phytohormone levels of root and shoot tissues increased in bacterium-inoculated-maize plants leading to feedback regulation by the ubiquitin-proteasome system. The early biostimulatory effect of H. seropedicae partially results from hormonal imbalance coupled with efficient nutrient uptake-assimilation and a boost in primary anabolic metabolism of carbon-nitrogen integrative pathways.