School of BioSciences - Research Publications
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ItemPlant Growth Promotion and Heat Stress Amelioration in Arabidopsis Inoculated with Paraburkholderia phytofirmans PsJN Rhizobacteria Quantified with the GrowScreen-Agar II Phenotyping Platform(MDPI, 2022-11)High temperatures inhibit plant growth. A proposed strategy for improving plant productivity under elevated temperatures is the use of plant growth-promoting rhizobacteria (PGPR). While the effects of PGPR on plant shoots have been extensively explored, roots-particularly their spatial and temporal dynamics-have been hard to study, due to their below-ground nature. Here, we characterized the time- and tissue-specific morphological changes in bacterized plants using a novel non-invasive high-resolution plant phenotyping and imaging platform-GrowScreen-Agar II. The platform uses custom-made agar plates, which allow air exchange to occur with the agar medium and enable the shoot to grow outside the compartment. The platform provides light protection to the roots, the exposure of it to the shoots, and the non-invasive phenotyping of both organs. Arabidopsis thaliana, co-cultivated with Paraburkholderia phytofirmans PsJN at elevated and ambient temperatures, showed increased lengths, growth rates, and numbers of roots. However, the magnitude and direction of the growth promotion varied depending on root type, timing, and temperature. The root length and distribution per depth and according to time was also influenced by bacterization and the temperature. The shoot biomass increased at the later stages under ambient temperature in the bacterized plants. The study offers insights into the timing of the tissue-specific, PsJN-induced morphological changes and should facilitate future molecular and biochemical studies on plant-microbe-environment interactions.
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ItemRoot Growth and Architecture of Wheat and Brachypodium Vary in Response to Algal Fertilizer in Soil and Solution(MDPI, 2022-02)Alternative, recycled sources for mined phosphorus (P) fertilizers are needed to sustain future crop growth. Quantification of phenotypic adaptations and performance of plants with a recycled nutrient source is required to identify breeding targets and agronomy practices for new fertilization strategies. In this study, we tested the phenotypic responses of wheat (Triticum aestivum) and its genetic model, Brachypodium (Brachypodium distachyon), to dried algal biomass (with algae or high or low mineral P) under three growing conditions (fabricated ecosystems (EcoFABs), hydroponics, and sand). For both species, algal-grown plants had similar shoot biomass to mineral-grown plants, taking up more P than the low mineral P plants. Root phenotypes however were strongly influenced by nutrient form, especially in soilless conditions. Algae promoted the development of shorter and thicker roots, notably first and second order lateral roots. Root hairs were 21% shorter in Brachypodium, but 24% longer in wheat with algae compared to mineral high P. Our results are encouraging to new recycled fertilization strategies, showing algae is a nutrient source to wheat and Brachypodium. Variation in root phenotypes showed algal biomass is sensed by roots and is taken up at a higher amount per root length than mineral P. These phenotypes can be selected and further adapted in phenotype-based breeding for future renewal agriculture systems.
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ItemModulators or facilitators? Roles of lipids in plant root-microbe interactions(CELL PRESS, 2022-02)Lipids have diverse functions in regulating the plasma membrane's cellular processes and signaling mediation. Plasma membrane lipids are also involved in the plant's complex interactions with the surrounding microorganisms, with which plants are in various forms of symbiosis. The roles of lipids influence the whole microbial colonization process, thus shaping the rhizomicrobiome. As chemical signals, lipids facilitate the stages of rhizospheric interactions - from plant root to microbe, microbe to microbe, and microbe to plant root - and modulate the plant's defense responses upon perception or contact with either beneficial or phytopathogenic microorganisms. Although studies have come a long way, further investigation is needed to discover more lipid species and elucidate novel lipid functions and profiles under various stages of plant root-microbe interactions.
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ItemThe Metabolic Response of Brachypodium Roots to the Interaction with Beneficial Bacteria Is Affected by the Plant Nutritional Status(MDPI, 2021-06)The potential of plant growth promoting (PGP) bacteria in improving the performance of plants in suboptimal environments is increasingly acknowledged, but little information is available on the mechanisms underlying this interaction, particularly when plants are subjected to a combination of stresses. In this study, we investigated the effects of the inoculation with the PGP bacteria Azospirillum brasilense (Azospirillum) on the metabolism of the model cereal Brachypodium distachyon (Brachypodium) grown at low temperatures and supplied with insufficient phosphorus. Investigating polar metabolite and lipid fluctuations during early plant development, we found that the bacteria initially elicited a defense response in Brachypodium roots, while at later stages Azospirillum reduced the stress caused by phosphorus deficiency and improved root development of inoculated plants, particularly by stimulating the growth of branch roots. We propose that the interaction of the plant with Azospirillum was influenced by its nutritional status: bacteria were sensed as pathogens while plants were still phosphorus sufficient, but the interaction became increasingly beneficial for the plants as their phosphorus levels decreased. Our results provide new insights on the dynamics of the cereal-PGP bacteria interaction, and contribute to our understanding of the role of beneficial microorganisms in the growth of cereal crops in suboptimal environments.
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ItemWheat Can Access Phosphorus From Algal Biomass as Quickly and Continuously as From Mineral Fertilizer(FRONTIERS MEDIA SA, 2021-01-28)Algae can efficiently take up excess nutrients from waterways, making them a valuable resource potentially capable of replacing synthesized and mined fertilizers for agriculture. The capacity of algae to fertilize crops has been quantified, but it is not known how the algae-derived nutrients become available to plants. We aimed to address this question: what are the temporal dynamics of plant growth responses to algal biomass? to better propose mechanisms by which plants acquire nutrients from algal biomass and thereby study and promote those processes in future agricultural applications. Data from various sources were transformed and used to reconstruct the nutrient release from the algae Chlorella vulgaris and subsequent uptake by wheat (Triticum aestivum L.) (as reported in Schreiber et al., 2018). Plants had received 0.1x or 1x dried algae or wet algae, or zero, 0.1x or 1x mineral fertilizer calculated from agricultural practices for P application and grown to 55 days in three soils. Contents of P and other nutrients acquired from algae were as high as from mineral fertilizer, but varied based on moisture content and amount of algae applied to soils (by 55 days after sowing plants with 1x mineral fertilizer and 1x dried algae had 5.6 mg P g DWshoot; 2.2-fold more than those with 0 or 0.1x mineral fertilizer, 0.1x dried algae and wet algae, and 1x wet algae). Absolute and relative leaf area growth and estimated P uptake rates showed similar dynamics, indicating that wheat acquires P from algae quickly. A model proposes that algal fertilizer promotes wheat growth after rapid transformation in soil to inorganic nutrients. We conclude theoretically that phosphorus from algal biomass is available to wheat seedlings upon its application and is released gradually over time with minor differences related to moisture content on application. The growth and P uptake kinetics hint at nutrient forms, including N, and biomass stimulation worthy of research to further exploit algae in sustainable agriculture practices. Temporal resolved phenotype analyses in combination with a mass-balance approach is helpful for understanding resource uptake from recycled and biofertilizer sources by plants.
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ItemTime-resolution of the shoot and root growth of the model cereal Brachypodium in response to inoculation with Azospirillum bacteria at low phosphorus and temperature(Springer Verlag, 2021-01)A non-invasive plant phenotyping platform, GrowScreen-PaGe, was used to resolve the dynamics of shoot and root growth of the model cereal Brachypodium (Brachypodium distachyon Bd21-3) in response to the plant growth promoting (PGP) bacteria Azospirillum (Azospirillum brasilense Sp245). Inoculated Brachypodium plants had greater early vigor and higher P use efficiency than non-inoculated Brachypodium at low P and low temperature conditions. Root systems were imaged non-invasively at eight time points and data combined with leaf area, shoot biomass and nutrient content from destructive subsamples at 7, 14 and 21 days after inoculation (DAI). Azospirillum colonisation of roots improved Brachypodium shoot and, to a greater degree, root growth in three independent experiments. Inoculation promoted P use efficiency in shoots but not P concentration or uptake, despite increased total root length. Longer roots in inoculated plants arose from twofold faster branch root growth but slower axile root growth, detected at 11 DAI. Analysis of the spatio-temporal phenotypes indicated that the effects of Azospirillum inoculation increased as shoot P concentration declined, but the magnitude depended on the time after inoculation and growth rate of branch roots compared to axile roots. High throughput plant phenotyping platforms allow the details of plant-microorganism symbioses to be resolved, offering insights into the timing of changes in different tissues to allow molecular mechanisms to be determined.
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ItemAlleviation of salinity stress in plants by endophytic plant-fungal symbiosis: Current knowledge, perspectives and future directions(SPRINGER, 2020-07-09)Salinization of soil with sodium chloride ions inhibits plant functions, causing reduction of yield of crops. Salt tolerant microorganisms have been studied to enhance crop growth under salinity. This review describes the performance of endophytic fungi applied to crops as a supplement to plant genetics or soil management to alleviate salt stress in crops. This is achieved via inducing systemic resistance, increasing the levels of beneficial metabolites, activating antioxidant systems to scavenge ROS, and modulating plant growth phytohormones. Colonization by endophytic fungi improves nutrient uptake and maintains ionic homeostasis by modulating ion accumulation, thereby restricting the transport of Na+ to leaves and ensuring a low cytosolic Na+:K+ ratio in plants. Participating endophytic fungi enhance transcripts of genes encoding the high Affinity Potassium Transporter 1 (HKT1) and the inward-rectifying K+ channels KAT1 and KAT2, which play key roles in regulating Na+ and K+ homeostasis. Endophytic-induced interplay of strigolactones play regulatory roles in salt tolerance by interacting with phytohormones. Future research requires further attention on the biochemical, molecular and genetic mechanisms crucial for salt stress resistance requires further attention for future research. Furthermore, to design strategies for sustained plant health with endophytic fungi, a new wave of exploration of plant-endophyte responses to combinations of stresses is mandatory.