Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants: The Omics Strategies
The symbiosis between some plant species and nitrogen-fixing nodule bacteria is one of the most relevant cooperative relationships in the world. It shapes our. This chapter deals with the cold tolerance/resistance mechanisms operating in cold adaptation is the activity–stability–ﬂexibility relationship, which suggests that .. Azospirillum is an associative symbiotic plant growth promoting bacterium . Sep 3, Beyond fungi, some plants engage in symbiosis with bacteria called rhizobia that “fix” nitrogen from the atmosphere, making it available to the.
The area under ever-increasing salinization has almost reached 34 million irrigated hectares FAO, 2. Although any accurate estimation of agricultural loss reduction of crop production and soil health in terms of agro-ecological disturbances due to abiotic stresses could not be made, it is evident that such stresses affect large land areas and significantly impact qualitative and quantitative loss in crop production Cramer et al.
Plants frequently cope up with the rapid fluctuations and adversity of environmental conditions because of their intrinsic metabolic capabilities Simontacchi et al.
Variations in the outside environment could put the plant metabolism out of homeostasis Foyer and Noctor,and create necessity for the plant to harbor some advanced genetic and metabolic mechanisms within its cellular system Apel and Hirt, ; Gill and Tuteja, Plants possess an array of protective mechanisms acquired during the course of evolution to combat adverse environmental situations Yolcu et al.
Such mechanisms cause metabolic re-programming in the cells Heil and Bostock, ; Swarbrick et al. Many times plants get facilitated in reducing the burden of environmental stresses with the support of the microbiome they inhabit Turner et al. Microbial life is the most fundamental and live system on the earth. Being important living component of the soils, they naturally become integral part of the crop production system as soon as a seed comes into the soil to start its life cycle.
Plant–Microbe Communications for Symbiosis | Plant and Cell Physiology | Oxford Academic
Microorganisms are important inhabitants of seeds also, and proliferate as the seeds grow in the soils to form symbiotic associations at the surface or endophytic interactions inside the roots, stems or leaves. Plant microbiome provides fundamental support to the plants in acquiring nutrients, resisting against diseases and tolerating abiotic stresses Turner et al.
Microbial intrinsic metabolic and genetic capabilities make them suitable organisms to combat extreme conditions of the environment Sessitsch et al. Their interactions with the plants evoke various kinds of local and systemic responses that improve metabolic capability of the plants to fight against abiotic stresses Nguyen et al. A testament to the important attributes of the microbial interactions with plants is significant number of accumulating pieces of evidence that suggest in-depth mechanisms based on plant—microbe interactions that offer modulation of cellular, biochemical and molecular mechanisms connected with stress tolerance Bakker et al.
The advent of next-generation sequencing NGS facilities supported gradually increasing metagenomic work and consequently led to the accumulation of greater amount of data for functional characterization of microbial communities in the soils Bulgarelli et al. Work on plant—microbe interactions at biochemical, physiological and molecular levels established that microbial associations largely direct plant responses toward stresses Farrar et al. For dissecting deeper interaction mechanisms and connecting the changes at molecular levels with the tolerance responses against stresses, biological data based on the multi-omics approaches were generated Kissoudis et al.
Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants: The Omics Strategies
Technological developments also facilitated understanding of gene editing systems, RNAi-mediated gene silencing, mutant technology, proteomic analysis and metabolite profiling to reveal voluminous molecular information that helped in improving our understanding of microbe-mediated mitigation strategies of abiotic stresses in plants Yin et al.
Multi-omics approaches have emerged as a holistic and integrated analytical strategies for the dissection of one of the most complex and dynamic living system of microbial interactions with plants and modulating the consequences developed in the plants to help them overcome stresses. The fatty acids were grouped in 3 main clusters and 5 sub-clusters. Heatmap visualization of fatty acids from total lipids present in Mesorhizobium N33 during growth at different temperatures.
The fatty acids were grouped in 3 main clusters and 8 sub-clusters in Heatmaps. The heatmap visualization shows different trends of metabolite changes under each time exposure at low temperature. Confirmations by spiking with standard and original peaks of unexpected metabolites. The key molecular mechanisms underlying cold adaptation in Arctic rhizobia remains totally unknown. Since the concentration and contents of metabolites are closely related to stress adaptation, we applied GC-MS and NMR to identify and quantify fatty acids and water soluble compounds possibly related to low temperature acclimation in strain N As reported in the literature, these fatty acids play important roles in cold adaptability by supplying cell membrane fluidity, and by providing energy to cells.
Isobutyrate was highly upregulated Introduction Bacteria have developed many strategies at the transcriptional and post-transcriptional levels to enhance their abilities to withstand cold temperature stress. Some molecular responses to stress are general while others can be specific . The specific cold adaptive features in bacteria include global resource efficiency, amino acid substitution in cold-active enzymes and increased substrate transport systems .
Low temperatures also regulate transcripts encoding for specific enzymes e. A genome sequence analysis study of the psychrophilic Antarctic bacterium Pseudoalteromonas haloplanktis TAC, suggested that elimination of the entire metabolic pathways involved in ROS generation, can protect the cell against the accumulation of deleterious dioxygen scavenging .
Like in many other cold-loving bacteria, the synthesis of lipid desaturases has also been detected in strain TAC These enzymes increase membrane fluidity, and protect the cell against dioxygen and detoxify the cells at low temperature. On the other hand, as a general response, housekeeping genes are also regulated by a variety of stressors including low temperature which allows these bacteria to down-regulate their metabolism to optimize general cell functions in order to withstand cold stresses.
Other general response mechanisms include higher turnover of macromolecules, tighter maintenance of intercellular pH, greater osmotic regulation, motility, stopping biomass production and decreasing the activation energy before a pre-exponential growth phase .Symbiosis
Reduction of growth and suppression of the genes involved in translation and ribosomal biogenesis in E. Transcriptional analysis of the Arctic Mesorhizobium N33 revealed the down-regulation of many housekeeping genes that encode for the cell envelope and outer membrane biogenesis functions, as well as cell motility and secretion at low temperature unpublished data.
Among these phenomena, nodule senescence, namely regulation of nodule lifespan, is uncharted territory but would gain in importance when our aim is to achieve long-term nitrogen-fixing activity in legumes. The MtATB2 gene encodes a bZIP transcription factor and is regulated by sucrose and light conditions as well as during nodule senescence.
For nodule function, carbon is provided mainly as sucrose derived from photosynthesis and transported via the phloem. Leguminous plants strictly control nodule numbers, because nodulation and nitrogen fixation are an energy drain on the host. To maintain the symbiotic balance with rhizobia, plants have evolved negative feedback systems known as autoregulation of nodulation AON.
Thus, plenty is invaluable for dissecting the complex web of negative regulatory systems in nodulation. The homologs are widely conserved in non-leguminous plants but their functions are unknown.
Transformation with OsNSP1 and OsNSP2 fully rescued the mutant phenotypes such as nodule development and nitrogenase activity, indicating that these rice transcription factors can potentially mediate Nod factor signaling in L.
Bacterial factors in RN symbiosis In response to stimulation by flavonoids exuded from legume roots into soil, rhizobia synthesize signaling molecules that are responsible for nodule formation. These signaling molecules, named Nod factors, have been identified as lipochito- oligosaccharides decorated with diverse chemical substitutions Spaink In this special issue, Maruya and Saeki examine the physiological functions of the BacA homolog in Mesorhizobium loti.
From study of a bacA mutant, they found that BacA is dispensable for M.