Kamlesh K. Meena

Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants: The Omics Strategies

Abiotic stresses are the foremost limiting factors for agricultural productivity. Crop plants need to cope up adverse external pressure created by environmental and edaphic conditions with their intrinsic biological mechanisms, failing which their growth, development, and productivity suffer. Microorganisms, the most natural inhabitants of diverse environments exhibit enormous metabolic capabilities to mitigate abiotic stresses. Since microbial interactions with plants are an integral part of the living ecosystem, they are believed to be the natural partners that modulate local and systemic mechanisms in plants to offer defense under adverse external conditions. Plant-microbe interactions comprise complex mechanisms within the plant cellular system. Biochemical, molecular and physiological studies are paving the way in understanding the complex but integrated cellular processes. Under the continuous pressure of increasing climatic alterations, it now becomes more imperative to define and interpret plant-microbe relationships in terms of protection against abiotic stresses. At the same time, it also becomes essential to generate deeper insights into the stress-mitigating mechanisms in crop plants for their translation in higher productivity. Multi-omics approaches comprising genomics, transcriptomics, proteomics, metabolomics and phenomics integrate studies on the interaction of plants with microbes and their external environment and generate multi-layered information that can answer what is happening in real-time within the cells. Integration, analysis and decipherization of the big-data can lead to a massive outcome that has significant chance for implementation in the fields. This review summarizes abiotic stresses responses in plants in-terms of biochemical and molecular mechanisms followed by the microbe-mediated stress mitigation phenomenon. We describe the role of multi-omics approaches in generating multi-pronged information to provide a better understanding of plant–microbe interactions that modulate cellular mechanisms in plants under extreme external conditions and help to optimize abiotic stresses. Vigilant amalgamation of these high-throughput approaches supports a higher level of knowledge generation about root-level mechanisms involved in the alleviation of abiotic stresses in organisms.

Rhizosphere Signaling Cascades: Fundamentals and Determinants

Molecular interactions among the plants and microbes represent an important microecological phenomenon. The cross talk involves multiple ecological aspects like exchange of metabolites, signaling and chemotaxis, etc. These bilateral interactions are crucial for the health and development of both the plant and colonizing microbes. The signal molecules play major role as inducers of different pathways that contribute indispensable role for the survival of the participants under adverse circumstances and development of symbiotic associations as well. Though the recent high-throughput techniques have generated considerable data regarding the molecular exchanges happening in the rhizosphere microbes and the host, our current knowledge in this area is still in infancy. It is thus critical to get deeper insights of such interactions so as to develop next-generation strategies relating to the sustainable agriculture under the changing climate scenario. We describe herewith the major aspects concerning the contributors and their role in rhizosphere signaling cascades and the consequent post-signaling responses given by the host and the colonizing microbes.

Role of Microorganisms in Alleviating Abiotic Stresses

Constantly changing agroclimatic scenario has raised serious threats to agricultural production and productivity nowadays. Current attempts toward attenuation of abiotic stressor(s) have met limited success. Among the several strategies proposed, microbial mitigation of abiotic stresses has gained rapid attention, particularly in light of its sustainable and green approach that utilizes the natural phenomenon of plant-microbe association and subsequent beneficial interactions. The role of phyllosphere, rhizosphere, and endophytic microorganisms in mitigating a variety of abiotic stressors is well known. However, limited information is available till date regarding the cumulative influence of abiotic stressor(s) on plant-microbe association and on the stress-mitigation potential of microorganisms as well. Microbial inoculation is frequently recommended under stress-prone environment; however, it appears quite crucial to understand the behavior of inoculants under stressed habitats, which could substantially reduce the failure encountered by microbial inocula. This chapter typically highlights the plant-microbial interactions under abiotic stresses, microbial adaptations, and the role of stress-resilient microbes in alleviating the same.