The Microbially Extended Phenotype of Plants, a Keystone against Abiotic Stress

Abstract

Background: Climate change affects every region across the globe with heterogeneous effects on local temperatures and precipitation patterns. In plants, sessile organisms, climate change imposes more drastic effects leading to loss of yield or even death. However, plants establish mutualistic interactions with microorganisms that boost plant tolerance against abiotic stresses or strengthen the plant immune system against pathogens, thus, enhancing their survival and fitness. Moreover, in the wild, microbial endophytes provide important ecosystem services. Purpose and scope: Little we know about the mechanisms of response against the adverse effects of climate change on natural populations of wild plants and even less about the potential role played by microbial biostimulants. In this article, we review the effects of biostimulants on plant responses against abiotic stresses, with a particular focus on the role of mycorrhizas and leaf endophytes. Results: We have reviewed the effects of the main abiotic stresses in plants, the mechanisms that plants use to face these abiotic challenges, and the interaction plant-biostimulant-abiotic stress, highlighting the primary responses and parameters to evaluate different plant responses. Conclusion: Abiotic stresses can check the phenotypic plasticity of plants and also trigger a complex and heterogeneous array of responses to face different abiotic stresses, and beneficial microorganisms do play an essential role in enhancing such responses. Our laboratory has initiated a project to characterise microbial populations associated with plants from wild areas and analyse their potential role in aiding the plants to cope with abiotic stresses.

Plants as the Extended Phenotype of Endophytes—The Actual Source of Bioactive Compounds

“…Apart from this, as suggested by Hunter and revised by others, the plant–soil interaction is the primary example of a novel understanding of an extended phenotype, as plants and their associated microbiota can affect the soil composition by expressing their genes, thereby favoring the growth of one type of microbial or plant species over another [ 6 , 9 , 10 , 11 ]. Alternately, the plant itself can be considered to be the extended phenotype of the microorganisms inhabiting its tissues, whether as pathogens or non-causing apparent diseases, because they contribute to the overall phenotype of the plant by producing bioactive compounds themselves [ 12 , 13 , 14 ].…”