The Endophytic Microbiome as a Hotspot of Synergistic Interactions, with Prospects of Plant Growth Promotion

Abstract

The plant root is the primary site of interaction between plants and associated microorganisms and constitutes the main components of plant microbiomes that impact crop production. The endophytic bacteria in the root zone have an important role in plant growth promotion. Diverse microbial communities inhabit plant root tissues, and they directly or indirectly promote plant growth by inhibiting the growth of plant pathogens, producing various secondary metabolites. Mechanisms of plant growth promotion and response of root endophytic microorganisms for their survival and colonization in the host plants are the result of complex plant-microbe interactions. Endophytic microorganisms also assist the host to sustain different biotic and abiotic stresses. Better insights are emerging for the endophyte, such as host plant interactions due to advancements in ‘omic’ technologies, which facilitate the exploration of genes that are responsible for plant tissue colonization. Consequently, this is informative to envisage putative functions and metabolic processes crucial for endophytic adaptations. Detection of cell signaling molecules between host plants and identification of compounds synthesized by root endophytes are effective means for their utilization in the agriculture sector as biofertilizers. In addition, it is interesting that the endophytic microorganism colonization impacts the relative abundance of indigenous microbial communities and suppresses the deleterious microorganisms in plant tissues. Natural products released by endophytes act as biocontrol agents and inhibit pathogen growth. The symbiosis of endophytic bacteria and arbuscular mycorrhizal fungi (AMF) affects plant symbiotic signaling pathways and root colonization patterns and phytohormone synthesis. In this review, the potential of the root endophytic community, colonization, and role in the improvement of plant growth has been explained in the light of intricate plant-microbe interactions.

Probiotic Endophytes for More Sustainable Banana Production

“…More recently, microbiologists have been using high-throughput sequencing (HTS) methods to explore the structure of bacterial communities, identifying members that cannot be easily cultured in the laboratory [ 35 , 36 , 37 ], including phyla such as Planctomycetes, Verrucomicrobia, and Acidobacteria [ 38 , 39 ]. A significant proportion of the bacterial genera reported as endophytic is commonly found in the rhizosphere, suggesting that the endophytic microbiome may be a subpopulation of the rhizospheric bacteria [ 14 ].…”

“…Endophytic bacteria reside in the internal tissues of the plant, establishing a strong symbiotic relationship that promotes plant growth and provides protection in exchange for a niche to carry out its life cycle [ 14 ]. The nature of their mutualistic association depends on their location in the plant tissue, either intercellularly or intracellularly [ 15 , 16 ].…”

Multi-Trait Wheat Rhizobacteria from Calcareous Soil with Biocontrol Activity Promote Plant Growth and Mitigate Salinity Stress

“…Indole acetic acid production of PGPR strains is one of their major properties, considered as one of the most physiologically active phytohormones that improves plant growth, supports plant cell division, influences the multiplication of root hairs, controls the differentiation of root meristem and affects the root system by increasing length and weight in main roots and lateral root number. These benefits enhance nutrients acquisition and improve plants’ development and yield [ 68 , 71 , 72 , 73 ]. The IAA producing quantity of the arylsulphatase-producing strains (ranged from 2.35 ± 0.6 to 28.35 ± 0.8 μM mL −1 ) seem to be effective for plant growth promotion of plants.…”

Phenotype Switching in Metal-Tolerant Bacteria Isolated from a Hyperaccumulator Plant

“…It is known that microorganisms associated with plants (the so-called plant microbiome) are able to produce many compounds, e.g., phytohormones (auxins or cytokinins), antibiotics, and enzymes (hydrolases and proteases attacking pathogens cells), which ensure plant protection against pathogens and improve plant growth and development. Such microbes are termed Plant Growth-Promoting Bacteria (PGPB) [ 1 , 2 ]. This ability is also observed during plant exposure to contaminants and other stress factors (e.g., temperature, drought, pH); it may help plants to cope with adverse factors or even increase their potential to remove the contaminants.…”

“…Based on the preliminary work [ 9 ], we hypothesized that the microorganisms would be able to synthesize the Indole-3-Acetic Acid (IAA) phytohormone and hydrolytic enzymes, namely cellulases, xylanases, and proteases at exposure to selected doses of metals studied previously. The synthesis of hydrolytic enzymes is extremely important from the point of view of colonization of plant tissues by the studied endophytes [ 2 ].…”