Roots: Contribution to the Rhizosphere

Abstract

Diverse compounds exuded by different parts of the root system create a unique environment known as the rhizosphere. Interactions among microorganisms found within the rhizosphere and communication between these microorganisms and plant roots play an important role in maintaining plant health. In 2004, the discovery of deoxyribonucleic acid (DNA)‐based neutrophil extracellular traps (NETs) have transformed our understanding of mammalian immune responses. Subsequent studies revealed that plant roots express a similar mechanism in the rhizosphere, where root border cells secrete extracellular DNA together with antibiotic amino acids, enzymes and other proteins, to trap pathogens and prevent their invasion of the root system. As in animals, the defense response is impaired if extracellular proteins and/or extracellular DNA are degraded by protease and/or by DNase at the time of inoculation with fungal or bacterial pathogens. Defining species‐specific mechanisms of plant extracellular trapping may yield new avenues for engineering the rhizosphere to improve crop production. Key Concepts Extracellular DNA (exDNA) in the rhizosphere has long been observed, and was presumed to result from cell death. Recent studies have revealed that exDNA is a key component of an extracellular matrix involved in trapping and immobilisation of pathogens. The specificity of exDNA‐based trapping may play a critical role in microbial population structure in the rhizosphere. The discovery that DNA‐based extracellular trapping operates in animals and plants suggests that this previously unrecognised process is an ancient underpinning of eukaryotic defence. Efforts to engineer the rhizosphere may be facilitated by a better understanding of how plants control the environment surrounding their roots.

Changes in the Distribution of Pectin in Root Border Cells Under Aluminum Stress

“…RBCs and mucilages have been shown to protect root tips from chemical and biological stresses, such as iron toxicity (Xing et al, 2008) and fungal infection (Hawes et al, 2000; Gunawardena and Hawes, 2002). Previous reports showed that the presence of RBCs and mucilages decreases Al accumulation and increases Al tolerance (Barcelo and Poschenrieder, 2002; Curlango-Rivera et al, 2016; Hawes et al, 2016). Al-resistant plants tend to have less Al accumulation than do Al-sensitive plants (Ma et al, 2005).…”

Sequencing of the Whole Genome of a Bacterium of the Genus Achromobacter Reveals Its Potential for Xenobiotics Biodegradation

“…77Bb1, some genes for plant growth hormones (brassinosteroid, flavone, flavonol, flavonoid, isoflavonoid, isoquinoline, phenylpropanoid, stilbenoid, diarylheptanoid, gingerol, tropane, piperidine, pyridine alkaloid, and zeatin) and antibiotics (novobiocin, penicillin, cephalosporin, puromycin, streptomycin, and tetracycline) were found. This indicates the ability of this bacterium to influence plant growth and development by increasing its ability to survive in a given environment [56,58]. Genes encoding aldehyde dehydrogenase, nitrilotriacetate monooxygenase (components A and B), 3-hydroxyacyl-CoA dehydrogenase, enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, acyl-CoA synthetase, flavodoxin reductases, and probable poly(beta-D-mannuronate) O-acetylase, present in genome of Achromobacter sp.…”