Linking Plant Nutritional Status to Plant-Microbe Interactions

Abstract

Plants have developed a wide-range of adaptations to overcome nutrient limitation, including changes to the quantity and composition of carbon-containing compounds released by roots. Root-associated bacteria are largely influenced by these compounds which can be perceived as signals or substrates. Here, we evaluate the effect of root exudates collected from maize plants grown under nitrogen (N), phosphate (P), iron (Fe) and potassium (K) deficiencies on the transcriptome of the plant growth promoting rhizobacterium (PGPR) Bacillus amyloliquefaciens FZB42. The largest shifts in gene expression patterns were observed in cells exposed to exudates from N-, followed by P-deficient plants. Exudates from N-deprived maize triggered a general stress response in FZB42 in the exponential growth phase, which was evidenced by the suppression of numerous genes involved in protein synthesis. Exudates from P-deficient plants induced bacterial genes involved in chemotaxis and motility whilst exudates released by Fe and K deficient plants did not cause dramatic changes in the bacterial transcriptome during exponential growth phase. Global transcriptional changes in bacteria elicited by nutrient deficient maize exudates were significantly correlated with concentrations of the amino acids aspartate, valine and glutamate in root exudates suggesting that transcriptional profiling of FZB42 associated with metabolomics of N, P, Fe and K-deficient maize root exudates is a powerful approach to better understand plant-microbe interactions under conditions of nutritional stress.

Isolation, Characterization and Selection of Bacteria that Promote Plant Growth in Grapevines (Vitis sp.)

“…Direct growth-promoting mechanisms are those that affect the plant's natural balance of growth regulators, improving its nutritional proficiencies and stimulating the processes that fight systemic diseases (for example, biological nitrogen fixation, phytohormones production, synthetization of enzymes, inorganic phosphate solubilization, and phosphate mineralization). Indirect growth regulator mechanisms, on the other hand, are the ones that reduce or inhibit the activities of pathogenic microorganisms through biocontrol, which includes the production of antibiotics and iron chelating agents (siderophores), and the synthetization of exoenzymes, such as cellulases and chitinases (Carvalhais et al, 2013;F. Ahmad, I. Ahmad, & Khan, 2008;Zahir, Asghar, Akhtar, & Arshad, 2005;Asghar, Zahir, Arshad, & Khaliq, 2002).…”

Effect of <i>Pseudomonas fluorescens</i> and <i>Burkholderia pyrrocinia</i> on the Growth Improvement and Physiological Responses in <i>Brachiaria brizantha</i>

“…On the other hand, inoculation with rhizobacteria increased growth in unfertilized plants (i.e., exposed to nutrient limitation) ( Table 1). It could be inferred that roots of unfertilized plants modified rhizodeposition patterns, by secreting specific compounds, resulting in an increased microbial biomass and activity around the roots [6] [28]. In maize plants, the nutritional status affects the root colonizing bacterium, stimulating the repression of genes associated with protein synthesis, changing the composition of root exudates, and influencing the physiology of associative bacteria [28].…”

“…It could be inferred that roots of unfertilized plants modified rhizodeposition patterns, by secreting specific compounds, resulting in an increased microbial biomass and activity around the roots [6] [28]. In maize plants, the nutritional status affects the root colonizing bacterium, stimulating the repression of genes associated with protein synthesis, changing the composition of root exudates, and influencing the physiology of associative bacteria [28]. In temperate grasslands, Keuter et al, (2014) observed that fertilization decreases non-symbiotic biological N fixation, through the inhibition of nitrogenase [14].…”

Effects of rhizobacteria on the respiration and growth of Cerasus sachalinensis Kom. seedlings

“…Seed germination experiments were conducted at a constant temperature of 20°C in an incubator (LHS-3-acetic acid (IAA; Zak et al, 2003), alters the nutritional status of the rhizosphere (Carvalhais et al, 2013) and can induce disease resistance (Annapurna et al, 2013). Various microbial species are present in the soil, but only few of them have certain advantages and significantly impact on plant growth (Kamal et al, 2015).…”