Root exudate ofSolanum tuberosumis enriched in galactose-containing molecules and impacts the growth ofPectobacterium atrosepticum

Abstract

Background and aims Potato (Solanum tuberosum) is an important food crop and is grown worldwide. It is, however, significantly sensitive to a number of soil-borne pathogens that affect roots and tubers, causing considerable economic losses. So far, most research on potato has been dedicated to tubers and hence little attention has been paid to root structure and function.Methods In the present study we characterized root border cells using histochemical staining, immunofluorescence labelling of cell wall polysaccharides epitopes and observation using laser confocal microscopy. The monosaccharide composition of the secreted exudates was determined by gas chromatography of trimethylsilyl methylglycoside derivatives. The effects of root exudates and secreted arabinogalactan proteins on bacterial growth were investigated using in vitro bioassays.Key Results Root exudate from S. tuberosum was highly enriched in galactose-containing molecules including arabinogalactan proteins as major components. Treatment of the root with an elicitor derived from Pectobacterium atrosepticum, a soil-borne pathogen of potato, altered the composition of the exudates and arabinogalactan proteins. We found that the growth of the bacterium in vitro was differentially affected by exudates from elicited and nonelicited roots (i.e. inhibition versus stimulation).Conclusions Taken together, these findings indicate that galactose-containing polymers of potato root exudates play a central role in root-microbe interactions.

The gut microbiome and metabolome of saddleback tamarins (Leontocebus weddelli): Insights into the foraging ecology of a small‐bodied primate

“…The presence of galactose, galactose‐derived metabolites (galactonic acid, galactopyranosides, galactonic acid), and arabinose in the tamarin metabolome also may indicate catabolism of arabinogalactans, a major component of plant exudates, including those of root origin (Bovo et al, ; Koroney et al, ). Along these lines, it is likely that the observed prevalence and functional relevance of soil‐dwelling and plant commensals is also connected with reliance on plant exudates.…”

Root extracellular traps versus neutrophil extracellular traps in host defence, a case of functional convergence?

“…Interestingly, pisatin was also found to stimulate production of pea border cells (Curlango‐Rivera et al , ) and therefore a pisatin–border cell feedback loop could operate during infection to maximize root protection. Similarly, an increase in arabinogalactan protein (AGP) production (and AGP release within the RETs themselves) was also shown to occur following pathogen infection or elicitor treatment (Cannesan et al , ; Koroney et al , ). These glycoproteins were found to inhibit growth of the pathogen Aphanomyces euteiches (Cannesan et al , ).…”

“…The root cap is a tissue located at the tip of growing plant root and consists of a combination of different cell types that provide protection to the meristematic stem cells during growth (Esau, ; Kumpf & Nowack, ). The root cap releases two categories of cell populations, known as border cells or border‐like cells, into the extracellular environment along with sugar‐containing ‘sticky’ secretions (known as root mucilage) (Hawes et al , , , ; Vicré et al , ; Driouich, Durand & Vicré‐Gibouin, ; Koroney et al , ). Border cells were characterized as individual cells detached from each other and border‐like cells as organized layers of several cells attached to each other (Hawes et al , ; Vicré et al , ; Driouich et al , ).…”

The role of rhizodeposits in shaping rhizomicrobiome

“…Senescent tissues and epidermic cells are quickly degraded to serve as important carbon sources, while border cells can remain alive for weeks or even months depending on the plant genotype (Hawes et al ., ; Hirsch et al ., ). After being released into the rhizosphere, border cells produce secondary metabolites such as antimicrobial substances, which contribute to the defence against phytopathogens (Cannesan et al ., ; Kang et al ., ; Koroney et al ., ). Soluble lysates originate from senescent rhizodermal and cortical cells, and account for a significant portion of the rhizodeposits (Nguyen, ).…”

“…Mucilage, synthesized by root cap cells and composed of polysaccharides and proteins, accounts for 2%–12% of the total rhizodeposits. Production of mucilage increases when plants are attacked by pathogens (Koroney et al ., ). Mucilage generally functions as a lubricant, chelator, humectant, aggregator, as well as a carbon source (Nguyen, ; Hirsch et al ., ).…”