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PREMISE OF THE STUDY:: Root border cells are programmed to separate from the root cap as it penetrates the soil environment, where the cells actively secrete >100 extracellular proteins into the surrounding mucilage. The detached cells function in defense of the root tip by an extracellular trapping process that also requires DNA, as in mammalian white blood cells. Trapping in animals and plants is reversed by treatment with DNase, which results in increased infection. The goal of this study was to evaluate the role of DNA in the structural integrity of extracellular structures released as border cells disperse from the root tip upon contact with water. METHODS:: DNA stains including crystal violet, toluidine blue, Hoechst 33342, DAPI, and SYTOX green were added to root tips to visualize the extracellular mucilage as it absorbed water and border cell populations dispersed. DNase I was used to assess structural changes occurring when extracellular DNA was degraded. KEY RESULTS:: Complex masses associated with living border cells were immediately evident in response to each stain, including those that are specific for DNA. Treating with DNase I dramatically altered the appearance of the extracellular structures and their association with border cells. No extracellular DNA was found in association with border cells killed by freezing or high‐speed centrifugation. This observation is consistent with the hypothesis that, as with border cell extracellular proteins, DNA is secreted by living cells. CONCLUSION:: DNA is an integral component of border cell extracellular traps. [ABSTRACT FROM AUTHOR]

* Premise of the study: Border cells, which separate from the root cap, can comprise >90% of carbon-based exudates released into the rhizosphere, but may not provide a general source of nutrients for soil microorganisms. Instead, this population of specialized cells appears to function in defense of the root tip by an extracellular trapping process similar to that of mammalian white blood cells. Border cell production is tightly regulated, and direct tests of their impact on crop production have been hindered by lack of intraspecies variation. * Methods: Border cell number, viability, and clumping were compared among 22 cotton cultivars. Slime layer "extracellular trap" production by border cells in response to copper chloride, an elicitor of plant defenses, was compared in two cultivars with divergent border cell production. Trapping of bacteria by border cells in these lines also was measured. * Key results: Emerging roots of some cultivars produced more than 20000 border cells per root, a 100% increase over previ ously reported values for this species. No differences in border cell morphology, viability, or clumping were found. Copper chloride-induced extracellular trap formation by border cells from a cultivar that produced 27921 ±2111 cells per root was similar to that of cells from a cultivar with 10002 ±614 cells, but bacterial trapping was reduced. * Conclusions: Intraspecific variation in border cell production provides a tool to measure their impact on plant development in the laboratory, greenhouse, and field. Further research is needed to determine the basis for this variation, and its impact on rhizosphere community structure. [ABSTRACT FROM AUTHOR]