Intraspecies variation in cotton border cell production: rhizosphere microbiome implications.
OBJECTIVE
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. •


RESULTS
Emerging roots of some cultivars produced more than 20000 border cells per root, a 100% increase over previously 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.
Department of Soil, Water and Environmental Sciences, 429 Shantz Building #38, The University of Arizona, Tucson, Arizona 85721, USA.
Gilberto
G
Curlango-Rivera
David A
DA
Huskey
Ayman
A
Mostafa
John O
JO
Kessler
Zhongguo
Z
Xiong
Martha C
MC
Hawes
D001412:Bacillus subtilis / Q000502:physiology*; D003368:Gossypium / Q000166:cytology / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D054884:Host-Pathogen Interactions; D018519:Meristem / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D016973:Pectobacterium carotovorum / Q000502:physiology*; D010641:Phenotype; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D058441:Rhizosphere; D013045:Species Specificity
extracellular trap; rhizosphere; root border cells; root cap