DNA Is Taken Up by Root Hairs and Pollen, and Stimulates Root and Pollen Tube Growth

Phosphorus (P) enters roots as inorganic phosphate (P-i) derived from organic and inorganic P compounds in the soil. Nucleic acids can support plant growth as the sole source of P in axenic culture but are thought to be converted into P-i by plant-derived nucleases and phosphatases prior to uptake. Here, we show that a nuclease-resistant analog of DNA is taken up by plant cells. Fluorescently labeled S-DNA of 25 bp, which is protected against enzymatic breakdown by its phosphorothioate backbone, was taken up and detected in root cells including root hairs and pollen tubes. These results indicate that current views of plant P acquisition may have to be revised to include uptake of DNA into cells. We further show that addition of DNA to P-i-containing growth medium enhanced the growth of lateral roots and root hairs even though plants were P replete and had similar biomass as plants supplied with P-i only. Exogenously supplied DNA increased length growth of pollen tubes, which were studied because they have similar elongated and polarized growth as root hairs. Our results indicate that DNA is not only taken up and used as a P source by plants, but ironically and independent of Pi supply, DNA also induces morphological changes in roots similar to those observed with P limitation. This study provides, to our knowledge, first evidence that exogenous DNA could act nonspecifically as signaling molecules for root development.