Reduction of ferric iron by tumorous crown gall tissue is associated with cells modified by agro‐bacterium tumefaciens

Abstract

Iron (Fe) uptake and use in plants is genetically controlled and physiological mechanisms such as Fe reduction are induced during Fe‐deficiency stress to make it available. Transfer of DNA into the cell genome by Agrobacterium tumefaciens alters physiological processes and causes undifferentiated growth. Tumor cells in sunflower (Helianthus annus L. cv. Mammoth Russian) show enhanced Fe reduction compared to normal stem tissue in a manner similar to root cells in plants that are genetically switched on or off to manage Fe acquisition. This study addresses whether alterations caused by the DNA transfer from A. tumefaciens result in Fe reduction or whether A. tumefaciens inoculum alone reduces Fe. Reduction of Fe was quantified from A. tumefaciens inoculum and from uninoculated or inoculated sunflower stem tissues daily over a 14‐day period. Neither A. tumefaciens inoculum nor uninoculated stem tissue alone activated massive Fe reduction. High rates of Fe reduction were associated with the proliferation of cells modified by A. tumefaciens. The mechanisms that transformed normal tissue to uncontrolled tumor growth appeared to be linked to active Fe reduction. These modified cells may provide a key to locating and understanding the genetic control of the Fe reduction process in plant cells. Our results suggest a critical role for Fe in development of tumorous tissues and raises the question of whether other tumor cells induce similar mechanisms for Fe acquisition.