GENETIC-ANALYSIS OF 2 TOMATO MUTANTS AFFECTED IN THE REGULATION OF IRON-METABOLISM

Iron is one of the most important micronutrients for plants. Like othe r organisms, plants have developed active mechanisms for the acquisiti on of sufficient iron from the soil. Nevertheless, very little is know n about the genetic mechanisms that control the active uptake. In toma to, two spontaneously derived mutants are available, which are defecti ve in key steps that control this process. The recessive mutation chlo ronerva (chin) affects a gene which controls the synthesis of the non- protein amino acid nicotianamine (NA), a key component in the iron phy siology of plants. The root system of the recessive mutant fer is unab le to induce any of the characteristic responses to iron deficiency an d iron uptake is thus completely blocked. We present a characterizatio n of the double mutant, showing that the fer gene is epistatic over th e chln gene and thus very likely to be one of the major genetic elemen ts controlling iron physiology in tomato. Icn order to gain access to these two genes at the molecular level, both mutants were precisely ma pped onto the high density RFLP map of tomato. The chin gene is locate d on chromosome 1 and the fer gene is on chromosome 6 of tomato. Using this high-resolution map, a chromosome walk has been started to isola te the fer gene by map-based cloning. The isolation of the fer gene wi ll provide new insights into the molecular mechanisms of iron uptake c ontrol in plants.