Cloning And Expression Analysis Of TpNRAMPs From Dwarf Polish Wheat (Triticum Polonicum)

NRAMP (Natural resistance-associated macrophage proteins) consist of a group of highly conserved integral membrane proteins and exist widely in bacteria, fungi, plant and animal. The first NRAMP, Nrampl which controls mouse natural resistance of parasite, was identified in mouse. NRANP participate in plant heavy metal transport and resistance against the bacterial pathogen. Up to date, six AtNRAMPs and seven OsNRAMPs were identified from Arabidopsis and rice, respectively. However, NRAMP homology genes in wheat are rarely reported.Polish wheat (2n=4x=28, AABB, Triticum polonicum) may be a hydrization between T. ispahanicum and T. durum. Its genetic similarity is very low with bread wheat and other tetraploid wheat. Dwarf polish wheat (DPW) is a spontaneous mutant dwarf accession of T. polonicum, originally collected from Tulufan, Xinjiang, China. It is characterized as dwarfism and long panicle. Our previous studies indicated that DPW also accumulated high concentrations of Cd and Zn in roots and leaves. However, its molecular mechanism is unknown. NRAMP play important role in plant metal tolerance. The object of this study was to identify NRAMP homology genes in DPW and investigated the expression pattern of TpNRAMPs under heavy metal treatments. The results were listed below:1. DPW exhibited a relatively strong capability in metal tolerance. After 24 hours heavy metal treatments, leaves and roots accumulated a high metal concentration. The concentrations of copper were 125.88 mg/g and 38.53 mg/g in roots and leaves, respectively. Meanwhile, the growth of plants were significantly reduced. The accumulations of Cd, Zn and Fe in leaves and roots were high without remarkable effect on growth, provided evidence of DPW's ability in metal tolerance.2. In the present study, five NRAMP homology genes, named as TpNramp2.1, TpNRAMP2.2, TpNRAMP3, TpNRAMP5 and TpNRAMP6, were cloned and characterized in DPW. Further, we got TaNrampl, TaNramp7 and an unnamed TaNRAMP blasting against the draft wheat genome. There are thereforce at least seven NRAMP homology genes in wheat.3. The expression patterns of TpNRAMP2.1, TpNRAMP3, TpNRAMP5 and TpNRAMP6 under seven metal treatments were difference. TpNRAMP2.1 was most sensitive to Mg, Fe and Cu in roots, and was most sensitive to Mg and Zn in leaves. TpNRAMP3 was significant up-regulation under Fe, Cu and Cd treatment in roots, and was most sensitive to Cu in leaves. TpNRAMP5 was most sensitive to Fe and Zn in roots, and was most sensitive to Cd in leaves. Lastly, TpNRAMP6 was most sensitive to Fe in roots and was sensitive to Mg and Zn in leaves. Also, these genes were all most sensitive to Fe in root of DPW.