Zinc up-regulated the expression of the rice metallonthionein gene family and enhanced the zinc tolerance of yeast cells

摘要

Northern blot and functional complementation assay were employed to analyze the effects of zinc on expression of ten rice metallothionein genes (OsMT-Is) in rice seedlings and the growth of yeast cells transformed with OsMT-Is. Northern blot revealed that in shoots of the rice seedlings treated with different Zn~(2+) concentrations, expression of most members of OsMT-I family was increased, except the type 4 OsMT-Is (OsMT-I-4a, 4b and 4c). In roots, Zn~(2+) significantly increased the transcription of OsMT-I-1b and OsMT-I-2c, but reduced the trascription of OsMT-I-1a and OsMT-I-3a . When these ten cDNAs were heterologously expressed in zinc sensitive yeast mutant, all transgenic yeasts showed increased tolerance to Zn~(2+) , and zinc accumulation in these yeast cells also increased. These indicated that OsMT-I family members might respond to extra Zn~(2+) , and they could enhance Zn~(2+) tolerance of cells by direct binding Zn~(2+).