The Mechanism Of BTS Gene In Plant Response To Excessive Zinc Stress

Large amounts of zinc has been inputted into soils due to urbanization,transportation,mining,sewage sludge application,sewage irrigation,as well as the application of organic fertilizers containing zinc.As a result,zinc concentration in man agricultural soils exceeds the permitted levels.Phytoremediation is an important strategy for restoring zinc-contaminated soils.Identification of key genes regulating zinc accumulation and tolerance in plants is an important theoretical basis for improving the phytoremediation efficiency of target plants.The accumulation of zinc in plants is related to other elements,especially iron.E3 ligase BRUTUS plays an important role in regulating iron uptake and homeostasis in plants,but whether this regulatory element also plays a role in zinc accumulation and tolerance in plants is unclear.In this study,we used the E3 ligase BRUTUS related mutant of Arabidopsis thaliana as the material,to study the roles and mechanisms of BTS gene in plant response to zinc exposure by physiological and molecular biological methods.The main results are summarized as follows:The effects of zinc stress on the growth and zinc accumulation of Arabidopsis wild-type Col-0 and BTS knockdown bts-1 mutants were studied on agar medium.Results showed that zinc tolerance of bts-1 was better than Col-0,and the shoot phenotypic difference between these two genotypes was particularly significant.Nevertheless,the zinc level of root in bts-1 mutants was higher than that in Col-0,although there was no significant difference in the shoot between the two genotypes.The gene expression analysis showed that zinc exposure induced the expression of BTS in roots.The fluorescence intensity of BTS protein under zinc exposure was further observed in p BTS::BTS-GFP transgenic plants,which indicated that the zinc exposure also induced the accumulation of BTS protein in root tissues.These results suggested that BTS negatively regulates plant tolerance to zinc stress.abstractIn order to elucidate the mechanism underlying the differences in zinc tolerance between Col-0 and bts-1,we compared the differences in gene expression between the two genotypes.The results showed that the transcriptional changes of Col-0 and bts-1mutants were significantly different under zinc stress,namely that the bts-1 mutants significantly up-regulated the expression of genes involved in iron absorption,transport and regulation such as FIT,b HLH038,b HLH039,b HLH100,IRT1,FRO2,FRD3 and MYB10,compared with Col-0 plants.This result suggests that BTS gene knockdown may enhance zinc tolerance by inducing the expression of iron nutrition-related genes.Further analysis showed that the iron level was no significant difference in both roots and shoots between two genotypes under normal growth conditions,but the iron level of bts-1 mutants under zinc exposure was significantly higher than that of Col-0.Furthermore,a series of iron dose were supplied to Col-0 and bts-1 plants,and we found that with the increase of iron supplementation,the plants were less susceptible to zinc toxicity,together with the phenotypic differences between these two genotypes being decreased.In addition,under zinc exposure,iron absorption-related mutant fro2 and iron transport-related mutant frd3 had more zinc toxicity than Col-0,but growth of the latter mutant could be restored by exogenous citric acid supplement.In conclusion,BTS gene knockdown enhances plant tolerance to zinc stress by improving plant iron nutrition via inducing the expression of iron nutrition-related genes.