The Function Of PLATZ5,a Zinc-finger Transcription Factor Of Arabidopsis Thaliana,in Response To Salinity Stress

Soil salinization is one of the most important factors affecting crop yield and quality.The high concentration of salt in the soil can lead to the disturbance of plant metabolism,which will affect the absorption of the essential nutrient of plants,cause osmotic stress and oxidative stress,and then affect plant growth and development.How to improve the salt tolerance of plant has become an urgent problem in agricultural development.PLATZ(Plant A/T rich sequence-and zinc-binding protein)is a class of plant specific transcription factors.The first reported PLATZ1 from pea can non-specifically bind to the A/T rich sequence to play a role in transcription repression.There are 12 PLATZ members in Arabidopsis thaliana.In this study,AtPLATZ5 was studied,and its function in abiotic stresswas identified.The results were as following:(1)The expression pattern of AtPLATZ5 was detected by semi-quantitative RT-PCR and GUS staining.The results showed that AtPLATZ5 was expressed in various tissues,and the expression was not significantly different.The results of RT-PCR and qRT-PCR also showed that the expression of AtPLATZ5 was induced by salt stress.(2)The subcellular localization analysis of PLATZ5 showed that PLATZ5 localized not only in the nucleus but also in the cytoplasm,indicating that PLATZ5 may have multiple functions.(3)The transcriptional activity of PLATZ5 was analyzed by using a double luciferase reporter system,the results showed that PLATZ5 had transcriptional inhibitory activity.(4)When treated with 100 mM and 150 mM Na Cl,the shoot fresh weight of AtPLATZ5 overexpression lines was reduced by 30% and 50%,respectively,while the root fresh weight was reduced by 20% and 18%,indicating the shoot of AtPLATZ5 overexpression lines were more sensitive to salt stress.When the concentration of NaCl was increased to 200 mM,the survival rate of overexpression lines was significantly lower than that of wild type(Col-0).This indicated that AtPLATZ5 negatively regulates seedling resistance to salt stress.AtPLATZ5 overexpression lines also showed a weakly sensitive to 100 mM NaNO3,100 mM KCl and 100 mM KNO3 stress,meanwhile the overexpressing was more sensitive to 10 mM LiCl than 200 mM mannitol.These results indicated that AtPLATZ5 mainly responds to ion stress.(5)The platz5 mutant caused by T-DNA insertion had no different phenotype from WT under salt stress,indicating the function redundance among members of PLATZ family under salt stress.(6)The results of sodium ion probe staining showed that the accumulation of Na+ in the roots of the overexpression lines was increased under salt stress,indicating the influence of sodium uptaking and transporting in the overexpression lines.(7)Analysis expression of marker genes related to SOS signaling pathway indicated that SOS3/CBL4 and its homologous gene CBL10 were significantly downregulated in AtPLATZ5 overexpression lines than WT under salt stress,Ch IP-PCR showed that PLATZ5 targets the SOS3 promoter,suggesting that PLATZ5 responds to salt stress by inhibiting the expression of SOS3.