Analysis Of 7 DREB1 Genes From Panicum Virgatum And Functional Study On DREB1C In Plant Salt Tolerance

Switchgrass(Panicum virgatum)is an important perennial grass used for bioenergy and soil-conservation purposes.Studies on plant stress tolerace mechanism will provide insights on switchgrass improvement for better adaptability on marginal lands and also provide gene resources for the genetic improvement in other crops.DREB/CBF,a vital transcriptional factor family,plays a significant role in plant abiotic resistance,conferring plant tolerance to different abiotic stresses,such as salinity,drought,and cold.This study analyzed seven DREB1 family genes isolated from switchgrass.One such gene,PvDREB1C gene was overexpressed in tobacco.The transgenic tobacco showed significantly improved salt tolerance.The main findings are showed as follows.(1)A total of seven PvDREB1 family genes were isolated from switchgrass.The sequence alignment shows that all these genes contain the conserved AP2 DNA binding domain,nuclear localization signal(NLS)and a DSAW/R sequence that located in the upstream and downstream of AP2 domain.The sepecial LWSY sequence is found in the C-terminal tail.These featured sequences are the typical conserved sequence of DREB1 transcriptional factors.(2)Phylogenetic tree analyzed the seven PvDREB1s and orthologous genes in rice and Arabidopsis.According to the corresponding homologous genes in rice,we named the 7 PvDREB1s as PvDREB1A-1/-2,PvDREB1B-1/-2?PvDREB1C and PvDREB1G-1/-2 respectively.(3)The rd29A promotor and its 4 mutants that contained different numbers of two kinds of DRE cis-elements(ACCGAC/GCCGAC)were obtained by point mutation.The binding activity of 7 PvDREB1s with different rd29A promotors is estimated by measuring the GUS activity,in order that it can evaluate their recognition preference with the different DRE cis-elements.(4)Overexpression of the PvDREB1C improved the salt resistance of tobacco seedlings.Relative to WT plants,the transgenic lines exhibited significantly increased fresh weight,osmotic potential and chlorophyll content.Transgenic plants exhibited reductions in H2O2 and O2-content thanWT in response to salt stress.(5)The transgenic lines display higher FW,plant height,stem width,chlorophyll content,and Fv/Fm than those of WT under 200mM NaCl treatment,and have lower EL.Besides these,the activity of antioxidant enzyme(SOD?POD and APX),the expression level of NtSOD and NtPOD(antioxidant-relatedgene),NtNHX4(Na+/H+ anti transporter gene),NtERD10B(dehydrin gene)in transgenic lines significantly higher than WT.These results demonstrated the PvDREB1C can improve the salt tolerance by regulating the plant tantioxidant system,ion transport and osmotic adjustment.