Functional Studies On Salt Tolerance Of NF-YC Transcription Factor In Populus Davidiana×P.bolleana

Nuclear factor Y(NF-Y)transcription factors are key regulators associated with plant growth and stress resistance.This class of transcription factors regulates a variety of physiological and developmental processes in plants by participating in protein-DNA or protein-protein interactions.However,the functions and mechanisms of NF-Y transcription factors in poplar in response to abiotic stresses are not well understood.In the present study,we identified 26 PdbNF-Y-encoding genes in Populus davidiana×P.bolleana,including 12 PdbNF-YA,6 PdbNF-YB,and 8 PdbNF-YC.the number of amino acids encoded by these PdbNF-Y genes is predicted to range from 217-366,with a theoretical isoelectric point(p I)of5.04-9.69,all of which are hydrophilic proteins.The PdbNF-Y family genes were analyzed by real-time fluorescence quantitative RTq PCR in response to the stress of adversity.The results showed that members of the PdbNF-Y gene family were able to respond to salt and drought stresses as well as induction by the exogenous hormone ABA,suggesting that this family may play an important role in the response to abiotic stresses in Populus davidiana×P.bolleana.Among them,PdbNF-YC7 was significantly up-regulated under all treatments,so PdbNF-YC7 was selected to investigate its function in poplar in response to salt stress in depth.Transient transformation of native tobacco for subcellular localization using injection method showed that PdbNF-YC7 protein was localized in the nucleus.The transcriptional activation activity of PdbNF-YC7 protein was characterized by yeast two-hybrid system,and the results showed that it did not possess transcriptional activation activity.The PdbNF-YC7 overexpression vector was constructed,and the Populus davidiana×P.bolleana strain overexpressing the gene was obtained by transformation with Agrobacterium tumefaciens.The function of PdbNF-YC7 in salt tolerance of poplar was investigated by salt stress treatment,and the results showed that after 5 days of salt stress,the leaves of the overexpression strain were less injured by salt stress compared with the wild type.Meanwhile,the results of physiological and biochemical indexes showed that the overexpression of PdbNF-YC7 increased the enzymatic activity of antioxidant enzymes and proline content in poplar under salt stress,which in turn reduced the accumulation of reactive oxygen species(ROS)and cell membrane damage caused by salt stress.In conclusion,the PdbNF-YC7 gene protects cell integrity by improving the scavenging ability of reactive oxygen species(ROS)in poplar,and thus enhances salt tolerance in mountain new poplar.