Regulation Of Tolerance To Salt Stress By AtFC1 In Arabidopsis Thaliana

Today,20%of the world's cultivated land and nearly half of all irrigated lands are affected by salinity.Salinity is one of the major environmental stresses which seriously causes cellular dehydration and ionic toxicity,thus limiting the productivity of crops.To survive the detrimental effect of high salinity,plants have evolved multiple sophisticated strategies to cope with the adverse stresses via perceiving the stress signal and transmitting the information through a variety of signal transduction pathways and adjustment of their metabolic processes;upon receipt of the signal,a number of molecular and cellular responses are initiated.Ferrochelatase-1(AtFCl,EC 4.99.1.1)is a stress-responsive factor coding for an enzyme catalyzing the insertion of ferrous iron into the macro-cycle of protoporphyrin IX to form protoheme.Although several reports indicate that AtFC1 is involved in Heme biosynthesis,which further regulates a variety of physiological and biochemical processes,its biological role in regulating salt tolerance is poorly understood.We are interested in performing a genetic study to identify a role of AtFC1 in the salt stress response.In this paper,the method of combination of bioinformatics,transgenic technology and plant physiological is used to explore the relationship between AtFC1 and salt stress.From the preliminary analysis of AtFC1 upstream promoter and detection of gene expression changes under salt stress,we presume that AtFC1 takes participate in salt tolerance.To figure out whether AtFCl is able to regulate salt tolerance,AtFC1 over-expressing transgenic plants and AtFCl down regulated mutant(fcl)plants are constructed and identified.The results show that 35S::AtFC1 plants confer plant resistance to salt stress by improving seed germination rate and primary root growth,reducing Na+ accumulation in shoot and root,and preventing K+ loss.In contrast,the AtFC1 loss-of-function fcl mutant results in adverse phenotypes.In addition,exogenous hematin can effectively alleviate tissue damages of fc1 mutant under salt stress.From what has been showed above,we can come to a conclusion that hematin has a protective role under salt stress and over-expression of AtFCl can enhance salt tolerance in Arabidopsis.In order to analyze the position of AtFCl in salt resistance pathway,salt-related genes transcript levels under salt stress are detected.Results show that AtFC1-regulated salt-tolerance is involved in SOS1,SOS2,SOS3,NHX1,AVP1,P5CS1 and RD22 expression.A later experiment also indicates that exogenous hematin can influence Na+ content and SOS1 expression,and the changes of Na+ content can explain the expression changes of SOS1 perfectly.The results indicate that AtFCl may be act upstream of NHX1,AVP1,P5CS1 and RD22 and downstream of SOS1,SOS2 and SOS3 factors that mediated salt stress response.Considering all the experiments above,we can get this conclusion that over-expressing AtFCl can enhance salt tolerance and it is depended on the heme homeostasis and SOS1 transcript level.