Study On The Effect Of BnMAPK1 On The Tolerance Of Brasscia Napus Against Temperature Stress And The Corresponding Mechanism

As the third largest oil crop in the world,oilseed rape is one of the main sources of vegetable oil.The planting area and output in China can reach one-third of the world,ranking the first in the world.It plays a vital role in the national edible oil safety strategy.However,high or low temperature stresses during the growth period of rapeseed affects the yield and quality of rapeseed.Therefore,breeding stress-resistant varieties of rapeseed is of great significance for improving the yield and quality of rapeseed.Mitogen-activated protein kinases(MAPKs)are a class of serine / threonine protein kinases in eukaryotes and have evolutionary conserved signaling modules in basic regulatory functions.The MAPK cascade can respond to biotic or abiotic stress-related pathways in a variety of plants,influcing the growth and development processes.The former study indicated the overexpression of BnMAPK1 improved the tolerance on B.napus against high temperature.In this study,we tested the influence and the corresponding mechanism of BnMAPK1 on the tolerance of B.napus against high and temperature stress,using the Zhongyou 821 as experimental materials.The main results are as follows:1.Overexpression of BnMAPK1 affected the physiological characteristics of B.napus under low temperature treatmentThe overexpression and wild-type lines with consistent growth conditions were treated at 4 ℃.The dynamic changes of chlorophyll,proline,soluble sugar,malondialdehyde content and antioxidant enzyme activities(SOD,POD,CAT)were detected.The results showed that overexpression of BnMAPK1 can slow down chlorophyll degradation,promote the accumulation of proline and soluble sugar,reduce the content of malondialdehyde,and enhance the activity of antioxidant enzymes(SOD,POD,CAT)to some extent.2.Molecular mechanism underlying tolerance of B.napus against low termperatureIn order to further study the molecular mechanism underlying the improvement efffect of BnMAPK1 on the cold tolerance in B.napus,the leaves from the overexpression and wild type lines under low temperature treatment were collected for transcriptome sequencing.Transcriptome analysis showed that under low temperature stress,the stimulus response pathways such as hormone signal transduction,photosynthesis,biosynthesis or metabolism of organic matter(secondary metabolites)are stimulated and regulated in B.napus,and they may be intertwined and work together.That is to say,the regulation pathway of rape under low temperature is complicated.3.Overexpression of BnMAPK1 improves the tolerance of B.napus against low temperatureTranscriptome sequencing showed that overexpression of BnMAPK1 can improve the cold tolerance of B.napus.BnMAPK1 may be involved in cell,metabolism,and development processes,including photosynthetic pathway regulation,root system,organ growth and development regulation,material metabolism,ribosomal biogenic activity,etc.Overexpression of BnMAPK1 changes the expression of 45 genes,showing that BnMAPK1 may promote the photosynthetic capacity and the transport of photosynthetic products,promote protein degradation and protein synthesis under low temperature stress,and reduce the synthesis of some hydrolases,transferases,flowering promoting proteins,and so on.In addition,many transcription factors are significantly enriched in low-temperature response genes of overexpressed materials and genetically differentially expressed genes between the two materials,including 161 transcription factor genes that specifically respond to overexpressed materials and 118 transcription factor genes that are genetically differentially expressed between the two materials,they are concentrated in bHLH,AP2/ ERF-ERF,WRKY,bZIP,GARP-G2-like,MYB,C2C2-GATA and AP2 / ERF-ERF,MYB,WRKY,bHLH,HB-HD-ZIP,MYB-related,NAC family.This indicates that BnMAPK1 protein may regulate these transcription factors at low temperature,and they jointly participate in the low-temperature signaling pathway,which may be useful in low-temperature breeding of rapeseed.4.Overexpression of BnMAPK1 improves the tolerance of B.napus against high temperatureIn order to further study the molecular mechanism of BnMAPK1 to improve the heat resistance of B.napus,overexpression and wild-type rape lines were exposed to high temperature treatment(40℃),and then the leaves of the same parts were collected for transcriptome sequencing.It was found that under high temperature stress,a large number of stress-response pathways in B.napus were changed,including metabolic development and stimulus response are stimulated.At the same time,processes and pathways such as ribosomes,protein synthesis,protein processing in the endoplasmic reticulum,and translation play an important role.That is,a large amount of protein synthesis,processing and metabolism have a key role at high temperature.5.The molecular mechanism underlying improvement effect of BnMAPK1 in the heat resistance of B.napusTranscriptome sequencing found that overexpression of BnMAPK1 can improve the tolerance against high temperature through metabolic development and stimulus response.Among them,it is mainly related to the synthesis of organic matter.BnMAPK1 promotes the role of proteasome in the response of rape to high temperature.BnMAPK1 may cause protein metabolic regulation.Overexpression of BnMAPK1 changes the expression pattern of 211 genes,and it indicated that BnMAPK1 may inhibit the expression of WRKY7(Bna A03g46550D),WRKY33(Bna Cnng66020D),WRKY33(Bna A04g22040D),and promote early light-induced protein(Bna A01g24440D),DNA mismatch repair protein Expression of MSH1(Bna A07g05700D).In addition,many transcription factors were significantly enriched in the over-expression material high-temperature response genes and the genetically differentially expressed genes between the two materials,including 334 transcription factor genes that specifically responded to the over-expression material and 221 genetically differentially expressed between the two materials Transcription factor genes,which are concentrated in AP2 / ERF-ERF,bHLH,MYB,bZIP,C2H2,GARP-G2-like and MYB,AP2 /ERF-ERF,bHLH,NAC,HB-HD-ZIP,HSF families.They may be regulated by the BnMAPK1 protein under high temperature treatment,and participate in the high temperature response pathway in B.napus and work together,and may have utility value in high temperature breeding of B.napus.