Differences In Response To Heat Stress Of Chinese Cabbage With Different Heat Tolerance

The cabbage first originated in China and is widely distributed in various geographical regions of China.High temperature is an important factor that affects the yield and quality of Chinese cabbage.How to improve the heat-resistance of Chinese cabbage and realize the annual supply of Chinese cabbage has become a major problem in the research of Chinese cabbage breeding.Under high temperature stress,heat shock transcription factor(HSF)increases the heat resistance of plants by activating the expression of heat-resistance related genes,To explore the physiological and biochemical mechanisms of Chinese cabbage to adapt to heat stress and the heat-resistance molecular mechanism of HSF of Chinese cabbage will contribute to the normal development of Chinese cabbage under high temperature conditions,Which will provide molecular and physiological basis for heat-resistant breeding of Chinese cabbage and carry out related research has a certain degree of theory and application value.The results of this study are as follows: 1 Analysis of morphological and physiological indexes of Chinese cabbageIn this experiment,two Chinese cabbage inbred lines 2013-33 and Am160 planted in the experimental field of the Academy of Agricultural Sciences were selected as experimental materials,and physiological and biochemical indexes were measured when 5-7 true leaves of Chinese cabbage were grown.The main findings are as follows:From the aspect of appearance,Am160 was inhibited from growing under high temperature stress in summer and could not be broiled;while 2103-33 grew well and could bear the ball.The cytoplasmic membrane permeability showed that the cytoplasmic membrane permeability of Am160 was significantly higher than that of 2103-33 during the summer heat stress,which was significantly higher in summer than in autumn.In summer and autumn,two Chinese cabbage varieties with different heat tolerances showed different adaptive changes in their physiological and biochemical characteristics.Compared with the suitable temperature conditions in autumn,the soluble sugar content of two Chinese cabbages under high temperature stress in summer was higher than that in autumn.High concentration of sugar had certain protective effect on Chinese cabbage under high temperature stress.Under summer heat stress,the protein content of 2013-33 was higher than that of autumn,while that of Am160 was lower than that of autumn.This may be one of the reasons for the high temperature of 2013-33.The osmotic content of osmotic adjustment substances and the tendency of antioxidant enzymes(POD,CAT,and SOD)to remain unchanged or slightly decrease indicate that they have little effect on the heat resistance of Chinese cabbage.2 Analysis of photosynthetic characteristics of Chinese cabbage.The main difference in photosynthetic efficiency between the seedlings of two Chinese cabbages in autumn is the ?Vt curve of chlorophyll fluorescence kinetics.The J and L phases of AM160 cabbage were relatively higher than those of 2013-33,while the cabbages of AM160 cabbage were shown on the ?Wt curve.There was no significant difference in the density and activity of photoreaction centers between the two Chinese cabbages.The above phenomenon was mainly caused by the fact that the mass bank of AM160 was smaller than that of 2013-33,resulting in lower photosynthetic performance index(PI)and photosynthetic rate(Pn)than 2013-33.Under high temperature conditions in summer,the difference between the two is very similar to autumn,except that the difference in performance index and net photosynthetic rate of the two Chinese cabbages is greater,and the increase in heat dissipation is more pronounced.Therefore,the size of the plastopod banks may be the main difference in the heat resistance of the photosynthetic systems of the two Chinese cabbages.3 Analysis of Expression Pattern of HSF Gene in Chinese CabbageIn this study,34 HSF family genes were identified from the Chinese cabbage genome.RT-qPCR was used to analyze the expression pattern of Chinese cabbage seedlings after heat treatment for different time.The seedling stage was heat treated at 38 ? for 0 h,1 h and 3 h respectively.Compared with 0 h,the expression levels of Bra021381,Bra000235,Bra00557,Bra023584 and Bra007739 in 2013-33 and Am160 were all increased after heat treatment for 1 h;The expression level of Bra012828 in 2013-33 and Am160 was reduced;Bra040179,Bra001071,Bra001885,Bra012829,Bra040968,Bra009515,and Bra013358 were up-regulated in 2013-33 but down-regulated in Am160;Bra029292,Bra029291,Bra000749,and Bra032752 were down-regulated in 2013-33 and up-regulated in Am160 with significant changes.After heat treatment for 3h,Bra021381,Bra012828,Bra40179,Bra010171,Bra001885,Bra012829,and Bra040968 were up-regulated in 2013-33 but down-regulated in AM160;Bra23584,Bra007739 and Bra009515 were up-regulated between the two varieties;Bra029292,Bra000749,and Bra032752 were downgraded in 2013-33 and AM160 was raised;In addition,Bra000557 did not change much.Bra013358 did not change much in 2013-33,but in AM160,Bra029291 decreased in 2013-33,but the expression in AM160 remained unchanged.In summary,Bra040179,Bra010171 and Bra040968 may play an important role in the heat-resistance of Chinese cabbage based on the changing trend of expression levels.4 Sequence Difference of BrHSFs Genes in Two Chinese CabbageUsing the cDNAs of heat-resistant material 2013-33 and heat-labile material AM160 as templates,all members of the HSF gene family of Chinese cabbage were cloned,and the sequence differences between the heat-resistant and heat-resistant Chinese cabbage varieties of each member were compared.Among the HSF family members that have been sequenced,Bra004272 has sequence differences in the promoter regions of two heat-resistant Chinese cabbage inbred lines,Bra0015050 differs in the CDS area of cabbage inbred lines with different heat tolerances,Compared with 2013-33,AM160 had a deletion of about 8 bp,and Bra008593 had a difference in both the promoter region and the CDS region.5 Analysis of the Linkage between the Sequence Difference and Heat Tolerance of Two Chinese Cabbage BrHSFs GenesAccording to the analysis of the sequence differences of two heat-resistant cabbages of Chinese cabbage HSF family members,the differential sequences were found.Then the primers were designed based on the sequenced differential sequences as a template and verified in F2 populations of two heat-tolerant Chinese cabbages.It was found that the measured differential genes were not linked to the heat tolerance of Chinese cabbage.