Study On Physiological And Biochemical Characteristics And Transcriptome Differences Of Tea Plants Under Fluoride Stress

Tea plants are fluorine-rich plants,More than 90%of the fluorine is mainly found in tea leaves.Drinking tea is one of the main ways people take in fluorine.Fluorine is an essential element for the human body,and proper intake is beneficial to the human body,but long-term excessive intake will endanger health.At present,the molecular mechanism of fluorine accumulation in tea plants is still unclear.In this study,hydroponic low-polyfluoride and high-polyfluoride tea varieties were used as experimental materials to study the distribution of fluorine in tea leaves and the physiological and biochemical characteristics of tea plants under different concentrations of fluorine stress;through transcriptome difference analysis,in order to clarify possible tea plants The fluorine-enrichment mechanism provides a theoretical basis for the research on the regulation of fluorine content in tea plants.The main research results are as follows:1.Using the fluorine selective electrode method,the difference of fluorine content in different varieties,different seasons and different leaf positions of tea trees was studied.The fluorine content of one bud and five leaves in spring of 27 tea tree varieties(lines)was determined for five consecutive years.Among them,Xiangbolv(XBL)belongs to a low polyfluoride tea tree variety,which average value of fluorine content in spring is 96.0±13.9mg/kg.Zhenong139(ZN139)is a high-polyfluoride tea tree variety,with an average fluorine content of 198.7±56.6 mg/kg in spring.The order of fluorine content in one bud and five leaves of XBL in different seasons is summer>autumn>spring,and the order of fluorine content in ZN139 one bud and five leaves is summer>spring>autumn.The fluorine content of XBL and ZN139 in different leaf positions were all:fifth leaf>fourth leaf>one bud and one leaf,and XBL had the lowest fluorine content in spring,only 42.7±24.8 mg/kg.2.Hydroponics was used to study the effects of fluoride stress on the growth,catechin composition,pigment content and antioxidant enzyme activity of XBL and ZN139 leaves and roots.The results showed that XBL under low concentration of fluorine stress(10 mg/L),the growth of leaves and roots was inhibited,and as the concentration increased,the leaves appeared crimson spots,and the root growth was significantly inhibited;while ZN139 only showed slight yellow leaves phenomenon under high-concentration fluorine stress(50mg/L),but the root growth is significantly enhanced.Under different concentrations of fluorine stress,the contents of ester-type catechins(EGCG),simple catechins(EGC,DL-C,EC),caffeine,chlorophyll a,chlorophyll b and carotenoids in ZN139 were significantly higher than in XBL In the content.High fluorine treatment resulted in a decrease in Fv/Fm.The XBL treatments were higher than the control,and the ZN139treatments were lower than the control.It proved that the heat dissipation of XBL was increased and the light energy utilization efficiency was reduced under the appropriate amount of fluorine stress,while ZN139 was the opposite.Under the high concentration of50mg/L fluorine stress,the SOD activity in the roots of XBL remained basically unchanged,while the activity of SOD in the roots of ZN139 decreased significantly,but it was still significantly higher than that of XBL.With the increase of fluorine concentration,the difference of POD activity among varieties is significant.3.Using high-throughput sequencing technology to study the expression differences of XBL and ZN139 transcriptomes under fluorine stress.The results showed that when there was no fluoride stress,4558 genes were up-regulated and 4,932 genes were down-regulated in ZN139 relative to XBL in roots;in the first and fifth leaves,2949 and 3168 genes were up-regulated,4211 and 4606,respectively.Down-regulated expression of each gene.Analysis of intraspecific expression differences before and after fluoride stress:After XBL was treated with 10 mg/L and 50 mg/L fluoride solutions,relative to the gene expression level of 0mg/L,there were 2947 common up-regulated genes in roots,1163 Gene-specific up-regulation of expression after 10 mg/L fluoride solution treatment,and 841 genes that were specifically up-regulated expression after 50 mg/L fluorine solution treatment.After the first leaf was treated with two concentrations of fluorine stress,the 5th leaf had few up-regulated genes after the fluorine solution treatment.After the fifth leaf of XBL was treated with two concentrations of fluoride solution,586 genes had the same down-regulated expression pattern,91 genes were specifically down-regulated after 10 mg/L fluoride solution treatment,and 662 genes were specifically down-regulated.The expression was down-regulated after treatment with 50 mg/L fluoride solution.Unlike XBL,ZN139 has only a small number of response genes under fluorine stress,especially in roots.Through the statistics and analysis of the number of differentially expressed genes,it can be found that XBL responds significantly to fluorine stress treatment,and has more differentially expressed genes than in a non-fluorine stress environment;when the fluorine treatment concentration is50 mg/L,XBL's The fifth leaf has more response genes;when ZN139 is in the two concentration environments of 10 mg/L and 50 mg/L,the response genes in the same tissue are quite different,only 3-34 unequal genes have the same The number and proportion of genes with the same expression trend under different concentration treatments in XBL are very high,especially in roots and the 5th leaf.4.Research on the polyfluoride mechanism of different tea varieties.High-polyfluoride tea varieties represented by ZN139 have strong active oxygen scavenging ability under normal environment,low fluoride and high fluoride stress,and in order to maintain the Mg²⁺and photosynthesis that affect photosynthesis.The normal transportation and absorption of Al³⁺reduces the photoprotective ability of converting light energy into heat energy,thereby ensuring that the body maintains a normal photosynthesis rate when it contains a large amount of fluorine.The antioxidant enzyme activity of oligofluoride varieties such as XBL will be significantly induced by low fluoride stress.However,compared with high fluoride varieties,the three tissues have relatively weak active oxygen scavenging ability under different degrees of fluoride stress.The continuous accumulation of reactive oxygen species(ROS)caused by fluoride stress also affects the content of chlorophyll a and other plant pigments.A large amount of photosynthetic energy is converted into glucose to provide energy for the stress of XBL,and at the same time inhibit the germination and elongation of pollen.,Which eventually led to the slowdown of the body's vegetative growth rate and the occurrence of self-incompatibility.A response model of high-and low-fluoride tea varieties to fluoride stress was established,which explained the reasons why high-polyfluoride varieties can maintain good vegetative growth and reproductive growth under high-fluorine stress environments,and low-polyfluoride varieties under fluorine stress The dynamic balance of growth,reproduction and resistance is constructed under the environment.5.The ZFHD transcription factor family member CSA027659,which is relatively highly expressed,responds significantly to fluorine and has high predicted PPIs,was selected for yeast two-hybrid assays to fish for its reciprocal transcription factors.84 clones were screened,and after removing repetitive sequences,a total of 11 candidate positive reciprocal proteins were identified,including two E3 ubiquitin protein ligases ZFP1(XM?028219573.1,XM?028219574.1 028219573.1,XM?028219574.1)with the nuclear localization protein:b HLH107 transcription factor(XM?028207487.1).