| The tea resources in Jiangxi Province are distributed in the main tea producing counties,with a large number and rich resources,but their collection,evaluation and utilization are relatively lagging behind.Camellia sinensis‘Huangjinju’is a unique photosensitive etiolated tea variety in Jiangxi.It has excellent tea quality,strong adaptability,large planting area and wide planting range.The current researches on the etiolation mechanism of C.sinensis are mainly focused on the varieties of‘Huangjinju’,‘Zhonghuang 1’,‘Baijiguan’,and‘Yujinxiang’,while there have been no reports of the‘Huangjinju’.In this study,based on the collection and evaluation of tea germplasm resources in Jiangxi Province,we revealed the etiolation mechanism of the new shoots in C.sinensis‘Huangjinju’using analysis of phenotypic traits,physiology and biochemistry,ultrastructure,transcriptome,and non-target metabolome.Results from this study provide data support for the registration and promotion of‘Huangjinju’cultivar,and improvement of the tea yield and quality,and lay a foundation for further developing the tea industry in Jiangxi.The main results are as follows.1.A total of 1,320 tea tree resources in 13 counties of four major tea producing areas in Jiangxi Province were investigated,and more than 260 were collected at the same time.Based on recording,classification,identification and evaluation,the distribution characteristics of tea tree resources in Jiangxi Province were clarified.We then analyzed41 tea tree resources for phenotypic traits,biochemical component,and genetic diversity.Among them,more than 10 specific varieties,‘Xiushui’（XS2）,Fuliang Chuyeqi（PZY3）,‘Fuliang1’（FL1）,‘Chongyi Yangling 1’（CY1）and‘Chongyi Ledong 1’（CY2）with high water extract（≥45%）,‘Chongyi Hekou 1’（CY3）and‘Chongyi Tangjiangshan 1’（CY4）with low tea polyphenols（≤15%）,‘Shangrao Damianbai’（YS1）,‘Yanshan Tongmuguan1’（YS2）,‘Yanshan Xikeng 1’（YS3）and‘Yanshan Caicha’（YS4）with high EGCG（≥12%）,and the chlorotic variety‘Huangjinju’（PZY1）,were obtained.2.Botanical characteristics,adaptability and quality of the specific variety‘Huangjinju’were analyzed.The results showed that it has strong resistance to cold,drought and insect with good adaptability（≥90%survival rate）and is suitable for making green and black tea,which could be popularized in Jiangxi.‘Huangjinju’is highly sensitive to light.After 30 days of shading,the leaves turned green,with a significant increase in SPAD value and chlorophyll content.It was observed by transmission electron microscope that the etiolated leaves had abnormal chloroplast with volume expansion and cystic vacuoles.After shading,the leaf area became larger,the leaf layer thicker,as well as the fresh leaf biomass and the content of amino acids（mainly glycine,citrulline,methionine）and water-soluble lixivium higher.In addition,the content of carbohydrate,catechin,epicatechin and epicatechin gallate decreased significantly and so did some aroma components,such as trans-3,7-Linalool oxide I,1-Hexanol,cis-Hexanoate acid-3-hexene ester,Nonanal,Linalool oxide II（furan type）,1-Pentanol,2,6,6-Timethylcyclohexanone,1-Octanol,β-Linalool,6-Methyl-5-heptene-2-one,Linalool oxide I（furan type）,Naphthalene,Mesityl oxide,3-Hexen-1-ol and Methyl dimethylvalerate.These results suggested that nature sunlight impeded the synthesis process of chlorophyll and disrupted the metabolic balances of carbon and amino acid,leading to the synthesis of different metabolites and the formation of chlorotic shoots in‘Huangjinju’variety.3.Photosynthesis of C.sinensis‘Huangjinju’was analyzed by using shading treatment and variety comparison（with‘Ningzhou 2’as the control）.The results showed that the photosynthetic rate(2.20μmol·m-2·s-1)and value of light parameter Fv/FM（0.63）of natural sunlight‘Huangjinju’（NS）leaves were significantly lower than that of shading treatment（S）and‘Ningzhou 2’（CK）,while the light compensation point(303.00μmol·m-2·s-1)was significantly higher than the S and CK groups.It indicates that the etiolation in C.sinensis‘Huangjinju’might be attributed to the weak photosynthesis,which is affected by the genotype and environment.4.Transcriptome between C.sinensis‘Huangjinju’groups of NS（with etiolated shoots under natural sunlight）and S（with green leaves under shade）was compared.As a result,a total of 507 differentially expressed genes were obtained,of which 198 were up-regulated while 309 were down-regulated in NS vs S.The most significantly up-regulated（9.4 fold）gene was WRKY30（WRKY DNA-binding protein 30）,while the most significantly down-regulated（111 fold）gene was CYP（cytochrome P450）.The gene with the greatest absolute change was LHCB（light-harvesting chlorophyll protein complex II）,followed by LIP（light-induced protein）.The pathway enrichment analysis revealed two pathways that may be involved in the shoot etiolation.One is photosynthesis-antenna protein（ath00196）,in which the expressions of light-harvesting complex I chlorophyll a/b binding protein genes（LHCA2 and LHCA4）and light-harvesting compoundⅡchlorophyll protein genes（LHCB1,LHCB2 and LHCB6）under shade were significantly higher than those under sunlight.The other is protein processing in endoplasmic reticulum（ath04141）.There are 33 genes involved,of which HSP17.6Ⅱ,HSP40,HSP70,HSP90,PDI,NEF,Bi P,and GRP94 were significantly down-regulated,while Derlin,SAR1 and BAP31 were up-regulated.Moreover,the up-and down-regulation of transcription factors such as MYB,b HLH,NAC,WRKY,ERFs and b ZIP might regulate the etiolation process.5.Non-targeted metabolome between C.sinensis‘Huangjinju’groups of NS and S was compared and the different metabolites between them were mapped to the KEGG metabolic pathway.It was found that shading might significantly affect the flavonoid biosynthesis pathway（map00941）,in which coumayl formed chalcone catalyzed by chalcone synthase,then converted to flavanone substances,and eventually formed leuco anthocyanins under the catalysis of anthocyanin synthase,dihydroxyflavonol and4-reductase.We found that CYP,HSP60,HSP70,HSP 90,NEF,HSP 17.6Ⅱ,Derlin,HSP17.4 and HSP21 were highly correlated with this pathway in metabonomic and transcriptomic association analysis.Results here showed that accumulation of metabolites by the flavonoid biosynthesis pathway might be one of the reasons for the shoot etiolation in C.sinensis‘Huangjinju’. |
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