| Tea plant(Camellia sinensis(L.)O.Kuntze)is an important agricultural economic crop in China.Leaves of tea plant are used as raw materials in the processing of non-alcoholic beverages.The germination of buds and the development of young leaves of tea plant are susceptible to the influence of the external environment and endogenous hormones.Tea plant can regulate endogenous hormones to resist high and low temperature stresses.Auxin is one of the most basic endogenous hormones that regulate plant growth and development.Auxin plays an indispensable role in leaf development and morphogenesis of higher plant.The auxin metabolism pathway is mainly composed of auxin synthesis,polar transport,and signal transduction.In this paper,the C.sinensis cv.’Longjing 43’ was used as material.The samples are mainly divided into two kinds,one is the leaves of three developmental stages(first leaf,second leaf,third leaf),and the other is the leaves under different temperature treatments(high temperature 38℃ and low temperature 4℃).The auxin content and cell anatomy of the samples were measured and observed.The regulation effects of auxin synthesis and signal transduction related genes on tea leaf development were dectcted and analyzed.The main results are as follows:1.In this study,a CsBAPl gene was cloned from the cDNA of ’Longjing 43’ based on the transcriptome data of tea plant.Its protein sequence characteristics were analyzed and the gene expression patterns were detected.In addition,the expression profiles of the CsBAPl gene in different tissues and under high/low temperatures and hormone treatments in tea plant was analyzed by RT-qPCR.(1)Sequence analysis showed that the length of the CsBAPl open reading frame(ORF)is 543 bp,encoding 180 amino acids and contains a highly conserved region called C2 domain.Protein analysis suggested that the CsBAP1 is a hydrophilic protein with the theoretical relative molecular weight 19398 Da and the theoretical isoelectric point 9.30.Secondary structure prediction showed that the CsBAP1 protein consists of 8.89%α-helix,7.78%β-turn,35.56%extended strand and 47.78%random coil.The predicted three-dimensional structures indicated that CsBAP1 protein contains α-helix and β-strands.(2)The expression profiles of the CsBAP1 were detected in flower,floral buds,young leaves,mature leaves and senescent leaves by the RT-qPCR.The highest expression level was detected in the mature leaves.The expression level of CsBAP1 was down-regulated by ABA,IAA,MeJA,GA3,and SA treatments,respectively.The expression level of CsBAP1 was up-regulated under high temperature(38℃),low temperature(4℃),drought(200 g·L-1 PEG 6000),and high-salinity(200 mmol·L-1 NaCl)treatments,respectively.These results provide a foundation for the function study of CsBAP1 gene in tea plant.2.To explore the molecular mechanism of IAA metabolism in leaves of tea plant,the leaves samples were collected from the three different development stages of tea plant.Cell morphology and IAA contents were detected and investigated during leaves development.The results showed that the auxin content gradually decreased in three developmental stages.A total of 16 genes involved in IAA biosynthesis and signal transduction pathways were identified based on the genome sequence of C.sinensis,CsTSA,CsIAA27,CsTIR1 and CsCH3-6 expression patterns exhibited positive correlation with IAA concentration in leaves of tea plant.In contrast,CsYUC1,CsCYP83Bl and CsLAX1 transcriptions were negatively correlated with IAA contents during leaves ripening of tea plant.The interaction of IAA metabolism related proteins was also discussed.The results indicated that the growth and development of leaves could be regulated by IAA metabolism in the form of related-genes differentially expression and protein-protein interaction in tea plant.3.This study measured the auxin content and cell section structure of leaves under high and low temperature treatments in tea plant.The results showed that the content of auxin increased significantly at 4 h under high and low temperature treatments,and then gradually decreased.The content of auxin increased again at 48 h under low temperature treatment.The expression patterns of 16 auxin metabolism-related genes in leaves of tea plant under high and low temperature treatment were detected by RT-qPCR.The results displayed that under high temperature treatment,the expression profiles of CsTSB,CsYUC1,CsCYP83B1 and CsARF3 were similar,increased first and then gradually decreased to stabilize.The transcription level of CsNIT2 gradually increases as the processing time increases.Under low temperature treatment,13 genes showed a consistent expression trend,all of which increased first and then decreased.CsGH3-6 was obviously expressed at 48 h under high and low temperature treatments. |
