| Tea plant[Camellia sinensis(L.)O.Kuntze]belongs to the genus Camellia and is a perennial evergreen woody plant that prefers acid and warm but fears of alkali and cold.Tea plant has been cultivated for thousands of years and is a kind of important economic crop in China.The leaves and buds of tea plant are often used to produce tea,which is rich in tea polyphenols,amino acids,minerals,organic acids,vitamins and other secondary metabolites.It is a natural nutritious health drink.However,tea plant is vulnerable to a variety of abiotic stresses during its lifetime.High temperature,low temperature,drought,and high salt seriously affect the growth and development of tea plant,which affect the yield and quality of tea and affect economic benefits.HD-Zip transcription factors play important roles in plant growth and development,signal transduction,and stress response.Here,based on the genomic and transcriptomic database of tea plant,33 HD-Zip transcription factors were isolated and identified,and their preliminary function were studied.The main results are as follows:1.Based on the genomic and transcriptomic database of tea plant,33 HD-Zip transcription factors were identified and named as Cshdzl to Cshdz33,respectively.Firstly,the phylogenetic tree of these HD-Zip transcription factors was constructed and divided into four groups(HD-Zip Ⅰ,HD-Zip Ⅱ,HD-Zip Ⅲ,and HD-Zip Ⅳ).The largest proportion of these transcription factors was HD-Zip Ⅰ(20 members),up to 61%.Subsequently,conservative domain and sequence analysis showed that HD-Zip conservative domain was typical of plants,while HD-Zip Ⅰ and HD-Zip Ⅱ had more motifs than the other two groups.Compared with other plants,the total number of HD-Zip transcription factors in tea plant was significantly lower than that in other plants.The protein-protein interaction network of HD-Zip between tea plant and Arabidopsis thaliana was constructed.The protein function and interaction relationship of HD-Zip in tea plant were predicted,indicating the complex relationship and functional diversity of transcription factors.Heat map results showed that HD-Zip family genes were expressed in different tea varieties,and the expression level of Cshdz8 gene was significantly higher than that of other Cshdz genes.2.The expression patterns of HD-Zip family genes in tea plant cv.’Longjing43’ under abiotic stresses were detected by RT-qPCR.The results showed that HD-Zip family genes in tea plant respond to five different abiotic stresses:high temperature,low temperature,high salinity,drought and ABA treatments.Under high temperature stress,the expression levels of Cshdz8 and Cshdz7 genes were similar,and increased with the treatment time.The expression level of Cshdz 16 gene was up-regulated and reached the highest level at 8 h,showing a trend of first increasing and then decreasing.The expression levels of Cshdz genes increased significantly under low temperature stress.The gene expression levels of Cshdz6,Cshdz7,Cshdz8,and Cshdz20 increased to the maximum at 2 h,then decreased gradually.However,the Cshdz15 and Cshdz16 genes reached their maximum at 24 h and showed higher expression levels than other genes relative to the control group.Under high salt stress,the expression levels of most Cshdz genes were up-regulated.The expression levels of Cshdz7 and Cshdz8 genes showed the same trend,which increased first,then decreased,and finally reached the highest level at 24 h.The expression levels of Cshdz15,Cshdz16,and Cshdz20 genes were more than 20 times higher than those of the control group,suggesting that they may play an important role in response to high salt stress.Under drought stress,the expression levels of all Cshdz genes were up-regulated and reached the highest level at 24 h.The expression levels of Cshdz6 and Cshdz7 genes were similar,which decreased to the lowest level at 2 h or 4 h,and then increased with the treatment time.With the prolongation of drought treatment time,the expression level of Cshdz8 gene gradually increased,showing an obvious upward trend.Under ABA treatment,the expression level of Cshdz6 gene increased gradually and reached its peak at 4 h.This trend is similar to Cshdz7,Cshdz8,and Cshdz20 genes,and the expression levels of these four genes increase first and then decrease.In addition,the expression levels of Cshdz15 and Cshdz 16 genes showed an upward trend,and reached the maximum at 24 h.3.The effects of high and low temperature stress on Tr,Pn,Ci,and Gs of tea leaves were measured,and the expression levels of five HD-Zip genes related to photosynthesis were also detected and analyzed.The results showed that the photosynthesis of tea plant was significantly inhibited under high and low temperature stress.Among them,the Pn of tea leaves decreased successively to negative values,Tr and Gs also showed a downward trend,negatively correlated with Ci and positively correlated with Pn.The correlation analysis showed that the expression levels of HD-Zip transcription factors were positively correlated with Ci,and negatively correlated with Pn,Tr,and Gs.The expression levels of Cshdz7 and Cshdz8 under high temperature stress were significantly negatively correlated with Pn(-0.947,-0.881)and Tr(-0.915,-0.918).Cshdz15 was significantly negatively correlated with Pn under low temperature stress(-0.982).It is speculated that Cshdz7,Cshdz8,and Cshdz15 may be involved in the regulation of photosynthesis in tea plant. |
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