Abstract
Drought stress often affects the expression of genes and proteins in tea plants. However, the global profiling of ubiquitinated (Kub) proteins in tea plants remains unearthed. Here, we performed the ubiquitome in tea leaves under drought stress using antibody-based affinity enrichment coupled with LC-MS/MS analysis. In total, 1,409 lysine Kub sites in 781 proteins were identified, of which 14 sites in 12 proteins were up-regulated and 123 sites in 91 proteins down-regulated under drought stress. The identified Kub proteins were mainly located in the cytosol (31%), chloroplast (27%) and nuclear (19%). Moreover, 5 conserved motifs in EKub, EXXXKub, KubD, KubE and KubA were extracted. Several Kub sites in ubiquitin-mediated proteolysis-related proteins, including RGLG2, UBC36, UEV1D, RPN10 and PSMC2, might affect protein degradation and DNA repair. Plenty of Kub proteins related to catechins biosynthesis, including PAL, CHS, CHI and F3H, were positively correlated with each other due to their co-expression and co-localization. Furthermore, some Kub proteins involved in carbohydrate and amino acid metabolism, including FBPase, FBA and GAD1, might promote sucrose, fructose and GABA accumulation in tea leaves under drought stress. Our study preliminarily revealed the global profiling of Kub proteins in metabolic pathways and provided an important resource for further study on the functions of Kub proteins in tea plants.
Highlights
Ubiquitination can mark proteins for degradation via the proteasome, alter protein subcellular location, affect their activities, and promote or inhibit protein interactions[10,11,12]
The bands of multiple Kub proteins in control treatment (CK) and drought treatment (DT) were detected and all proteins in DT were reduced by long induction of drought stress, suggesting that the Kub proteins in tea leaves were changed dynamically and the lysine-ubiquitinated peptides could be enriched by di-Gly-Lys-specific antibody
Our results revealed that a large number of Kub proteins in tea leaves were participated in metabolic pathways, including ubiquitin-mediated proteolysis, catechins biosynthesis, and carbohydrate and amino acid metabolism
Summary
Ubiquitination can mark proteins for degradation via the proteasome, alter protein subcellular location, affect their activities, and promote or inhibit protein interactions[10,11,12]. Ubiquitination was associated with DNA damage response, membrane transport and transcriptional regulation, as well took part in enzymatic activity regulation and stress responses[13,14]. The role of ubiquitination in tea plants remains unearthed. To investigate the possible mechanisms of Kub proteins in tea plants under drought stress, we studied the ubiquitome using antibody-based affinity enrichment coupled with LC-MS/MS analysis. We analyzed the GO, KEGG and PPI of identified Kub proteins. Our study preliminarily revealed the global profiling of Kub proteins in metabolic pathways and provided an important resource for further study on the functions of Kub proteins in tea plants
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