Tea plant SWEET transporters: expression profiling, sugar transport, and the involvement of CsSWEET16 in modifying cold tolerance in Arabidopsis
Thirteen SWEET transporters were identified in Camellia sinensis and the cold-suppression gene CsSWEET16 contributed to sugar compartmentation across the vacuole and function in modifying cold tolerance in Arabidopsis.
The sugars will eventually be exported transporters (SWEET) family of sugar transporters in plants is a recently identified protein family of sugar uniporters that contain seven transmembrane helices harbouring two MtN3 motifs. SWEETs play important roles in various biological processes, including plant responses to environmental stimuli. In this study, 13 SWEET transporters were identified in Camellia sinensis and were divided into four clades. Transcript abundances of CsSWEET genes were detected in various tissues. CsSWEET1a/1b/2a/2b/2c/3/9b/16/17 were expressed in all of the selected tissues, whereas the expression of CsSWEET5/7/9a/15 was not detected in some tissues, including those of mature leaves. Expression analysis of nine CsSWEET genes in leaves in response to abiotic stresses, natural cold acclimation and Colletotrichum camelliae infection revealed that eight CsSWEET genes responded to abiotic stress, while CsSWEET3 responded to C. camelliae infection. Functional analysis of 13 CsSWEET activities in yeast revealed that CsSWEET1a/1b/7/17 exhibit transport activity for glucose analogues and other types of hexose molecules. Further characterization of the cold-suppression gene CsSWEET16 revealed that this gene is localized in the vacuolar membrane. CsSWEET16 contributed to sugar compartmentation across the vacuole and function in modifying cold tolerance in Arabidopsis. Together, these findings demonstrate that CsSWEET genes play important roles in the response to abiotic and biotic stresses in tea plants and provide insights into the characteristics of SWEET genes in tea plants, which could serve as the basis for further functional identification of such genes.
KeywordsCold tolerance Gene expression Stress Sugar transporter SWEET Tea plant (Camellia sinensis)
Basic local alignment search tool
Enhanced green fluorescent protein
Expressed sequence tags
Maximal quantum efficiency of photosystem II
Murashige and Skoog
Open reading frame
Reverse transcription PCR
Sugars will eventually be exported transporters
This work was supported by the National Natural Science Foundation of China (31500564), the Young Elite Scientist Sponsorship Program by CAST (2016QNRC001), the Central Public-interest Scientific Institution Basal Research Fund (1610212016006), the Earmarked Fund for China Agriculture Research System (CARS-19) and the Chinese Academy of Agricultural Sciences through an Innovation Project for Agricultural Sciences and Technology (CAAS-ASTIP-2017-TRICAAS). We thank Professor Dr. Eckhard Boles of institut für molekulare biowissenschaften Goethe-Universität Frankfurt for providing yeast strains EBY.VW4000 and Professor Dr. Huixia Shou of Zhejiang University for providing the vectors ADHpr-Yeplac195 and pBI101.3.
LW, XCW and YJY participated in the design and coordination of the study. LW, LNY, XYH, NNL, WJQ, CY, CQD and JMZ performed the experiments. LW, LNY and XCW analyzed and discussed the data. LW and XCW wrote the manuscript. All authors read and approved the manuscript.
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