CsHT11 encodes a pollen-specific hexose transporter and is induced under high level sucrose in pollen tubes of cucumber (Cucumis sativus)
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Pollen tubes require a high amount of sugars to sustain high growth rate. Sucrose, the main transport form of sugars, can serve as energy supply and as signaling molecules for pollen tube growth. We report the functional characterization of CsHT11, which is a sugar transporter protein/hexose transport protein (STP/HT). CsHT11 shares high homology with the characterized cucumber hexose transporter CsHT1, a pollen-specific gene. Analysis of CsHT11 mRNA and CsHT11 promoter-reporter gene studies revealed CsHT11 specifically expressed in pollen and pollen tubes. Subcellular localization indicated that CsHT11 is a plasma membrane transporter. Heterologous expression in yeast suggests that CsHT11 is an energy-dependent hexose/H+ symporter, with a wide variety of substrate specificity, including glucose, fructose, galactose, and mannose. In vitro pollen germination of different sugars shows that the expression of CsHT11 is significantly increased with higher sucrose content, but not with higher glucose or fructose content, thereby implying that CsHT11 may be involved in sucrose signal transduction. Thus, CsHT11 might have an essential effect on pollen development and pollen tube growth in cucumber.
KeywordsHexose transporter Cucumber Male flower Pollen Pollen tubes
Hexose transport protein
Sucrose transport protein
Sugars will eventually be exported transports
Sucrose transport protein
Cell wall invertases
We thank Fareeha Shireen for helpful discussions. This work was supported by the National Key Research and Development Program of China (2019YFD1000300) to Jintao Cheng, the National Natural Science Foundation of China (31972435 and 31601774) to Jintao Cheng and the Fundamental Research Funds for the Central Universities (2662018QD062) to Jintao Cheng.
JTC designed research. JTC and ZLB found the experiments. SYW, TYB and XWZ conducted experiments. SYW analyzed data and wrote the manuscript. All authors read and approved the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
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