黄瓜糖转运蛋白SWEET调控蔗糖在绒毡层质外体卸载的分子机制

花粉在植物有性生殖中具有重要作用，其发育过程中需花药绒毡层向其提供大量糖分，若糖分供应或转运受阻会导致花粉发育异常甚至败育，严重降低农作物果实或种子的产量及品质。研究表明，绒毡层细胞内的糖分采用质外体途径卸载到花粉细胞，此过程第一个关键步骤需糖转运蛋白SWEET参与。黄瓜是重要的经济园艺作物，但目前对糖分从黄瓜绒毡层卸载到花粉的分子机制知之甚少。前期实验结果表明，黄瓜蔗糖转运蛋白基因CsSWEET12可能在此过程中具有重要作用。本项目拟运用酵母异源表达、免疫组化、原位杂交、原生质体瞬时表达、免疫胶体金定位等技术对CsSWEET12进行糖吸收、时空表达、组织及亚细胞定位分析；通过黄瓜转基因技术验证CsSWEET12生物学功能，并从代谢组学水平解析其对花粉发育代谢网络的影响。最终明确CsSWEET12是否参与蔗糖在黄瓜绒毡层的质外体卸载及其作用机制，为黄瓜果实、种子优质高产提供重要的理论依据。

Pollen plays an important role in plant sexual reproduction. It is well accepted that pollen needs large amounts of sugars that are supplied by the tapetal cells to fuel its development. As a consequence of such a high sugar demand during pollen development, any perturbation of either sugar supply or transport capability results in irreversible impairment to the pollen development and usually results in male sterility, so largely reducing the yield and quality of crop fruit or seed. Previous studies have shown that sugar unloading from tapetum cells to pollen cells by an apoplastic unloading pathway, and the first critical step of this process relies upon the sugar transporter SWEET. Cucumber is one of the most important economic horticultural crops. However, the molecular mechanism of sugar unloading from tapetum tissues to pollen cells in cucumber is poorly understood. Our preliminary experimental results indicated that the sucrose transporter CsSWEET12 may play an important role in the process. In this study, using a combination of yeast heterologous expression, immunolocalization, in situ hybridization, protoplast transient expression and immunogold localization, the sugar transport characteristic, spatiotemporal expression, tissue and subcellular localization of CsSWEET12 will be studied. Moreover, the biological function of CsSWEET12 will be verified by cucumber transgenic technology. In addition, the effect of CsSWEET12 on the metabolic profiles during cucumber pollen development will also be analyzed using the metabolomics strategy. These results will determine whether CsSWEET12 is involved in sucrose apoplasmic unloading in the tapetum tissues of cucumber, as well as its mechanism. Our data will give important theoretical basis for improving the yield and quality of cucumber fruit or seed.