College of Horticulture and Forestry, Huazhong Agricultural University and Key Laboratory of Horticultural Plant Biology, Ministry of Education, Wuhan, 430070, PR China.
Plant Physiol Biochem. 2019 Dec;145:107-113. doi: 10.1016/j.plaphy.2019.10.034. Epub 2019 Oct 24.
Hexose transporters play many important roles in plant development. However, the role of hexose transporter in secondary cell wall growth has not been reported before. Here, we report that the hexose transporter gene CsHT3 is mainly expressed in cells with secondary cell walls in cucumber. Spatiotemporal expression analysis revealed that the transcript of CsHT3 mainly accumulates in the stem, petiole, tendril, and peduncle, all of which contain high cellulose levels. Immunolocalization results show that CsHT3 is localized at the sclereids in young peduncles, shifts to the phloem fiber cells during peduncle development, and then shifts again to the companion cells when the development of secondary cell walls is almost completed. Carboxyfluoresce unloading experiment indicated that carbohydrate unloading in the phloem follows an apoplastic pathway. Overexpression of CsHT3 in cucumber plant can improve the cellulose content and cell wall thickness of phloem fiber cells in the peduncle. The expression of cellulose synthase genes were increased in the CsHT3 overexpression plants. These results indicated that CsHT3 may play an important role in cellulose synthesis through promoting the expression of cellulose synthase genes.
己糖转运蛋白在植物发育中发挥着许多重要作用。然而，己糖转运蛋白在次生细胞壁生长中的作用以前尚未报道。在这里，我们报告己糖转运蛋白基因 CsHT3 主要在黄瓜具有次生细胞壁的细胞中表达。时空表达分析显示，CsHT3 的转录本主要积累在茎、叶柄、卷须和花梗中，这些组织都含有高水平的纤维素。免疫定位结果表明，CsHT3 定位于幼花梗的石细胞中，在花梗发育过程中转移到韧皮纤维细胞，然后在次生细胞壁发育几乎完成时再次转移到伴胞。羧基荧光素卸载实验表明，韧皮部中的碳水化合物卸载遵循质外体途径。在黄瓜植株中过表达 CsHT3 可以提高花梗中韧皮纤维细胞的纤维素含量和细胞壁厚度。CsHT3 过表达植株中纤维素合酶基因的表达增加。这些结果表明，CsHT3 可能通过促进纤维素合酶基因的表达在纤维素合成中发挥重要作用。
