Cheng Jintao, Wen Suying, Li Kexin, Zhou Yixuan, Zhu Mengtian, Neuhaus H Ekkehard, Bie Zhilong
National Key Laboratory for Germplasm Innovation and Utilization for Fruit and Vegetable Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, Hubei Province, China.
Plant Physiology, University of Kaiserslautern, Erwin Schrödinger Str., D-67663 Kaiserslautern, Germany.
Plant Physiol. 2025 Feb 7;197(2). doi: 10.1093/plphys/kiae597.
Hexoses are essential for plant growth and fruit development. However, the precise roles of hexose/H+ symporters in postphloem sugar transport and cellular sugar homeostasis in rapidly growing fruits remain elusive. To elucidate the functions of hexose/H+ symporters in cucumber (Cucumis sativus L.) fruits, we conducted comprehensive analyses of their tissue-specific expression, localization, transport characteristics, and physiological functions. Our results demonstrate that CsHT3 (C. sativus hexose transporter), CsHT12, and CsHT16 are the primary hexose/H+ symporters expressed in cucumber fruits. CsHT3 and CsHT16 are localized in the sieve element-companion cell during the ovary and early fruit development stages. As the fruit develops and expands, the expression of both symporters shifts to phloem parenchyma cells. The CsHT16 knockout mutant produces shorter fruits with a larger circumference, likely due to impaired sugar and phytohormone homeostasis. Concurrent reduction of CsHT3, CsHT12, and CsHT16 expression leads to decreased fruit size. Conversely, CsHT3 overexpression results in increased fruit size and higher fruit sugar levels. These findings suggest that CsHT16 plays an important role in maintaining sugar homeostasis, which shapes the fruit, while CsHT3, CsHT12, and CsHT16 collectively regulate the supply of carbohydrates required for cucumber fruit enlargement.
己糖对植物生长和果实发育至关重要。然而，己糖/H⁺同向转运体在韧皮部后糖运输和快速生长果实的细胞糖稳态中的具体作用仍不清楚。为了阐明己糖/H⁺同向转运体在黄瓜（Cucumis sativus L.）果实中的功能，我们对其组织特异性表达、定位、运输特性和生理功能进行了全面分析。我们的结果表明，CsHT3（黄瓜己糖转运体）、CsHT12和CsHT16是黄瓜果实中表达的主要己糖/H⁺同向转运体。在子房和果实发育早期，CsHT3和CsHT16定位于筛管分子-伴胞。随着果实发育和膨大，这两种同向转运体的表达转移到韧皮薄壁细胞。CsHT16基因敲除突变体产生的果实较短但周长较大，这可能是由于糖和植物激素稳态受损所致。同时降低CsHT3、CsHT12和CsHT16的表达会导致果实大小减小。相反，CsHT3的过表达导致果实大小增加和果实糖含量升高。这些发现表明，CsHT16在维持糖稳态中起重要作用，而糖稳态决定了果实的形状，而CsHT3、CsHT12和CsHT16共同调节黄瓜果实膨大所需碳水化合物的供应。
