Phalaenopsis orchids require a prolonged period of low temperatures for flowering, which is highly correlated with soluble sugar contents in leaves. This study was conducted to investigate changes in leaf sugar content during sink transition in Phalaenopsis. Phalaenopsis Queen Beer ‘Mantefon’ clones were grown at 28 °C, followed by exposure to 20 °C for floral induction. Leaves were sampled after 0, 2, 6, and 10 weeks of the low temperature (LT) treatment for analysis of soluble sugar content and RNA-seq. Exogenous sucrose labeled with a stable carbon isotope was applied to mature leaves. Inflorescences did not yet emerge after two weeks, but they were 0.5–1 cm and 5–10 cm long after 6 and 10 weeks, respectively. The carbon isotope analysis revealed that leaf sugars were translocated from leaves to inflorescences during the floral induction, rather than vegetative organs such as newly developing leaves. After two weeks of LT, there was a considerable accumulation of sucrose in leaves, which subsequently decreased as the inflorescences developed. During the LT period, the expression of sucrose-phosphate synthase (SPS) significantly increased, whereas that of some members of the SWEET family, sugar transporters, was suppressed before inflorescence initiation. As the inflorescence initiated and elongated, the expression of SWEET family members increased again. These results indicated that exposure to low temperatures triggered sink transition and sugar accumulation in leaves, which were then translocated and utilized for inflorescence development. This finding implies a significant association between leaf sugars and floral induction, highlighting their pivotal roles in the flowering process of Phalaenopsis.

中文翻译：

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蝴蝶兰低温暴露下水沉过渡过程中叶糖含量的变化


蝴蝶兰需要长时间的低温才能开花，这与叶片中的可溶性糖含量高度相关。本研究旨在探讨蝴蝶兰汇过渡过程中叶糖含量的变化。蝴蝶兰皇后啤酒 'Mantefon' 克隆在 28 °C 下生长，然后暴露于 20 °C 进行花诱导。在低温 （LT） 处理 0 、 2 、 6 和 10 周后对叶片进行取样，以分析可溶性糖含量和 RNA-seq。将用稳定碳同位素标记的外源蔗糖施用于成熟叶片。花序在两周后还没有出现，但在 6 周和 10 周后分别长 0.5-1 厘米和 5-10 厘米。碳同位素分析显示，在花诱导过程中，叶糖从叶转移到花序，而不是新发育的叶子等营养器官。LT 两周后，蔗糖在叶片中有相当大的积累，随后随着花序的发育而减少。在 LT 期间，蔗糖-磷酸合酶 （SPS） 的表达显著增加，而 SWEET 家族的一些成员糖转运蛋白的表达在花序开始前受到抑制。随着花序的开始和拉长，SWEET 家族成员的表达量再次增加。这些结果表明，暴露于低温下会触发叶片中的汇过渡和糖积累，然后被易位并用于花序发育。这一发现意味着叶糖与花诱导之间存在显着关联，突出了它们在蝴蝶兰开花过程中的关键作用。