Khan Muhammad Abbas, Zaman Fatima, Liu Yong-Zhong, Alam Shariq Mahmood, Liu Dong-Hai, Han Han, Luo Yin
National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, People's Republic of China.
Physiol Plant. 2025 May-Jun;177(3):e70303. doi: 10.1111/ppl.70303.
Fleshy fruit taste and quality are influenced by their soluble sugar contents. In order to improve the fruit quality, it is imperative to better understand how soluble sugars accumulate in fruit vacuoles. A previous report showed that the type I H-pyrophosphatase regulates the vacuolar storage of sucrose in citrus fruits, but its transcriptional regulation still remains elusive. In this study, the NAC transcription factor gene CsNAC47 was functionally characterized and found to localize predominantly within the nucleus, consistent with its predicted role in transcriptional regulation. Moreover, drought stress markedly upregulated the transcript levels of CsNAC47 and CsVPP1/2 in Nanfeng tangerine (Citrus reticulata) fruits, indicating their potential role in sugars accumulation. Transient overexpression of CsNAC47 and CsVPP1/2 led to enhanced accumulation of soluble sugars in citrus fruit juice sacs, while virus-induced gene silencing (VIGS) of CsNAC47 and CsVPP1/2 inhibited sugar accumulation. Stable transformation in Micro-Tom tomato indicated that overexpression of CsNAC47 and CsVPP1/2 significantly elevated the vacuolar storage of soluble sugar contents. We found out through yeast one-hybrid screening assay and dual luciferase assays that CsNAC47 directly binds to the promoters of CsVPP1/2 and regulates their gene expression. This study offers novel insights into the transcriptional regulation of soluble sugar accumulation in citrus fruits under drought stress, specifically through the interaction between CsNAC47 and CsVPP1/2, which will ultimately contribute to improving fruit quality in the future.
肉质果实的口感和品质受其可溶性糖含量的影响。为了提高果实品质，必须更好地了解可溶性糖如何在果实液泡中积累。先前的一份报告表明，I型H⁃焦磷酸酶调节柑橘类果实中蔗糖的液泡储存，但其转录调控仍不清楚。在本研究中，对NAC转录因子基因CsNAC47进行了功能鉴定，发现其主要定位于细胞核内，与其在转录调控中的预测作用一致。此外，干旱胁迫显著上调了南丰蜜橘（Citrus reticulata）果实中CsNAC47和CsVPP1/2的转录水平，表明它们在糖分积累中具有潜在作用。CsNAC47和CsVPP1/2的瞬时过表达导致柑橘果实汁囊中可溶性糖的积累增加，而CsNAC47和CsVPP1/2的病毒诱导基因沉默（VIGS）抑制了糖分积累。在Micro-Tom番茄中的稳定转化表明，CsNAC47和CsVPP1/2的过表达显著提高了可溶性糖含量的液泡储存。我们通过酵母单杂交筛选试验和双荧光素酶试验发现，CsNAC47直接与CsVPP1/2的启动子结合并调节其基因表达。本研究为干旱胁迫下柑橘果实可溶性糖积累的转录调控提供了新的见解，特别是通过CsNAC47和CsVPP1/2之间的相互作用，这最终将有助于未来改善果实品质。
