Mercado-Hornos José A, Rodríguez-Hiraldo Claudia, Guerrero Consuelo, Posé Sara, Matas Antonio J, Rubio Lourdes, Mercado José A
Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora" (IHSM-UMA-CSIC), Universidad de Málaga, 29071 Málaga, Spain.
Departamento de Botánica y Fisiología Vegetal, Universidad de Málaga, 29071 Málaga, Spain.
Plants (Basel). 2025 Jul 20;14(14):2241. doi: 10.3390/plants14142241.
Potassium is the most abundant macronutrient in plants, participating in essential physiological processes such as turgor maintenance. A reduction in cell turgor is a hallmark of the ripening process associated with fruit softening. The dynamic of K fluxes in fleshy fruits is largely unknown; however, the reallocation of K into the apoplast has been proposed as a contributing factor to the decrease in fruit turgor, contributing to fruit softening. High-affinity K transporters belonging to the KUP/HT/HAK transporter family have been implicated in this process in some fruits. In this study, a comprehensive genome-wide analysis of the KUP/KT/HAK family of high-affinity K transporters in strawberry ( × Duch.) was conducted, identifying 60 putative transporter genes. The chromosomal distribution of the FaKUP gene family and phylogenetic relationship and structure of predicted proteins were thoroughly examined. Transcriptomic profiling revealed the expression of 19 FaKUP genes within the fruit receptacle, with a predominant downregulation observed during ripening, particularly in , and . This pattern suggests their functional relevance in early fruit development and turgor maintenance. Mineral composition analyses confirmed that K is the most abundant macronutrient in strawberry fruits, exhibiting a slight decrease as ripening progressed. Membrane potential (E) and diffusion potentials (E) at increasing external K concentrations were measured by electrophysiology in parenchymal cells of green and white fruits. The results obtained suggest a significant diminution in cytosolic K levels in white compared to green fruits. Furthermore, the slope of change in E at increasing external K concentration indicated a lower K permeability of the plasma membrane in white fruits, aligning with transcriptomic data. This study provides critical insights into the regulatory mechanisms of K transport during strawberry ripening and identifies potential targets for genetic modifications aimed at enhancing fruit firmness and shelf life.
钾是植物中含量最丰富的大量营养素，参与诸如维持膨压等重要生理过程。细胞膨压降低是与果实软化相关的成熟过程的一个标志。肉质果实中钾离子通量的动态变化在很大程度上尚不清楚；然而，钾向质外体的重新分配已被认为是导致果实膨压降低的一个因素，进而促成果实软化。属于KUP/HT/HAK转运蛋白家族的高亲和力钾转运蛋白在一些果实的这一过程中发挥了作用。在本研究中，对草莓（× 杜氏）中高亲和力钾转运蛋白的KUP/KT/HAK家族进行了全面的全基因组分析，鉴定出60个推定的转运蛋白基因。深入研究了FaKUP基因家族的染色体分布以及预测蛋白质的系统发育关系和结构。转录组分析揭示了果实托杯中有19个FaKUP基因表达，在成熟过程中观察到主要是下调，特别是在 、 和 中。这种模式表明它们在果实早期发育和膨压维持中具有功能相关性。矿物质成分分析证实，钾是草莓果实中含量最丰富的大量营养素，随着成熟进程略有下降。通过电生理学方法测量了绿色和白色果实实质细胞在外部钾浓度增加时的膜电位（E）和扩散电位（E）。获得的结果表明，与绿色果实相比，白色果实的胞质钾水平显著降低。此外，在外部钾浓度增加时E的变化斜率表明白色果实中质膜的钾通透性较低，这与转录组数据一致。本研究为草莓成熟过程中钾转运的调控机制提供了关键见解，并确定了旨在提高果实硬度和货架期的基因修饰潜在靶点。
