The plant growth regulator N-(2‑chloro-4-pyridyl)-N′-phenylurea (CPPU) is applied to induce parthenocarpic fruit setting in melon (Cucumis melo L.) production. However, CPPU-induced fruits frequently exhibit a decline in quality attributes, such as sucrose, aroma, and pigmentation, the mechanisms underlying these changes remain largely unclear. This research assessed the effects of CPPU application on carotenoid biosynthesis in the pulp during melon fruit development, aiming to elucidate the underlying mechanisms. Transcriptome and metabolome analyses were employed to examine changes in pigment and hormone levels in melon fruit at various developmental stages following CPPU treatment. The results indicated that CPPU application for fruit setting significantly reduced β-carotene content in the fruit pulp compared to fruits resulting from artificial pollination. Transcriptome analysis revealed a decrease in the expression of carotenoid biosynthesis genes (e.g., PSY1/2, Z-ISO, and LYCB), while the expression of catabolic enzyme genes (e.g., NCED5/6, NXS, and CCD4) were up-regulated following CPPU application. Metabolome analysis showed a decrease in gibberellin production during the development of CPPU-induced fruits compared to pollinated samples. Furthermore, exogenous gibberellin application recovered the pigment defects in the CPPU-induced parthenocarpic fruits. This study provides novel insights into how CPPU-induced parthenocarpy affects melon pulp pigmentation during development, offering valuable theoretical foundations for improving fruit set management in melon cultivation.

中文翻译：

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CPPU 诱导的单性结实甜瓜果实中赤霉素依赖性果肉色素沉着：来自代谢组和转录组分析的见解


植物生长调节剂 N-（2-氯-4-吡啶基）-N′-苯脲 （CPPU） 用于诱导甜瓜 （Cucumis melo L.） 生产中的单性结实坐果。然而，CPPU 诱导的水果经常表现出质量属性的下降，例如蔗糖、香气和色素沉着，这些变化背后的机制在很大程度上仍不清楚。本研究评估了 CPPU 施用对甜瓜果实发育过程中果肉中类胡萝卜素生物合成的影响，旨在阐明其潜在机制。采用转录组和代谢组分析来检查 CPPU 处理后瓜果不同发育阶段色素和激素水平的变化。结果表明，与人工授粉的果实相比，CPPU 用于坐果的施用显著降低了果肉中 β-胡萝卜素的含量。转录组分析显示类胡萝卜素生物合成基因 （例如 PSY1/2 、 Z-ISO 和 LYCB） 的表达降低，而分解代谢酶基因 （例如 NCED5/6 、 NXS 和 CCD4） 的表达在 CPPU 应用后上调。代谢组分析显示，与授粉样品相比，CPPU 诱导的果实发育过程中赤霉素的产生减少。此外，外源赤霉素应用恢复了 CPPU 诱导的孤雌果中的色素缺陷。本研究为 CPPU 诱导的孤雌果皮如何影响甜瓜发育过程中的果肉色素沉着提供了新的见解，为改善甜瓜种植中的坐果管理提供了宝贵的理论基础。