Lautenbach Julia, Abbas Qussai, Brajkovic Sarah, Sieberer Tobias, Neumüller Michael, Kuster Bernhard, Poppenberger Brigitte
Biotechnology of Horticultural Crops, TUM School of Life Sciences, Technical University of Munich, Liesel-Beckmann-Str. 1, Freising, Germany.
Chair of Bioinformatics, TUM School of Life Sciences, Technical University of Munich, Am Staudengarten 2, Freising, Germany.
J Proteomics. 2025 Aug 15;319:105470. doi: 10.1016/j.jprot.2025.105470. Epub 2025 Jun 3.
Anthocyanins are colorful plant pigments with antioxidant properties, and a diet rich in these flavonoids bears health benefits. Therefore, a strong anthocyanin accumulation in edible plant parts is of significant interest, and in Malus domestica, the domesticated apple, certain red-fleshed apple varieties exhibit this trait. Enhanced anthocyanin accumulation in the flesh of apple fruits is attributed to the hyperactivation of the MYB transcription factor MdMYB10, which acts as a key regulator of anthocyanin biosynthesis by inducing the expression of multiple biosynthetic genes. While several studies have explored the underlying genetic mutations and resulting transcriptome changes, there is a lack of research on proteome alterations that cause the red-fleshed apple phenotype. To address this gap, a mass spectrometry-based proteomics approach was employed. Comparative proteomics identified differentially abundant proteins in young and mature fruits of the red-fleshed 'Bay13645' variety compared to the white-fleshed 'Gala'. Whereas several MYB transcription factors were enriched during early fruit development, they were no longer among the hyper-abundant proteins in ripe fruits of the red-fleshed genotype. In contrast, anthocyanin biosynthetic enzymes were enriched more strongly in ripe fruits of the red-fleshed cultivar, supporting previous results which had indicated developmental stage-specific differences in the control of the pigmentation process. The proteomic approach also identified novel regulatory factors and enzymes that may contribute to the red-fleshed apple phenotype, including a BAHD acyltransferase, Mal d proteins, and transcription factors of diverse families, and their potential relevance for the exhibition of this trait is discussed. SIGNIFICANCE: This study offers insights into the molecular mechanisms driving anthocyanin accumulation in red-fleshed apples. Utilizing a mass spectrometry-based proteomics strategy, the study reveals proteome alterations during fruit development that underlie the red-fleshed phenotype in Malus domestica. Notably, key enzymes of anthocyanin biosynthesis were markedly upregulated, underscoring their role in the pigmentation of the apple fruit pulp. Importantly, the study also identifies previously uncharacterized proteins, including a BAHD acyltransferase and a suite of transcription factors, shedding new light on the regulatory network orchestrating anthocyanin accumulation. These findings significantly expand our understanding of metabolic pathways that contribute to fruit pigmentation and open promising avenues for targeted crop improvement.
花青素是具有抗氧化特性的彩色植物色素，富含这些类黄酮的饮食对健康有益。因此，可食用植物部位中强烈的花青素积累备受关注，在驯化苹果品种——苹果（Malus domestica）中，某些红肉苹果品种就表现出这一特性。苹果果实果肉中花青素积累的增强归因于MYB转录因子MdMYB10的过度激活，该转录因子通过诱导多个生物合成基因的表达，作为花青素生物合成的关键调节因子。虽然有几项研究探讨了潜在的基因突变和由此导致的转录组变化，但对于导致红肉苹果表型的蛋白质组改变缺乏研究。为了填补这一空白，采用了基于质谱的蛋白质组学方法。比较蛋白质组学确定了红肉‘Bay13645’品种与白肉‘Gala’品种的幼果和成熟果实中差异丰富的蛋白质。虽然在果实发育早期有几种MYB转录因子富集，但在红肉基因型的成熟果实中，它们不再是高丰度蛋白质。相反，花青素生物合成酶在红肉品种的成熟果实中富集得更强，这支持了先前表明色素沉着过程控制存在发育阶段特异性差异的结果。蛋白质组学方法还鉴定出可能导致红肉苹果表型的新调节因子和酶，包括一种BAHD酰基转移酶、苹果过敏原蛋白（Mal d蛋白）和不同家族的转录因子，并讨论了它们与这一性状表现的潜在相关性。意义：本研究深入了解了驱动红肉苹果中花青素积累的分子机制。该研究利用基于质谱的蛋白质组学策略，揭示了苹果果实发育过程中构成红肉表型基础的蛋白质组变化。值得注意的是，花青素生物合成的关键酶明显上调，突出了它们在苹果果肉色素沉着中的作用。重要的是，该研究还鉴定出了以前未表征的蛋白质，包括一种BAHD酰基转移酶和一组转录因子，为协调花青素积累的调控网络提供了新的线索。这些发现显著扩展了我们对导致果实色素沉着的代谢途径的理解，并为有针对性的作物改良开辟了有前景的途径。
