Zhang Ming Ke, Zhang Mei Ping, Mazourek Michael, Tadmor Yaakov, Li Li
College of Horticulture, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
Planta. 2014 Nov;240(5):1063-74. doi: 10.1007/s00425-014-2147-6. Epub 2014 Aug 20.
Storage promotes carotenoid accumulation and converts amylochromoplasts into chromoplasts in winter squash. Such carotenoid enhancement is likely due to continuous biosynthesis along with reduced turnover and/or enhanced sequestration. Postharvest storage of fruits and vegetables is often required and frequently results in nutritional quality change. In this study, we investigated carotenoid storage plastids, carotenoid content, and its regulation during 3-month storage of winter squash butternut fruits. We showed that storage improved visual appearance of fruit flesh color from light to dark orange, and promoted continuous accumulation of carotenoids during the first 2-month storage. Such an increased carotenoid accumulation was found to be concomitant with starch breakdown, resulting in the conversion of amylochromoplasts into chromoplasts. The butternut fruits contained predominantly β-carotene, lutein, and violaxanthin. Increased ratios of β-carotene and violaxanthin to total carotenoids were noticed during the storage. Analysis of carotenoid metabolic gene expression and PSY protein level revealed a decreased expression of carotenogenic genes and PSY protein following the storage, indicating that the increased carotenoid level might not be due to increased biosynthesis. Instead, the increase likely resulted from a continuous biosynthesis with a possibly reduced turnover and/or enhanced sequestration, suggesting a complex regulation of carotenoid accumulation during fruit storage. This study provides important information to our understanding of carotenogenesis and its regulation during postharvest storage of fruits.
贮藏可促进南瓜中类胡萝卜素的积累，并使淀粉质体在冬季转化为有色体。这种类胡萝卜素的增加可能是由于持续的生物合成以及周转率降低和/或隔离增强。水果和蔬菜的采后贮藏通常是必要的，并且经常会导致营养品质的变化。在本研究中，我们调查了南瓜果实3个月贮藏期间类胡萝卜素贮藏质体、类胡萝卜素含量及其调控。我们发现，贮藏改善了果肉颜色的视觉外观，从浅橙色变为深橙色，并在贮藏的前两个月促进了类胡萝卜素的持续积累。发现这种类胡萝卜素积累的增加与淀粉分解同时发生，导致淀粉质体转化为有色体。南瓜果实主要含有β-胡萝卜素、叶黄素和紫黄质。贮藏期间，β-胡萝卜素和紫黄质与总类胡萝卜素的比例增加。对类胡萝卜素代谢基因表达和PSY蛋白水平的分析表明，贮藏后类胡萝卜素生成基因和PSY蛋白的表达降低，这表明类胡萝卜素水平的增加可能不是由于生物合成增加。相反，这种增加可能是由于持续的生物合成，周转率可能降低和/或隔离增强，这表明果实贮藏期间类胡萝卜素积累的调控较为复杂。本研究为我们理解果实采后贮藏期间类胡萝卜素的生成及其调控提供了重要信息。
