Cordenunsi-Lysenko Beatriz Rosana, Nascimento João Roberto Oliveira, Castro-Alves Victor Costa, Purgatto Eduardo, Fabi João Paulo, Peroni-Okyta Fernanda Helena Gonçalves
Department of Food Science and Experimental Nutrition, School of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil.
Food Research Center (FoRC), Research, Innovation and Dissemination Centers, São Paulo Research Foundation (CEPID-FAPESP), São Paulo, Brazil.
Front Plant Sci. 2019 Apr 2;10:391. doi: 10.3389/fpls.2019.00391. eCollection 2019.
The monocot banana fruit is one of the most important crops worldwide. As a typical climacteric fruit, the harvest of commercial bananas usually occurs when the fruit is physiologically mature but unripe. The universal treatment of green bananas with ethylene or ethylene-releasing compounds in order to accelerate and standardize the ripening of a bunch of bananas mimics natural maturation after increasing the exogenous production of ethylene. The trigger of autocatalytic ethylene production regulated by a dual positive feedback loop circuit derived from a NAC gene and three MADS genes results in metabolic processes that induce changes in the primary metabolism of bananas. These changes include pulp softening and sweetening which are sensorial attributes that determine banana postharvest quality. During fruit development, bananas accumulate large amounts of starch (between 15 and 35% w/w of their fresh weight, depending on the cultivar). Pulp softening and sweetening during banana ripening are attributed not only to changes in the activities of cell wall hydrolases but also to starch-to-sugar metabolism. Therefore, starch granule erosion and disassembling are key events that lead bananas to reach their optimal postharvest quality. The knowledge of the mechanisms that regulate sugar primary metabolism during banana ripening is fundamental to reduce postharvest losses and improve final product quality, though. Recent studies have shown that ethylene-mediated regulation of starch-degrading enzymes at transcriptional and translational levels is crucial for sugar metabolism in banana ripening. Furthermore, the crosstalk between ethylene and other hormones including indole-3-acetic acid and abscisic acid also influences primary sugar metabolism. In this review, we will describe the state-of-the-art sugar primary metabolism in bananas and discuss the recent findings that shed light on the understanding of the molecular mechanisms involved in the regulation of this metabolism during fruit ripening.
单子叶香蕉果实是全球最重要的作物之一。作为典型的跃变型果实，商业香蕉通常在生理成熟但未成熟时收获。为了加速并使一串香蕉的成熟标准化，普遍采用乙烯或乙烯释放化合物处理青香蕉，这在增加乙烯外源生成后模拟了自然成熟过程。由一个NAC基因和三个MADS基因衍生的双重正反馈回路调节的自催化乙烯生成触发了代谢过程，这些过程诱导香蕉初级代谢发生变化。这些变化包括果肉软化和变甜，它们是决定香蕉采后品质的感官特性。在果实发育过程中，香蕉积累了大量淀粉（根据品种不同，占鲜重的15%至35%，重量/重量）。香蕉成熟期间的果肉软化和变甜不仅归因于细胞壁水解酶活性的变化，还归因于淀粉到糖的代谢。因此，淀粉颗粒的侵蚀和分解是使香蕉达到最佳采后品质的关键事件。然而，了解香蕉成熟过程中调节糖初级代谢的机制对于减少采后损失和提高最终产品质量至关重要。最近的研究表明，乙烯在转录和翻译水平上对淀粉降解酶的调节对于香蕉成熟过程中的糖代谢至关重要。此外，乙烯与包括吲哚-3-乙酸和脱落酸在内的其他激素之间的相互作用也影响初级糖代谢。在这篇综述中，我们将描述香蕉糖初级代谢的最新进展，并讨论最近的研究结果，这些结果有助于深入了解果实成熟过程中这种代谢调节所涉及的分子机制。
