Massot Capucine, Bancel Doriane, Lopez Lauri Félicie, Truffault Vincent, Baldet Pierre, Stevens Rebecca, Gautier Hélène
INRA, UR 1115 Plantes et Système de cultures Horticoles, Avignon, France.
EA4279, Université d'Avignon, Avignon, France.
PLoS One. 2013 Dec 19;8(12):e84474. doi: 10.1371/journal.pone.0084474. eCollection 2013.
Understanding how the fruit microclimate affects ascorbate (AsA) biosynthesis, oxidation and recycling is a great challenge in improving fruit nutritional quality. For this purpose, tomatoes at breaker stage were harvested and placed in controlled environment conditions at different temperatures (12, 17, 23, 27 and 31 °C) and irradiance regimes (darkness or 150 µmol m(-2) s(-1)). Fruit pericarp tissue was used to assay ascorbate, glutathione, enzymes related to oxidative stress and the AsA/glutathione cycle and follow the expression of genes coding for 5 enzymes of the AsA biosynthesis pathway (GME, VTC2, GPP, L-GalDH, GLDH). The AsA pool size in pericarp tissue was significantly higher under light at temperatures below 27 °C. In addition, light promoted glutathione accumulation at low and high temperatures. At 12 °C, increased AsA content was correlated with the enhanced expression of all genes of the biosynthesis pathway studied, combined with higher DHAR and MDHAR activities and increased enzymatic activities related to oxidative stress (CAT and APX). In contrast, at 31 °C, MDHAR and GR activities were significantly reduced under light indicating that enzymes of the AsA/glutathione cycle may limit AsA recycling and pool size in fruit pericarp, despite enhanced expression of genes coding for AsA biosynthesis enzymes. In conclusion, this study confirms the important role of fruit microclimate in the regulation of fruit pericarp AsA content, as under oxidative conditions (12 °C, light) total fruit pericarp AsA content increased up to 71%. Moreover, it reveals that light and temperature interact to regulate both AsA biosynthesis gene expression in tomato fruits and AsA oxidation and recycling.
了解果实微气候如何影响抗坏血酸（AsA）的生物合成、氧化和循环利用是提高果实营养品质的一大挑战。为此，采收了转色期的番茄，并将其置于不同温度（12、17、23、27和31°C）和光照条件（黑暗或150 μmol m⁻² s⁻¹）的可控环境中。利用果实果皮组织检测抗坏血酸、谷胱甘肽、与氧化应激相关的酶以及AsA/谷胱甘肽循环，并追踪AsA生物合成途径中5种酶（GME、VTC2、GPP、L-GalDH、GLDH）编码基因的表达情况。在低于27°C的温度下，光照条件下果皮组织中的AsA库大小显著更高。此外，光照在低温和高温下均促进了谷胱甘肽的积累。在12°C时，AsA含量的增加与所研究的生物合成途径所有基因的表达增强相关，同时伴随着更高的DHAR和MDHAR活性以及与氧化应激相关的酶活性增加（CAT和APX）。相反，在31°C时，光照下MDHAR和GR活性显著降低，这表明尽管AsA生物合成酶编码基因的表达增强，但AsA/谷胱甘肽循环的酶可能会限制果实果皮中AsA的循环利用和库大小。总之，本研究证实了果实微气候在调节果实果皮AsA含量方面的重要作用，因为在氧化条件下（12°C，光照），果实果皮中的总AsA含量增加了71%。此外，研究还揭示了光照和温度相互作用，共同调节番茄果实中AsA生物合成基因的表达以及AsA的氧化和循环利用。
