马惠玲等《POSTHARVEST BIOLOGY AND TECHNOLOGY》2024年
论文题目：Controlled atmosphere storage alleviates the browning of walnut ( Juglans regia L.) fruit through enhancing GABA-mediated energy metabolism
论文作者：Niu Ye, Dongli Zhang, Shan Liu, Yongqi Zhang, Yifan Wang, Yan Tang （唐燕） , Xiangna Yang（杨向娜） , Jiahao Chai, Yanping Ma* , Huiling Ma*
论文摘要：Browning is the primary physiological damage that shortens the postharvest life and deteriorates the quality of stored fruits. Controlled atmosphere (CA) storage has been shown to be effective in alleviating the browning of ‘Xifu 1’ in-hull walnut; however, its alleviation mechanism is less understood. To further explore the effect and regulatory mechanism of CA on the browning of fresh in-hull walnut, we stored four varieties of in-hull walnuts under CA-treated (5% O2 + 7.5% CO2) and untreated conditions at 0 ± 0.5 °C with 70–80% relative humidity for 70 d. The indicators related to browning and γ-aminobutyric acid (GABA) metabolism were measured until 56 d of storage. The results showed that the CA significantly increased GABA levels by maintaining higher activities of glutamate decarboxylase (GAD), GABA transaminase (GABAT) and succinate dehydrogenase (SDH). This reduced the changes in the browning index (BI), color values, and respiration rate (RR) of the four walnut fruit varieties compared with controls during storage. Consistent with the active GABA metabolism, higher energy charge (EC) and adenosine triphosphate (ATP), succinic acid (SA), malic acid (MLA), fumaric acid (FA), and citric acid (CTA) contents were also observed in the CA-treated walnut hull compared to the controls. The epicarp degradation of the CA-treated ‘Xifu 1′ walnut fruit occurred later, and their mitochondria and cells maintained better integrity compared to the controls. Among the differentially expressed genes (DEGs) screened via RNA-Sequencing (RNA-Seq), 32 were annotated as part of the citrate cycle (TCA cycle) pathway, and 27 were annotated in the GABA metabolism pathway. Real-time quantitative PCR (RT-qPCR) analysis showed that eight candidate genes were closely related to the effect of CA on the synthesis, transport, and transformation of GABA. In conclusion, CA effectively controlled the browning of different varieties of fresh in-hull walnuts by enhancing GABA metabolism and maintaining energy balance.
褐变是影响果实采后寿命和贮藏品质的主要生理伤害。前期试验发现气调（CA）贮藏对减轻‘西扶1’青皮核桃褐变有显著作用，然而，其作用机制却知之甚少，限制了CA的应用范围。我们将4个品种的青皮核桃在CA处理（5%O2+7.5%CO2）和未处理（对照）的条件下，在0±0.5°C、70–80%相对湿度下贮藏70 d。测定褐变和γ-氨基丁酸（GABA）代谢的相关指标。结果表明，CA通过维持较高的谷氨酸脱羧酶（GAD）、GABA转氨酶（GABAT）和琥珀酸脱氢酶（SDH）活性，显著提高GABA水平。CA降低了4个核桃果实品种在贮藏过程中褐变指数（BI）、色差值和呼吸速率（RR）的变化。与活跃的GABA代谢一致，CA较对照果保持了较高的三磷酸腺苷（ATP）和能荷值（EC）、琥珀酸（SA）、苹果酸（MLA）、富马酸（FA）和柠檬酸（CTA）含量。CA处理的‘西扶1’核桃果实的外果皮降解发生较晚，线粒体和细胞保持了更好的完整性。通过转录组测序（RNA-Seq）筛选的差异表达基因（DEGs）中，32个为三羧酸循环（TCA）相关基因，27个为GABA代谢途径相关基因。实时定量PCR（RT-qPCR）分析表明，8个候选基因与CA对GABA合成、转运和转化的影响密切相关。因此，CA通过增强GABA代谢和维持能量平衡，有效地控制了不同品种青皮核桃的褐变。论文为进一步研究CA控制果实褐变的分子机制奠定了基础，对促进CA在易褐变果实保鲜的广范应用具有重要意义。