Mitalo Oscar W, Kang Seung Wong, Tran Long T, Kubo Yasutaka, Ariizumi Tohru, Ezura Hiroshi
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
Tsukuba-Plant Innovation Research Center, University of Tsukuba, Tsukuba, Japan.
Front Plant Sci. 2023 Jul 28;14:1227349. doi: 10.3389/fpls.2023.1227349. eCollection 2023.
Cold storage is widely used to extend the postharvest life of most horticultural crops, including tomatoes, but this practice triggers cold stress and leads to the development of undesirable chilling injury (CI) symptoms. The underlying mechanisms of cold stress response and CI development in fruits remain unclear as they are often intermingled with fruit ripening changes. To gain insight into cold responses in fruits, we examined the effect of the potent ethylene signaling inhibitor 1-methylcyclopropene (1-MCP) on fruit ripening, CI occurrence and gene expression in mature green tomatoes during storage at 20°C and 5°C. 1-MCP treatments effectively inhibited ethylene production and peel color changes during storage at 20°C. Storage at 5°C also inhibited both ethylene production and peel color change; during rewarming at 20°C, 1-MCP treatments inhibited peel color change but failed to inhibit ethylene production. Furthermore, fruits stored at 5°C for 14 d developed CI symptoms (surface pitting and decay) during the rewarming period at 20°C regardless of 1-MCP treatment. Subsequent RNA-Seq analysis revealed that cold stress triggers a large-scale transcriptomic adjustment, as noticeably more genes were differentially expressed at 5°C (8,406) than at 20°C (4,814). More importantly, we have found some important divergences among genes involved in fruit ripening (up- or down-regulated at 20°C; inhibited by 1-MCP treatment) and those involved in cold stress (up- or down-regulated at 5°C; unaffected by 1-MCP treatment). Transcriptomic adjustments unique to cold stress response were associated with ribosome biogenesis, NcRNA metabolism, DNA methylation, chromatin formation/remodeling, and alternative splicing events. These data should foster further research into cold stress response mechanisms in fruits with the ultimate aim of improving tolerance to low temperature and reduction of CI symptoms during cold storage.
冷藏被广泛用于延长包括番茄在内的大多数园艺作物的采后寿命，但这种做法会引发冷胁迫，并导致出现不良的冷害（CI）症状。果实中冷胁迫响应和冷害发生的潜在机制仍不清楚，因为它们常常与果实成熟变化交织在一起。为了深入了解果实的冷响应，我们研究了强效乙烯信号抑制剂1-甲基环丙烯（1-MCP）对成熟绿番茄在20°C和5°C贮藏期间果实成熟、冷害发生及基因表达的影响。1-MCP处理有效地抑制了20°C贮藏期间的乙烯生成和果皮颜色变化。5°C贮藏也抑制了乙烯生成和果皮颜色变化；在20°C回温期间，1-MCP处理抑制了果皮颜色变化，但未能抑制乙烯生成。此外，无论是否进行1-MCP处理，在5°C贮藏14天的果实在20°C回温期间都会出现冷害症状（表面凹陷和腐烂）。随后的RNA测序分析表明，冷胁迫引发了大规模的转录组调整，因为在5°C时差异表达的基因（8406个）明显多于在20°C时（4814个）。更重要的是，我们发现参与果实成熟的基因（在20°C时上调或下调；受1-MCP处理抑制）与参与冷胁迫的基因（在5°C时上调或下调；不受1-MCP处理影响）之间存在一些重要差异。冷胁迫响应特有的转录组调整与核糖体生物合成、非编码RNA代谢、DNA甲基化、染色质形成/重塑以及可变剪接事件有关。这些数据应促进对果实冷胁迫响应机制的进一步研究，最终目的是提高对低温的耐受性并减少冷藏期间的冷害症状。
