果皮脱绿是许多柑橘类水果中果实成熟的最明显方面,因为它对适销性很重要。在这项研究中,在萨摩普通话(CitrusunshiuMarc。)水果。丙烯处理引发快速脱绿(4-6天内),柑橘颜色指数(CCI)和叶绿素损失的增加表明。在28-42天后,在10°C和15°C的水果中也观察到果皮脱绿,随着CCI逐渐增加和叶绿素减少。然而,水果在5°C,20°C,25°C保持绿色,在42天的储存期间,未记录到果皮CCI和叶绿素含量的实质性变化。然后通过RNA-Seq分析用丙烯处理4天和在不同温度下储存28天的果皮的转录组。我们确定了三类由(i)丙烯调节的差异表达基因(类比,乙烯)单独,(ii)低温(5°C,10°C,或15°C与25°C)单独,和(iii)丙烯或低温。与叶绿素降解相关的基因编码蛋白(如CuSGR1、CuNOL、CuACD2,CuCAB2和CuLHCB2)和转录因子(CuERF114)在丙烯或低温下差异表达。为了进一步检查温度诱导的途径,我们还监测了树上果实成熟过程中的基因表达与采后.树上果皮退绿的开始与田间温度的秋季下降相吻合,并伴随着低温调控基因的差异表达。相反,仅由丙烯调节的基因(例如CuCOPT1和CuPOX-A2)在树上的果皮脱绿过程中表现出微不足道的表达变化。这些发现表明,低温可能参与与果实成熟相关的果皮脱绿,而与乙烯无关。
Peel
degreening is the most conspicuous aspect of fruit ripening in many citrus fruits because of its importance for marketability. In this study, peel
degreening in response to propylene (an ethylene analog) and at varying storage temperatures was characterized in Satsuma mandarin (Citrus unshiu Marc.) fruit. Propylene treatment triggered rapid peel
degreening (within 4-6 days), indicated by an increase in the citrus color index (CCI) and chlorophyll loss. Peel
degreening was also observed in fruit at 10°C and 15°C after 28-42 days, with gradual CCI increase and chlorophyll reduction. However, fruit at 5°C, 20°C, and 25°C remained green, and no substantial changes in peel CCI and chlorophyll content were recorded during the 42-day storage duration. The transcriptomes of peels of fruit treated with propylene for 4 days and those stored at varying temperatures for 28 days were then analyzed by RNA-Seq. We identified three categories of differentially expressed genes that were regulated by (i) propylene (and by analogy, ethylene) alone, (ii) low temperature (5°C, 10°C, or 15°C vs. 25°C) alone, and (iii) either propylene or low temperature. Gene-encoding proteins associated with chlorophyll degradation (such as CuSGR1, CuNOL, CuACD2, CuCAB2, and CuLHCB2) and a transcription factor (CuERF114) were differentially expressed by propylene or low temperature. To further examine temperature-induced pathways, we also monitored gene expression during on-tree fruit maturation vs. postharvest. The onset of on-tree peel
degreening coincided with autumnal drops in field temperatures, and it was accompanied by differential expression of low temperature-regulated genes. On the contrary, genes that were exclusively regulated by propylene (such as CuCOPT1 and CuPOX-A2) displayed insignificant expression changes during on-tree peel degreening. These findings indicate that low temperatures could be involved in the fruit ripening-related peel degreening independently of ethylene.