Melatonin is a signaling molecule that is involved in inducing plantsʼ abiotic stress tolerance. To determine the possible effects of the melatonin pre-treatment on thermotolerance in strawberry (Fragaria × ananassa Duch.), the heat-sensitive cultivar Ventana was subjected to high temperatures (35 °C and 40 °C) for 10 h after pre-treatment with 0, 50, and 100 μM melatonin. High temperature increased malondialdehyde and H₂O₂ contents and reduced relative water content, carotenoid content, and catalase and ascorbate peroxidase activities, which led to a marked reduction in chlorophyll fluorescence. However, pre-treatment with melatonin at 100 μM decreased heat injury symptoms and induced antioxidant mechanisms in heat-sensitive cultivar Ventana, increasing heat tolerance. The results showed that when the melatonin pre-treated strawberry plants were exposed to high temperature (40 °C) for 2 h, the levels of FaTHsfA2a and HSP90 mRNA significantly increased, but after heat treating at 40 °C for 5 and 10 h, their mRNA levels were as similar as the control. The results support the hypothesis that melatonin acts as an important signaling molecule during heat stress to induce protective mechanisms via up-regulating the expression of defense HSF (FaTHsfA2a, FaTHSFB1a) and HSP (HSP90) genes.

褪黑素是一种信号分子，参与诱导植物的非生物胁迫耐受性。为了确定褪黑素预处理对草莓（Fragaria  ×  ananassa Duch。）耐热性的可能影响，将热敏感品种Ventana预处理后置于高温（35°C和40°C）下10 h含0、50和100μM褪黑素。高温升高的丙二醛和H ₂ O ₂含量和相对水含量，类胡萝卜素含量以及过氧化氢酶和抗坏血酸过氧化物酶活性的降低，导致叶绿素荧光显着降低。但是，以100μM褪黑素预处理可减少热敏感品种Ventana的热损伤症状并诱导抗氧化机制，从而提高耐热性。结果表明，将褪黑素预处理的草莓植株置于高温（40°C）下2 h，FaTHsfA2a和HSP90的水平mRNA显着增加，但在40°C热处理5和10 h后，其mRNA水平与对照组相似。该结果支持以下假设：褪黑激素是热应激期间通过上调防御性HSF（FaTHsfA2a，FaTHSFB1a）和HSP（HSP90）基因表达来诱导保护机制的重要信号分子。