Department of Pomology, Faculty of Agriculture, Assiut University, Assiut, 71526, Egypt.
Maryout Research Station, Genetic Resources Department, Desert Research Center, 1 Mathaf El-Matarya St., El-Matareya, Cairo, 11753, Egypt.
Plant Physiol Biochem. 2024 Aug;213:108840. doi: 10.1016/j.plaphy.2024.108840. Epub 2024 Jun 14.
Low-temperature events are one of the leading environmental cues that considerably reduce plant growth and shift species biodiversity. Hydrogen peroxide (HO) is a signaling molecule that has a distinguished role during unfavorable conditions and shows outstanding perspectives in low-temperature stress. Herein, we elucidated the protective role and regulatory mechanism of HO in alleviating the deleterious effects of low-temperature stress in pitaya plants. Micropropagated pitaya plants were cultured in Murashige and Skoog media supplemented with different levels of HO (0, 5, 10, and 20 mM) and then exposed to low-temperature stress (5 °C for 24 h). HO at 10 mM, improved low-temperature stress tolerance by relieving oxidative injuries and ameliorating growth parameters in terms of fresh weight (66.7%), plant length (16.7%), and pigments content viz., chlorophyll a (157.4%), chlorophyll b (209.1%), and carotenoids (225.9%). HO counteracted the low-temperature stress by increasing amino acids (224.7%), soluble proteins (190.5%), and sugars (126.6%). Simultaneously, secondary metabolites like ascorbic acid (ASA), anthocyanins, phenolics, flavonoids, total antioxidant (TOA), and proline were also up-regulated by HO (104.9%, 128.8%, 166.3%, 141.4%, and 436.4%, respectively). These results corresponded to the stimulative role triggered by HO in boosting the activities of catalase (22.4%), ascorbate peroxidase (20.7%), superoxide dismutase (88.4%), polyphenol oxidase (60.7%), soluble peroxidase (23.8%), and phenylalanine ammonia-lyase (57.1%) as well as the expression level of HpCAT, HpAPX, HpSOD, HpPPO, and HpPAL genes, which may help to moderate low-temperature stress. In conclusion, our findings stipulate new insights into the mechanisms by which HO regulates low-temperature stress tolerance in pitaya plants.
低温事件是导致植物生长减缓和物种生物多样性变化的主要环境因素之一。过氧化氢（HO）是一种信号分子，在不利条件下具有显著作用，并在低温胁迫方面显示出出色的前景。本文阐述了 HO 在缓解火龙果植物低温胁迫有害影响中的保护作用和调控机制。在补充不同水平 HO（0、5、10 和 20mM）的 Murashige 和 Skoog 培养基中培养微繁殖的火龙果植物，然后暴露于低温胁迫（24 小时 5°C）下。10mM 的 HO 通过缓解氧化损伤和改善鲜重（66.7%）、植物长度（16.7%）和色素含量（叶绿素 a：157.4%、叶绿素 b：209.1%和类胡萝卜素：225.9%）来提高低温胁迫耐受性。HO 通过增加氨基酸（224.7%）、可溶性蛋白（190.5%）和糖（126.6%）来对抗低温胁迫。同时，HO 还上调了抗坏血酸（ASA）、花青素、酚类、类黄酮、总抗氧化剂（TOA）和脯氨酸等次生代谢物（分别为 104.9%、128.8%、166.3%、141.4%和 436.4%）。这些结果与 HO 触发的刺激作用相对应，该作用促进了过氧化氢酶（22.4%）、抗坏血酸过氧化物酶（20.7%）、超氧化物歧化酶（88.4%）、多酚氧化酶（60.7%）、可溶性过氧化物酶（23.8%）和苯丙氨酸解氨酶（57.1%）的活性以及 HpCAT、HpAPX、HpSOD、HpPPO 和 HpPAL 基因的表达水平的提高，这有助于缓解低温胁迫。总之，本研究结果为 HO 调节火龙果植物低温胁迫耐受性的机制提供了新的见解。
