Chakraborty Shreosi, Raychaudhuri Sarmistha Sen
Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, 92, APC Road, Kolkata, 700 009, India.
Plant Cell Rep. 2025 Jan 27;44(2):39. doi: 10.1007/s00299-025-03424-x.
Melatonin increases Pb tolerance in P. ovata seedlings via the regulation of growth and stress-related phytohormones, ROS scavenging and genes responsible for melatonin synthesis, metal chelation, and stress defense. Lead (Pb) is a highly toxic heavy metal that accumulates in plants through soil and air contamination and impairs its plant growth and development. Because of its pharmaceutical importance, improvements in Plantago ovata yield against abiotic stresses are necessary. Melatonin (MEL) is a stress-alleviating biostimulator and our results showed a reduction in Pb induced phytotoxicity by enhancing plant growth attributes and balancing protective osmolytes. Pb-induced reactive oxygen species accumulation, including superoxide and peroxide free radicals and their mitigation through enzymatic antioxidants, was demonstrated in presence of MEL. Cell viability and Pb bioaccumulation were determined to understand the extent of cellular damage. Moreover, MEL increased secondary metabolite (flavonoids and anthocyanins) contents by 2-3-fold at the lowest Pb concentrations. Similar increases in the relative expression of genes (PoPAL and PoPPO), which are responsible for the production of non-enzymatic antioxidants, were observed. Notably, the upregulation of the PoCOMT gene up to 4-fold indicates increased melatonin production, as manifested in the phytomelatonin level. MEL supplementation also increased the auxin (IAA) level by 3-fold in the 100 µM Pb treatment group, while the abscisic acid (ABA) level decreased (1.4-fold) and the expression of PoMYB (a stress-related transcription factor) increased (up to 2.66-fold). Additionally, we found extreme downregulation (up to 18-fold) in the relative expression of PoMT 2 (a metal binding thiol compound) with melatonin treatment, which is otherwise upregulated (by 6-fold) during Pb stress. In the current study, these effects collectively revealed that MEL contribute to enhanced plant growth and Pb stress tolerance.
褪黑素通过调节生长和与胁迫相关的植物激素、活性氧清除以及负责褪黑素合成、金属螯合和胁迫防御的基因，提高了卵叶车前幼苗对铅的耐受性。铅（Pb）是一种剧毒重金属，通过土壤和空气污染在植物中积累，损害植物的生长发育。由于其药用价值，提高卵叶车前在非生物胁迫下的产量很有必要。褪黑素（MEL）是一种缓解胁迫的生物刺激剂，我们的结果表明，通过增强植物生长特性和平衡保护性渗透物质，可降低铅诱导的植物毒性。在褪黑素存在的情况下，证明了铅诱导的活性氧积累，包括超氧化物和过氧化物自由基，以及通过酶促抗氧化剂对其的缓解。通过测定细胞活力和铅生物积累来了解细胞损伤程度。此外，在最低铅浓度下，褪黑素使次生代谢产物（类黄酮和花青素）含量增加了2至3倍。观察到负责非酶促抗氧化剂产生的基因（PoPAL和PoPPO）的相对表达也有类似增加。值得注意的是，PoCOMT基因上调至4倍表明褪黑素产量增加，这在植物褪黑素水平上有所体现。在100µM铅处理组中，补充褪黑素还使生长素（IAA）水平提高了3倍，而脱落酸（ABA）水平下降（1.4倍），PoMYB（一种与胁迫相关的转录因子）的表达增加（高达2.66倍）。此外，我们发现，用褪黑素处理后，PoMT 2（一种金属结合硫醇化合物）的相对表达极度下调（高达18倍），而在铅胁迫期间该基因会上调（6倍）。在本研究中，这些效应共同表明褪黑素有助于增强植物生长和对铅胁迫的耐受性。
