Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Zwirki i Wigury 101, 02-093 Warszawa, Poland.
Chemistry Department, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico.
Molecules. 2020 Apr 3;25(7):1644. doi: 10.3390/molecules25071644.
Relatively few studies have been focused so far on magnesium-isotope fractionation during plant growth, element uptake from soil, root-to-leaves transport and during chlorophylls biosynthesis. In this work, maize and garden cress were hydroponically grown in identical conditions in order to examine if the carbon fixation pathway (C4, C3, respectively) might have impact on Mg-isotope fractionation in chlorophyll-a. The pigment was purified from plants extracts by preparative reversed phase chromatography, and its identity was confirmed by high-resolution mass spectrometry. The green parts of plants and chlorophyll-a fractions were acid-digested and submitted to ion chromatography coupled through desolvation system to multiple collector inductively coupled plasma-mass spectrometry. Clear preference for heavy Mg-isotopes was found in maize green parts (∆Mg 0.65, 0.74 for two biological replicates, respectively) and in chlorophyll-a (∆Mg 1.51, 2.19). In garden cress, heavy isotopes were depleted in green parts (∆Mg (-0.87)-(-0.92)) and the preference for heavy isotopes in chlorophyll-a was less marked relative to maize (∆Mg 0.55-0.52). The observed effect might be ascribed to overall higher production of energy in form of adenosine triphosphate (ATP), required for carbon fixation in C4 compared to C3, which could reduce kinetic barrier and make equilibrium fractionation prevailing during magnesium incorporation to protoporphyrin ring.
迄今为止，相对较少的研究集中在植物生长过程中镁同位素分馏、从土壤中元素吸收、根到叶的运输以及叶绿素生物合成过程中镁同位素分馏上。在这项工作中，玉米和荠菜在相同条件下进行水培生长，以检验固碳途径（分别为 C4、C3）是否会影响叶绿素-a 中的镁同位素分馏。通过制备性反相色谱法从植物提取物中纯化色素，并通过高分辨率质谱法确认其身份。通过酸消解植物的绿色部分和叶绿素-a 部分，并通过脱溶剂系统将其提交给离子色谱，与多收集器电感耦合等离子体质谱联用。在玉米的绿色部分（分别为 0.65 和 0.74，两个生物学重复）和叶绿素-a 中发现了对重镁同位素的明显偏好（∆Mg 0.65，0.74）。在荠菜中，绿色部分中重同位素被耗尽（∆Mg（-0.87）-（-0.92）），与玉米相比，叶绿素-a 中对重同位素的偏好程度较低（∆Mg 0.55-0.52）。观察到的效应可能归因于 C4 中固定碳所需的三磷酸腺苷（ATP）形式的能量总体上更高，这可以降低动力学障碍，使镁掺入原卟啉环过程中的平衡分馏占主导地位。
