CSIR-Central Institute of Medicinal and Aromatic Plants, PO CIMAP, Lucknow 226 015, India.
Plant J. 2012 Aug;71(4):539-49. doi: 10.1111/j.1365-313X.2012.05006.x. Epub 2012 Jun 12.
Whole genome duplication leads to autopolyploidy and brings about an increase in cell size, concentration of secondary metabolites and enhanced cytosine methylation. The increased cell size offers a positive advantage to polyploids for cell-surface-related activities, but there is a differential response to change in body size across species and taxonomic groups. Although polyploidy has been very extensively studied, having genetic, ecological and evolutionary implications, there is no report that underscores the significance of native secondary metabolites vis-à-vis body size with ploidy change. To address this problem we targeted unique diploid-autotetraploid paired sets of eight diverse clones of six species of Cymbopogon- a species complex of aromatic grasses that accumulate qualitatively different monoterpene essential oils (secondary metabolite) in their vegetative biomass. Based on the qualitative composition of essential oils and the plant body size relationship between the diploid versus autotetraploid paired sets, we show that polyploidy brings about enhanced accumulation of secondary metabolites in all cases, but exerts differential effects on body size in various species. It is observed that the accumulation of alcohol-type metabolites (e.g. geraniol) does not inhibit increase in body size with ploidy change from 2× to 4× (r = 0.854, P < 0.01), but aldehyde-type metabolites (e.g. citral) appear to drastically impede body development (r = -0.895). Such a differential response may be correlated to the metabolic steps involved in the synthesis of essential oil components. When changed to tetraploidy, the progenitor diploids requiring longer metabolic steps in production of their secondary metabolites are stressed, and those having shorter metabolite routes better utilize their resources for growth and vigour. In situ immunodetection of 5-methylcytosine sites reveals enhanced DNA methylation in autopolyploids. It is underpinned that the qualitative composition of secondary metabolites found in the vegetative biomass of the progenitor diploid has a decisive bearing on the body size of the derived autotetraploids and brings about an enhancement in genome-wide cytosine methylation.
全基因组复制导致同源多倍体，并导致细胞大小增加、次生代谢物浓度增加和胞嘧啶甲基化增强。增加的细胞大小为多倍体的细胞表面相关活动提供了积极的优势，但在不同物种和分类群中，对体型变化的反应是不同的。虽然多倍体已经被广泛研究，具有遗传、生态和进化意义，但没有报道强调原生次生代谢物与多倍体变化的体型之间的关系。为了解决这个问题，我们针对六个物种的 8 个不同克隆的独特二倍体-同源四倍体配对集，这些克隆属于芳香草的 Cymbopogon 种复合体，在其营养生物量中积累定性不同的单萜类精油（次生代谢物）。基于精油的定性组成和二倍体与同源四倍体配对集之间的植物体型关系，我们表明多倍体在所有情况下都会导致次生代谢物的积累增强，但在不同物种中对体型产生不同的影响。观察到醇型代谢物（例如香叶醇）的积累不会抑制从 2×到 4×的多倍体变化引起的体型增加（r = 0.854，P < 0.01），但醛型代谢物（例如柠檬醛）似乎严重阻碍了身体发育（r = -0.895）。这种差异反应可能与参与合成精油成分的代谢步骤有关。当转变为四倍体时，产生次生代谢物需要更长代谢步骤的原始二倍体受到压力，而那些具有更短代谢途径的代谢物更好地利用其资源进行生长和活力。原位免疫检测 5-甲基胞嘧啶位点揭示同源多倍体中的 DNA 甲基化增强。可以看出，在原始二倍体营养生物量中发现的次生代谢物的定性组成对衍生同源四倍体的体型有决定性影响，并导致全基因组胞嘧啶甲基化增强。
