School of Biotechnology and Food Engineering, Hefei University of Technology, Hefei 230009, People's Republic of China; College of Life Science, Hebei University, Baoding 071002, People's Republic of China.
J Plant Physiol. 2009 Dec 15;166(18):2013-22. doi: 10.1016/j.jplph.2009.06.008. Epub 2009 Jul 21.
In the present paper, a correlation between enhanced conversion of protocorm-like bodies (PLBs) of Dendrobium huoshanense to shoots by free polyamines (PAs) and changes in the levels of endogenous hormones is described. The endogenous levels of free spermidine (Spd) and putrescine (Put) increased during the conversion of PLBs to shoots. The exogenous addition of PAs, mainly Spd or Put at 2.0mM, not only elevated the endogenous levels of PAs but also promoted the frequency of conversion of PLBs to shoots. As compared with control, the enhanced conversion of PLBs to shoots by exogenous PAs was accompanied by an increase in ratio of total cytokinins (CTKs) to indole-3-acetic acid (IAA), which was due to decrease in the endogenous level of IAA and increase in the endogenous level of total CTKs, including the levels of isopentenyladenine+isopentenyladenine 9-riboside and zeatin+zeatin riboside. Analysis of enzyme activities showed that the increased endogenous level of total CTKs by PAs was related to the inhibition of CTK decomposition by CTK oxidase, while the decreased endogenous level of IAA was related to the promotion of IAA decomposition by IAA oxidase. Addition of PA biosynthetic inhibitors, involving alpha-difluoromethylornithine for Put and methylglyoxal(bis)-guanylhydrazone for Spd and Spm, decreased the conversion of PLBs to shoots, the ratio of total CTKs to IAA, and the levels of endogenous Put and Spd. This inhibition could be partly reversed by the application of exogenous Put or Spd.
本文描述了霍山石斛原球茎（protocorm-like bodies，PLBs）向芽的高效转化与游离多胺（polyamines，PAs）水平变化之间的相关性。在 PLBs 向芽的转化过程中，游离亚精胺（spermidine，Spd）和腐胺（putrescine，Put）的内源水平增加。添加外源多胺（主要是 2.0mM 的 Spd 或 Put）不仅提高了 PAs 的内源水平，而且促进了 PLBs 向芽的转化频率。与对照相比，外源多胺促进 PLBs 向芽的高效转化伴随着细胞分裂素（cytokinins，CTKs）与吲哚-3-乙酸（indole-3-acetic acid，IAA）总量之比的增加，这归因于内源 IAA 水平的降低和内源 CTKs 总量的增加，包括异戊烯基腺嘌呤+异戊烯基腺嘌呤 9-核糖苷和玉米素+玉米素核苷的水平。酶活性分析表明，PAs 增加的 CTKs 内源水平与 CTK 氧化酶对 CTK 分解的抑制有关，而内源 IAA 水平的降低与 IAA 氧化酶促进 IAA 分解有关。添加 PA 生物合成抑制剂，包括用于 Put 的α-二氟甲基鸟氨酸和用于 Spd 和 Spm 的甲基乙二醛（bis）-鸟苷腙，降低了 PLBs 向芽的转化率、CTKs 与 IAA 总量之比以及内源 Put 和 Spd 的水平。该抑制作用可部分通过添加外源 Put 或 Spd 得到逆转。
