外源2,4-表油菜素内酯对镉胁迫下草地早熟禾叶绿素代谢的影响

Effect of Exogenous 2,4-Epibrassinolide on the Chlorophyll Metabolism of Kentucky Bluegrass under Cd Stress

本研究以草地早熟禾(Poa pratensis)‘午夜’幼苗为试验材料,研究镉(Cadmium,Cd)胁迫下及不同浓度(5,50,100 nM)的2,4-表油菜素内酯(2,4-Epibrassinolide,EBR)对0.5 mM CdCl 2胁迫下草地早熟禾叶片的叶绿素代谢途径的影响。研究结果表明,Cd胁迫1 d后可诱导PpPBGD,PpCHLD,PpCHLI和PpPOR基因的下调表达和PpCLH,PpPPH,PpPAO和PpRCCR基因的上调表达。50 nM的EBR可显著提高Cd胁迫下原卟啉Ⅳ、镁-原卟啉Ⅳ、原叶绿素酸酯、叶绿素a和总叶绿素的含量,到Cd胁迫6 d时,这些指标与未胁迫对照无显著差异,这可能与外源EBR诱导的叶绿素生物合成基因的上调表达和降解通路的下调表达有关。因此,外源EBR可通过诱导叶绿素生物合成通路基因的上调表达来缓解Cd胁迫引起的叶绿素中间产物转化的受阻程度,以及通过诱导降解通路基因的下调表达来减缓叶绿素的降解,进而使得Cd胁迫下草地早熟禾叶片叶绿素含量维持相对较高的水平。

In the present study,Kentucky bluegrass‘Midnight’seedlings were used as experimental materials to study the chlorophyll metabolism pathways of leaves under Cd stress and different concentrations of 2,4-epibrassinolide(EBR:5,50,100 nM)with 0.5 mM CdCl 2 stress.The results showed that Cd stress induced the down-regulated expression of PpPBGD,PpCHLD,PpCHLI and PpPOR genes and the up-regulated expression of PpCLH,PpPPH,PpPAO and PpRCCR genes after 1 day.The application of 50 nM EBR significantly increased protoporphyrin Ⅳ,Mg-protoporphyrin Ⅳ,protochlorophyllide,chlorophyll a and total chlorophyll contents within Cd stress.After 6 days of Cd stress,the content of these indicators of 50nM EBR-treated seedlings had no significant difference with the control,which might be attributed to the upregulation of chlorophyll biosynthetic genes and degradative genes.The results indicated that the alleviative effect on the decline of chlorophyll content were associated with that the exogenous EBR induced the upregulation expression of genes involved in chlorophyll biosynthetic genes and the downregulation expression of genes involved in chlorophyll degradation.