<i><span style="font-family:Verdana;">Centella asiatica </span></i><span style="font-family:""><span style="font-family:Verdana;">(L.) is one of t...<i><span style="font-family:Verdana;">Centella asiatica </span></i><span style="font-family:""><span style="font-family:Verdana;">(L.) is one of the most valuable medicinal plants since preh</span><span style="font-family:Verdana;">istoric times. The pharmaceutical importance of this herb is due to the accumulation of large quantities of pentacyclic triterpenoid saponins, collectively known as centelloids synthesized by the isoprenoid biosynthesis</span><span style="font-family:Verdana;"> path</span><span style="font-family:Verdana;">way. Biosynthesis of triterpenoid in the plants proceeds via either of the tw</span><span style="font-family:Verdana;">o pathways, viz. Mevalonate (MVA) pathway (in the cytosol) or 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway (in plastid). In </span><i><span style="font-family:Verdana;">Centella</span></i><span style="font-family:Verdana;">, the pathway leading to the accumulation of triterpenoid is still not known or elucidated. Thus, to know whether the MVA or MEP pathway or a cross-talk between the pathway leads to the biosynthesis of triterpenoid, silencing the key regulatory gene using RNAi tool, of each of the pathway and then analyze a metabolite is an efficient approach. The key regulatory enzyme of the MVA pathway </span><i><span style="font-family:Verdana;">i.e</span></i><span style="font-family:Verdana;">. 3-</span><i><span style="font-family:Verdana;">Hydroxy</span></i><span style="font-family:Verdana;">-3-</span><i><span style="font-family:Verdana;">methylglutaryl-coenzyme A reductase</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">HMGR</span></i><span style="font-family:Verdana;">) has already been successfully silenced using RNAi tool</span></span><span style="font-family:Verdana;"> <a href="#ref1">[1]</a></span><span style="font-family:""><span style="font-family:Verdana;">. In the present study, the 1-</span><i><span style="font-family:Verdana;">deoxy-D-xylulose</span></i><span style="font-family:Verdana;">-5-</span><i><span style="font-family:Verdana;">phosphate reductoisomerase</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">DXR</span></i><span style="font-family:Verdana;">) a key regulatory enzyme in MEP pathway is silenced. The RNAi-</span><i><span style="font-family:Verdana;">DXR</span></i><span style="font-family:Verdana;"> construct in pHANNIBAL vector was cloned into a binary vector pART27 and subsequently transformed into </span><i><span style="font-family:Verdana;">Agrobacterium</span></i><span style="font-family:Verdana;"> strain AGL1. The transient analysis of the RNAi-</span><i><span style="font-family:Verdana;">CaDXR</span></i><span style="font-family:Verdana;"> using semi-quantitative RT-PCR confirmed the silencing of the endogenous DXR gene in </span><i><span style="font-family:Verdana;">Nicotiana</span></i><span style="font-family:Verdana;"> and further confirmed in </span><i><span style="font-family:Verdana;">Centella asiatica</span></i><span style="font-family:Verdana;">. The present study is the first step aimed to delineate the MEP pathway using RNAi silencing approach to elucidate its role in the accumulation of triterpenoid in this important medicinal plant.展开更多
文摘<i><span style="font-family:Verdana;">Centella asiatica </span></i><span style="font-family:""><span style="font-family:Verdana;">(L.) is one of the most valuable medicinal plants since preh</span><span style="font-family:Verdana;">istoric times. The pharmaceutical importance of this herb is due to the accumulation of large quantities of pentacyclic triterpenoid saponins, collectively known as centelloids synthesized by the isoprenoid biosynthesis</span><span style="font-family:Verdana;"> path</span><span style="font-family:Verdana;">way. Biosynthesis of triterpenoid in the plants proceeds via either of the tw</span><span style="font-family:Verdana;">o pathways, viz. Mevalonate (MVA) pathway (in the cytosol) or 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway (in plastid). In </span><i><span style="font-family:Verdana;">Centella</span></i><span style="font-family:Verdana;">, the pathway leading to the accumulation of triterpenoid is still not known or elucidated. Thus, to know whether the MVA or MEP pathway or a cross-talk between the pathway leads to the biosynthesis of triterpenoid, silencing the key regulatory gene using RNAi tool, of each of the pathway and then analyze a metabolite is an efficient approach. The key regulatory enzyme of the MVA pathway </span><i><span style="font-family:Verdana;">i.e</span></i><span style="font-family:Verdana;">. 3-</span><i><span style="font-family:Verdana;">Hydroxy</span></i><span style="font-family:Verdana;">-3-</span><i><span style="font-family:Verdana;">methylglutaryl-coenzyme A reductase</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">HMGR</span></i><span style="font-family:Verdana;">) has already been successfully silenced using RNAi tool</span></span><span style="font-family:Verdana;"> <a href="#ref1">[1]</a></span><span style="font-family:""><span style="font-family:Verdana;">. In the present study, the 1-</span><i><span style="font-family:Verdana;">deoxy-D-xylulose</span></i><span style="font-family:Verdana;">-5-</span><i><span style="font-family:Verdana;">phosphate reductoisomerase</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">DXR</span></i><span style="font-family:Verdana;">) a key regulatory enzyme in MEP pathway is silenced. The RNAi-</span><i><span style="font-family:Verdana;">DXR</span></i><span style="font-family:Verdana;"> construct in pHANNIBAL vector was cloned into a binary vector pART27 and subsequently transformed into </span><i><span style="font-family:Verdana;">Agrobacterium</span></i><span style="font-family:Verdana;"> strain AGL1. The transient analysis of the RNAi-</span><i><span style="font-family:Verdana;">CaDXR</span></i><span style="font-family:Verdana;"> using semi-quantitative RT-PCR confirmed the silencing of the endogenous DXR gene in </span><i><span style="font-family:Verdana;">Nicotiana</span></i><span style="font-family:Verdana;"> and further confirmed in </span><i><span style="font-family:Verdana;">Centella asiatica</span></i><span style="font-family:Verdana;">. The present study is the first step aimed to delineate the MEP pathway using RNAi silencing approach to elucidate its role in the accumulation of triterpenoid in this important medicinal plant.
