Genes encoding members of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) gene family from Azadirachta indica and correlation with azadirachtin biosynthesis

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• 作者：Sweta Bhambhani ; Deepika Lakhwani ; Tapsi Shukla…
• 关键词：Azadirachta indica ; Azadirachtin ; Escherichia coli ; HMGR ; MVA pathway
• 刊名：Acta Physiologiae Plantarum
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：39
• 期：2
• 全文大小：
• 刊物主题：Plant Physiology; Plant Genetics & Genomics; Plant Biochemistry; Plant Pathology; Plant Anatomy/Development; Agriculture;
• 出版者：Springer Berlin Heidelberg
• ISSN：1861-1664
• 卷排序：39

文摘

Azadirachta indica (A. Juss) commonly known as Neem is an important source of valuable natural products and occupies an important place in traditional healthcare system. Naturally, this plant synthesizes a number of tetranortriterpenoids utilizing isoprenoid as substrate flux. Although various phytochemical and pharmacological studies in A. indica have been carried out, but very limited information is available about the biosynthetic pathway as well as structural and regulatory genes involved in synthesis of bioactive molecules. In this study, we have cloned and characterized two genes, AiHMGR1 and AiHMGR2, encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR; EC 1.1.1.34) catalyzing the rate limiting step of the isoprenoid biosynthesis. Two isoforms, AiHMGR1 and AiHMGR2, contain an open reading frame of 1707 and 1695 bp encoding polypeptides of 568 and 545 amino acid residues, respectively. The nucleotide and encoded amino acid sequence analyses suggest that both genes encode polypeptides with necessary structural domains present in other plant HMGRs, however, have different genomic organization. The relative expression analysis suggests that two genes express differentially in various tissues. Out of the two genes, expression of AiHMGR2 showed a direct correlation with azadirachtin accumulation in fruit tissue. The common as well as unique cis-regulatory elements present in both genes might be responsible for differential expression of both the genes in various tissues. The color complementation assay in Escherichia coli suggests that though both AiHMGR1 and AiHMGR2 encode functional proteins, AiHMGR2 is more active as compared to AiHMGR1.