Mechanisms of Molecular Regulation of Nicotine Biosynthesis

尼古丁生物碱是在烟草属植物的根中合成的，经过虫害、伤害和茉莉酸处理后，其合成增加。腐胺N-甲基转移酶(PMT)催化尼古丁生物合成的第一步。本研究报道了三个烟草PMT基因(NsPMT1、NsPMT2和NsPMT3)和一个烟草A622基因的表达模式。NsPMT和A622基因的转录本仅在根中检测到，并被茉莉酸甲酯处理上调。乙烯拮抗茉莉酸诱导的基因表达。当NsPMT1、NsPMT2、NsPMT3和A622的5‘侧翼区域独立地与β-葡萄糖醛酸酶报告基因融合后，导入的转基因基因在根的皮层、内皮层和木质部表达，并被茉莉酸甲酯处理上调。NsPMT基因的这些定性相似的表达模式是在其5‘侧翼区仅0.25kb的情况下实现的，其中包含在这四个基因之间保守的短DNA序列。

Nicotine alkaloids are synthesized in the root of Nicotiana species, and their synthesis increases after insect attack, wounding and jasmonate treatment of the leaf. Putrescine N-methyltransferase (PMT) catalyzes the first committed step in nicotine biosynthesis. The expression patterns of the three Nicotiana sylvestris PMT genes (NsPMT1, NsPMT2, and NsPMT3) and of one Nicotiana sylvestris A622 gene are reported upon in this study. Transcripts of the NsPMT and A622 genes were detected only in the root, and were up-regulated by methyl jasmonate treatment. Ethylene antagonized the gene induction by jasmonate. When the 5'-flanking regions of NsPMT1, NsPMT2, NsPMT3 and A622 were fused independently to a β-glucuronidase reporter gene and introduced transgenes were expressed in the cortex, endodermis, and xylem in the root, as well as upregulated by methyl jasmonate treatment. These qualitatively similar patterns of expression for the NsPMT genes are achieved with only 0.25 kb of their 5'-flanking regions, which contain a short DNA sequence conserved among these four genes.