JEB：鉴定出大麻活性物质生物合成路径
研究人员在无毒大麻开发方面取得了新的进展。美国明尼苏达大学的一组科学家成功鉴定出大麻精神活性物质四氢大麻酚酸（THCA）生物合成路径中几乎所有的相关基因。知道了这些基因，科学家就可以通过不同的方法使其沉默，例如RNA干绕。这些研究人员说，对这些基因进行研究还可能得到新的药物以治疗疼痛和眩晕。
Marks和他的同事在Journal of ExperimentalBotany报道了他们的结果。他们发现这些基因在大麻花表面绒毛中的表达量很高，并且鉴定出其中的特异性聚酮合酶基因。在marijuana品种的绒毛中，THCA的积累量较高，而hemp品种中的含量很低。
Hemp中THCA的含量在0.3%以下，而marijuana中THCA的平均含量高达30%。Hemp曾经一度是很流行的作物，它是高强度工业纤维和营养油的一个重要来源。但在药物法规颁布以后，由于担心有人会利用hemp来掩盖marijuana，因此禁止了这种作物的种植。
这些发现对啤酒业也具有重要作用。研究人员称，大麻植物中的聚酮合酶基因与啤酒花中的基因非常相似。啤酒花能产生律草酮和黄腐酚，前者使啤酒产生独特的苦味，而后者具有多种健康功效。科学家称，这两种物质的生物合成路径与THCA几乎完全一致。因此，研究大麻基因有助于理解啤酒花的生化途径。（生物谷Bioon.com）
生物谷推荐原始出处：
Journal of Experimental Botany 2009 60(13):3715-3726;doi:10.1093/jxb/erp210
Identification of candidate genesaffecting Δ9-tetrahydrocannabinol biosynthesis inCannabis sativa
M. David Marks1,*, Li Tian2 , Jonathan P.Wenger1, Stephanie N. Omburo1, Wilfredo Soto-Fuentes1, Ji He2,David R. Gang3, George D. Weiblen1 and Richard A. Dixon2
1Department of Plant Biology, University of Minnesota, 1445Gortner Ave, St Paul, MN 55108, USA
2Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore,OK 73401, USA
3Department of Plant Sciences, University of Arizona, Tucson, AZ85721-0036, USA
RNA isolated from the glands of aΔ9-tetrahydrocannabinolic acid (THCA)-producing strainof Cannabis sativa was used to generate a cDNA library containingover 100 000 expressed sequence tags (ESTs). Sequencing of over2000 clones from the library resulted in the identification of over1000 unigenes. Candidate genes for almost every step in thebiochemical pathways leading from primary metabolites to THCA wereidentified. Quantitative PCR analysis suggested that many of thepathway genes are preferentially expressed in the glands.Hexanoyl-CoA, one of the metabolites required for THCA synthesis,could be made via either de novo fatty acids synthesis or via thebreakdown of existing lipids. qPCR analysis supported the de novopathway. Many of the ESTs encode transcription factors and twoputative MYB genes were identified that were preferentiallyexpressed in glands. Given the similarity of the Cannabis MYB genesto those in other species with known functions, these Cannabis MYBsmay play roles in regulating gland development and THCA synthesis.Three candidates for the polyketide synthase (PKS) gene responsiblefor the first committed step in the pathway to THCA werecharacterized in more detail. One of these was identical to apreviously reported chalcone synthase (CHS) and was found to haveCHS activity. All three could use malonyl-CoA and hexanoyl-CoA assubstrates, including the CHS, but reaction conditions were notidentified that allowed for the production of olivetolic acid (theproposed product of the PKS activity needed for THCA synthesis).One of the PKS candidates was highly and specifically expressed inglands (relative to whole leaves) and, on the basis of theseexpression data, it is proposed to be the most likely PKSresponsible for olivetolic acid synthesis in Cannabis glands.