Eady Colin C, Kamoi Takahiro, Kato Masahiro, Porter Noel G, Davis Sheree, Shaw Martin, Kamoi Akiko, Imai Shinsuke
National Centre for Advanced Bio-Protection Technologies, Lincoln University, Christchurch 7647, New Zealand.
Plant Physiol. 2008 Aug;147(4):2096-106. doi: 10.1104/pp.108.123273. Epub 2008 Jun 26.
Through a single genetic transformation in onion (Allium cepa), a crop recalcitrant to genetic transformation, we suppressed the lachrymatory factor synthase gene using RNA interference silencing in six plants. This reduced lachrymatory synthase activity by up to 1,544-fold, so that when wounded the onions produced significantly reduced levels of tear-inducing lachrymatory factor. We then confirmed, through a novel colorimetric assay, that this silencing had shifted the trans-S-1-propenyl-l-cysteine sulfoxide breakdown pathway so that more 1-propenyl sulfenic acid was converted into di-1-propenyl thiosulfinate. A consequence of this raised thiosulfinate level was a marked increase in the downstream production of a nonenzymatically produced zwiebelane isomer and other volatile sulfur compounds, di-1-propenyl disulfide and 2-mercapto-3,4-dimethyl-2,3-dihydrothiophene, which had previously been reported in trace amounts or had not been detected in onion. The consequences of this dramatic simultaneous down- and up-regulation of secondary sulfur products on the health and flavor attributes of the onion are discussed.
通过对洋葱（葱属植物）这一遗传转化顽固的作物进行单次遗传转化，我们利用RNA干扰沉默技术在六株植物中抑制了催泪因子合酶基因。这使催泪合酶活性降低了多达1544倍，因此当洋葱受到损伤时，产生的诱导流泪的催泪因子水平显著降低。然后，我们通过一种新型比色测定法证实，这种沉默改变了反式-S-1-丙烯基-L-半胱氨酸亚砜的分解途径，从而使更多的1-丙烯基亚磺酸转化为二-1-丙烯基硫代亚磺酸盐。这种硫代亚磺酸盐水平升高的一个结果是，非酶促产生的二烯丙基硫醚异构体和其他挥发性硫化合物——二-1-丙烯基二硫化物和2-巯基-3,4-二甲基-2,3-二氢噻吩的下游产量显著增加，这些化合物此前在洋葱中仅以痕量形式被报道过或未被检测到。本文讨论了这种次生硫产物同时大幅下调和上调对洋葱健康和风味特性的影响。
