Wageningen UR Plant Breeding, P,O, Box 16, 6700, AA Wageningen, The Netherlands.
BMC Plant Biol. 2013 Oct 1;13:146. doi: 10.1186/1471-2229-13-146.
Crambe abyssinica produces high erucic acid (C22:1, 55-60%) in the seed oil, which can be further increased by reduction of polyunsaturated fatty acid (PUFA) levels. The omega-6 fatty acid desaturase enzyme (FAD2) is known to be involved in PUFA biosynthesis. In crambe, three CaFAD2 genes, CaFAD2-C1, CaFAD2-C2 and CaFAD2-C3 are expressed.
The individual effect of each CaFAD2 gene on oil composition was investigated through studying transgenic lines (CaFAD2-RNAi) for differential expression levels in relation to the composition of seed-oil. Six first generation transgenic plants (T1) showed C18:1 increase (by 6% to 10.5%) and PUFA reduction (by 8.6% to 10.2%). The silencing effect in these T1-plants ranged from the moderate silencing (40% to 50% reduction) of all three CaFAD2 genes to strong silencing (95% reduction) of CaFAD2-C3 alone. The progeny of two T1-plants (WG4-4 and WG19-6) was further analysed. Four or five transgene insertions are characterized in the progeny (T2) of WG19-6 in contrast to a single insertion in the T2 progeny of WG4-4. For the individual T2-plants of both families (WG19-6 and WG4-4), seed-specific silencing of CaFAD2-C1 and CaFAD2-C2 was observed in several individual T2-plants but, on average in both families, the level of silencing of these genes was not significant. A significant reduction in expression level (P < 0.01) in both families was only observed for CaFAD2-C3 together with significantly different C18:1 and PUFA levels in oil.
CaFAD2-C3 expression is highly correlated to levels of C18:1 (r = -0.78) and PUFA (r = 0.75), which suggests that CaFAD2-C3 is the most important one for changing the oil composition of crambe.
芝麻菜种子油中含有高含量的芥酸（C22:1，55-60％），通过降低多不饱和脂肪酸（PUFA）水平可以进一步增加芥酸。ω-6 脂肪酸去饱和酶（FAD2）已知参与 PUFA 生物合成。在芝麻菜中，有三个 CaFAD2 基因，CaFAD2-C1、CaFAD2-C2 和 CaFAD2-C3 表达。
通过研究与种子油成分相关的差异表达水平的转基因系（CaFAD2-RNAi），研究了每个 CaFAD2 基因对油成分的单独影响。六个第一代转基因植物（T1）表现出 C18:1 增加（增加 6％至 10.5％）和 PUFA 减少（减少 8.6％至 10.2％）。这些 T1 植物中的沉默效果范围从所有三个 CaFAD2 基因的中度沉默（减少 40％至 50％）到单独 CaFAD2-C3 的强沉默（减少 95％）。两个 T1 植物（WG4-4 和 WG19-6）的后代进一步进行了分析。在 WG19-6 的后代（T2）中，有四个或五个转基因插入物被表征，而在 WG4-4 的 T2 后代中只有一个插入物。对于两个家族（WG19-6 和 WG4-4）的各个 T2 植物，在几个单独的 T2 植物中观察到 CaFAD2-C1 和 CaFAD2-C2 的种子特异性沉默，但在两个家族中，这些基因的沉默水平没有显著差异。只有在两个家族中，CaFAD2-C3 的表达水平显著降低（P<0.01），同时油中的 C18:1 和 PUFA 水平也显著降低。
CaFAD2-C3 的表达与 C18:1（r=-0.78）和 PUFA（r=-0.75）水平高度相关，这表明 CaFAD2-C3 是改变芝麻菜油成分的最重要因素。
