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Open Access Research article

Functional analysis of the omega-6 fatty acid desaturase (CaFAD2) gene family of the oil seed crop Crambe abyssinica

Jihua Cheng12, Li-Hua Zhu3, Elma MJ Salentijn1, Bangquan Huang2, Jens Gruber4, Annemarie C Dechesne1, Frans A Krens1, Weicong Qi12, Richard GF Visser1 and Eibertus N van Loo1*

Author Affiliations

1 Wageningen UR Plant Breeding, P.O. Box 16, 6700, AA Wageningen, The Netherlands

2 College of Life Science, Hubei University, Wuhan, People’s Republic of China

3 Plant Breeding and Biotechnology, Swedish University of Agricultural Science, Alnarp, Sweden

4 Institute for Biology I-Botany, RWTH Aachen University, Aachen, Germany

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BMC Plant Biology 2013, 13:146  doi:10.1186/1471-2229-13-146

Published: 1 October 2013

Abstract

Background

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.

Results

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.

Conclusions

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.

Keywords:
Crambe abyssinica; Fatty acid desaturase 2; Oil crop; Oleic acid; Polyunsaturated fatty acid; RNAi; Gene expression