RESUMEN
Understanding the quantitative control of fatty acid desaturation during the biosynthesis of seed storage oil has become a priority area for research, as a consequence of its importance for both human health and the substitution of mineral oil for industrial applications. We have analysed the genome structure of two mutants in Arabidopsis thaliana that show substantially elevated content of the omega-3 polyunsaturated fatty acid linolenic acid in their seed oil. In one, rfc4, sequences totalling approximately 2 Mb from chromosome 2 have been duplicated and inserted into chromosome 3. In the other mutant, ife, chromosome 2 sequences totalling approximately 1.4 Mb have been duplicated and inserted into a linked position. In both cases, the duplications encompass the FAD3 locus, which encodes the linoleate desaturase responsible for the biosynthesis of linolenic acid for accumulation in seed storage oil. The results show that mutagens such as fast neutrons (used for the induction of rfc4) and T-DNA (used for the induction of ife, which is not linked to the T-DNA present in the line) can result in the duplication of very large genome segments. They also show that increasing the dosage of the FAD3-containing genomic region results in an increase in the linolenic acid content of seed oil. Consequently, screening methods for duplication of FAD3 orthologues in oil crops may be an appropriate approach for the identification of germplasm for breeding varieties with increased proportions of linolenic acid in the oil that they produce.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Duplicación Cromosómica , Ácido Graso Desaturasas/genética , Genoma de Planta , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Mapeo Cromosómico , Cromosomas de las Plantas/genética , Cromosomas de las Plantas/metabolismo , Clonación Molecular , Cruzamientos Genéticos , ADN de Plantas/genética , ADN de Plantas/metabolismo , Neutrones Rápidos , Ácido Graso Desaturasas/metabolismo , Técnicas de Inactivación de Genes , Genes de Plantas , Sitios Genéticos , Mutagénesis Insercional , Aceites de Plantas/metabolismo , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , Regiones Promotoras Genéticas , Proteínas de Almacenamiento de Semillas/genética , Proteínas de Almacenamiento de Semillas/metabolismo , Semillas/genética , Semillas/metabolismo , Análisis de Secuencia de ADN , Ácido alfa-Linolénico/genética , Ácido alfa-Linolénico/metabolismoRESUMEN
The biochemical pathways involved in the biosynthesis and accumulation of storage lipids in seeds have been extensively studied. However, the regulatory mechanisms of those pathways, their environmental interactions and the ecological implications of variation are poorly understood. We have initiated a new approach: the analysis of natural variation in Arabidopsis thaliana. Three hundred and sixty accessions were surveyed for content of oil, very long chain fatty acids (VLCFAs) and polyunsaturated fatty acids (PUFAs) in their seeds. The results revealed extensive natural variation. A core set of accessions, the seeds of which reproducibly contain extreme amounts of oil, VLCFAs and PUFAs have been identified. Reproducible oil content ranged from 34.6 to 46.0% of seed dry weight. VLCFA content ranged from 13.0 to 21.2% of total fatty acids. PUFA content, ranged from 53.3 to 66.1% of total fatty acids. Interactions were also identified for PUFA and VLCFA content of seeds with vernalisation of plants. Mapping of the regions of the genome involved in controlling the traits was conducted in an F(2) population and indicated that natural variation at the loci FAE1 and FAD3 might be involved in the regulation of VLCFA and PUFA content, respectively. A set of accessions, which capture a broad range of the natural variation for these traits available in A. thaliana, has been selected to form a core set which can be used to further dissect the genetics of the regulation of seed lipid traits and to identify the genes involved.