Acyl-CoA elongase expression during seed development in Brassica napus.
The Bn-FAE1.1 and Bn-FAE1.2 genes encode the 3-ketoacyl-CoA synthase, a component of the elongation complex responsible for the synthesis of very long chain monounsaturated fatty acids (VLCMFA) in the seeds of Brassica napus. Bn-FAE1 gene expression was studied during seed development using two different cultivars: Gaspard, a high erucic acid rapeseed (HEAR), and ISLR4, a low erucic acid rapeseed (LEAR). The mRNA developmental profiles were similar for the two cultivars, the maximal expression levels being measured at 8 weeks after pollination (WAP) in HEAR and at 9 WAP in LEAR. Differential expression of Bn-FAE1.1 and Bn-FAE1.2 genes was also studied. In each cultivar the same expression profile was observed for both genes, but Bn-FAE1.2 was expressed at a lower level than Bn-FAE1.1. Secondly, VLCMFA synthesis was measured using particulate fractions prepared from maturating seeds harvested weekly after pollination. The oleoyl-CoA and ATP-dependent elongase activities increased from the 4th WAP in HEAR and reached the maximal level at 8 WAP, whereas both activities were absent in LEAR. In contrast, the 3-hydroxy dehydratase, a subunit of the elongase complex, had a similar activity in both cultivars and reached a maximum from 7 to 9 WAP. Finally, antibodies against the 3-ketoacyl-CoA synthase revealed a protein of 57 kDa present only in HEAR. Our results show: (i) that both genes are transcribed in HEAR and LEAR cultivars; (ii) that they are coordinately regulated; (iii) that Bn-FAE1.1 is quantitatively the major isoform expressed in seeds; (iv) that the Bn-FAE1 gene encodes a protein of 57 kDa responsible for the 3-ketoacyl-CoA synthase activity.
Puyaubert
J
J
Laboratoire de Biogenèse Membranaire, CNRS UMR 5544, Université V. Segalen Bordeaux 2, Bordeaux Cedex, France.
Garbay
B
B
Costaglioli
P
P
Dieryck
W
W
Roscoe
T J
TJ
Renard
M
M
Cassagne
C
C
Lessire
R
R
D000123:Acetyltransferases / Q000096:biosynthesis* / Q000235:genetics; D001937:Brassica / Q000196:embryology / Q000201:enzymology* / Q000235:genetics; D004746:Enoyl-CoA Hydratase / Q000378:metabolism; D000081031:Fatty Acid Elongases; D015971:Gene Expression Regulation, Enzymologic; D017343:Genes, Plant; D012333:RNA, Messenger / Q000096:biosynthesis; D012639:Seeds / Q000201:enzymology / Q000254:growth & development
D012333:RNA, Messenger; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases; D004746:Enoyl-CoA Hydratase