The GmFAD7 gene family from soybean: identification of novel genes and tissue-specific conformations of the FAD7 enzyme involved in desaturase activity

Abstract

The FAD7 gene encodes a ω3 fatty acid desaturase which catalyses the production of trienoic fatty acids (TAs) in plant chloroplasts. A novel GmFAD7 gene (named GmFAD7-2) has been identified in soybean, with high homology to the previously annotated GmFAD7 gene. Genomic sequencing analysis together with searches at the soybean genome database further confirmed that both GmFAD7 genes were located in two different loci within the soybean genome, suggesting that the soybean ω3 plastidial desaturase FAD7 is encoded by two different paralogous genes. Both GmFAD7-1 and GmFAD7-2 genes were expressed in all soybean tissues examined, displaying their highest mRNA accumulation in leaves. This expression profile contrasted with GmFAD3A and GmFAD3B mRNA accumulation, which was very low in this tissue. These results suggested a concerted control of plastidial and reticular ω3 desaturase gene expression in soybean mature leaves. Analysis of GmFAD7 protein distribution in different soybean tissues showed that, in mature leaves, two bands were detected, coincident with the higher expression level of both GmFAD7 genes and the highest 18:3 fatty acid accumulation. By contrast, in seeds, where FAD7 activity is low, specific GmFAD7 protein conformations were observed. These GmFAD7 protein conformations were affected in vitro by changes in the redox conditions of thiol groups and iron availability. These results suggest the existence of tissue-specific post-translational regulatory mechanisms affecting the distribution and conformation of the FAD7 enzymes related with the control of its activity.

Devolopmental and growth temperature regulation of omega-3 fatty acid desaturase genes in safflower (Carthamus tinctorius L.)

“…One difference between safflower and other LNA plant species was that 18:1 was not present in these tissues. The highest amount of trienoic fatty acids (i.e., LNA, 18:3) was observed in the leaves, representing more than 60% of total fatty acids, which was similar to other LNA plants (Andreu et al, 2010). In flowers, the LNA level was more than 30%, while LNA was not detected at all in developing seeds.…”

Genome-Wide Analysis of Fatty Acid Desaturases in Soybean (Glycine max)

“…However, there still existed some differences. Both GmFAD7 paralogous genes (GmFAD7-1 and GmFAD7-2) have been functionally characterized and expressed in all soybean tissues analyzed (Andreu et al 2010), whereas in Arabidopsis no AtFAD7 mRNA was detected in roots (Yadav et al 1993;Nishiuchi et al 1997).…”

“…High levels of GmFAB2C (Glyma14g27990) transcripts were expressed only in developing seeds, and mutations in this gene from two soybean germplasm sources, mutants A6 (30% stearate) and FAM94-41 (9% stearate), resulted in elevated seed stearic acid . Two FAD7 paralogous genes have been identified in soybean, GmFAD7-1 (Glyma18g43210) and GmFAD7-2 (Glyma07g18350; Andreu et al 2010). Both GmFAD7-1 and GmFAD7-2 genes were expressed in all soybean tissues examined, displaying their highest mRNA accumulation in leaves.…”

Non-redundant Contribution of the Plastidial FAD8 ω-3 Desaturase to Glycerolipid Unsaturation at Different Temperatures in Arabidopsis

“…In Arabidopsis, a single gene encodes for each of these enzymes (Yadav et al, 1993;Gibson et al, 1994). More recently, two different genes encoding isoforms of FAD7 (GmFAD7-1 and and FAD8 (GmFAD8-1 and GmFAD8-2) enzymes have been reported in soybean (Andreu et al, 2010;Román et al, 2012), being the only case in which isoforms have been identified for both plastidial -3 desaturases. More recently, two different genes encoding isoforms of FAD7 (GmFAD7-1 and and FAD8 (GmFAD8-1 and GmFAD8-2) enzymes have been reported in soybean (Andreu et al, 2010;Román et al, 2012), being the only case in which isoforms have been identified for both plastidial -3 desaturases.…”

“…In other plant species, like soybean (Glycine max) or flax (Linum usitatissimum), several isoforms of FAD3 have been detected (Bilyeu et al, 2003;Vrinten et al, 2005). Interestingly, the expression profiles of these genes showed differences in response to plant development, temperature or wounding, suggesting a high degree of specialization between isoforms in soybean (Andreu et al, 2010;Román et al, 2012;Lagunas et al, 2013). Interestingly, the expression profiles of these genes showed differences in response to plant development, temperature or wounding, suggesting a high degree of specialization between isoforms in soybean (Andreu et al, 2010;Román et al, 2012;Lagunas et al, 2013).…”