Abstract
BackgroundIn the oilseed crop Brassica napus (rapeseed), various metabolic processes influence seed oil content, oil quality, and biological yield. However, the role of plastid membrane proteins in these traits has not been explored.ResultsOur genome-wide association study (GWAS) of 520 B. napus accessions identified the chloroplast membrane protein-localized FATTY ACID EXPORTER 1-1 (FAX1-1) as a candidate associated with biological yield. Seed transcript levels of BnaFAX1-1 were higher in a cultivar with high seed oil content relative to a low-oil cultivar. BnaFAX1-1 was localized to the plastid envelope. When expressed in Arabidopsis thaliana, BnaFAX1-1 enhanced biological yield (total plant dry matter), seed yield and seed oil content per plant. Likewise, in the field, B. napus BnaFAX1-1 overexpression lines (BnaFAX1-1-OE) displayed significantly enhanced biological yield, seed yield, and seed oil content compared with the wild type. BnaFAX1-1 overexpression also up-regulated gibberellic acid 4 (GA4) biosynthesis, which may contribute to biological yield improvement. Furthermore, oleic acid (C18:1) significantly increased in BnaFAX1-1 overexpression seeds.ConclusionOur results indicated that the putative fatty acid exporter BnaFAX1-1 may simultaneously improve seed oil content, oil quality and biological yield in B. napus, providing new approaches for future molecular breeding.
Highlights
Brassica napus is an important oilseed crop for edible oils, as the oil extracted from its seeds is richPrevious studies revealed that rapeseed seed oil production may be enhanced by overexpressing enzymes or transcription factors involved in various metabolicXiao et al Biotechnol Biofuels (2021) 14:190 processes
To determine the contribution of chloroplast envelope proteins to biological yield, which might increase seed oil production in B. napus, we identified genes encoding proteins predicted to localize to the chloroplast envelope that mapped near significant single-nucleotide polymorphisms (SNPs) from our previous genome-wide association study (GWAS) results in B. napus
Identification of chloroplast membrane‐localized proteins potentially contributing to biological yield in B. napus We previously detected SNPs that are significantly associated with biological yield during a GWAS of 520 B. napus accessions [30]
Summary
Identification of chloroplast membrane‐localized proteins potentially contributing to biological yield in B. napus We previously detected SNPs that are significantly associated with biological yield during a GWAS of 520 B. napus accessions [30]. We determined the total lipid content of mature seeds, which indicated that overexpression lines accumulated more total lipid content relative to the WT (Fig. 3D) These results indicated that the heterologous overexpression of BnaFAX1-1 in Arabidopsis promoted plant growth and development, and led to an increase in seed oil production. Gibberellin and leaf lipid contents in B. napus plants overexpressing BnaFAX1‐1 To test the effect of BnaFAX1-1 overexpression in B. napus on biomass accumulation, we analyzed the growth kinetics of three independent BnaFAX1-1 overexpression lines selected at random (OE#17, OE#19 and OE#21) (Fig. 4A). We observed a higher lipid content for phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in the leaves of OE#19 and OE#21 plants when compared to WT (Fig. 6) These results revealed that BnaFAX1-1 share the same role as AtFAX1 when ectopically expressed in leaves for the regulation of leaf lipid and biomass accumulation. These results, revealed that BnaFAX1-1 may have important application value in B. napus molecular breeding to improve seed oil content, oil quality, seed yield and biological yield
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