Enhancing microRNA167A expression in seed decreases the α‐linolenic acid content and increases seed size in Camelina sativa. (14th February 2019)

• Record Type: Journal Article
• Authors: Na, GunNam; Mu, Xiaopeng; Grabowski, Paul; Schmutz, Jeremy; Lu, Chaofu
• Is Part Of: Plant journal. Volume 98:Number 2(2019)
• Page Start: 346
• Page End: 358
• Publication Date: 2019-02-14
• Subjects: microRNA167 -- transcription factors -- Camelina sativa -- fatty acid desaturase 3 -- α‐linolenic acid -- seed size; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.14223
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: Despite well established roles of microRNAs in plant development, few aspects have been addressed to understand their effects in seeds especially on lipid metabolism. In this study, we showed that overexpressing microRNA167A (miR167OE) in camelina ( Camelina sativa ) under a seed‐specific promoter changed fatty acid composition and increased seed size. Specifically, the miR167OE seeds had a lower α‐linolenic acid with a concomitantly higher linoleic acid content than the wild‐type. This decreased level of fatty acid desaturation corresponded to a decreased transcriptional expression of the camelina fatty acid desaturase3 ( CsFAD3 ) in developing seeds. MiR167 targeted the transcription factor auxin response factor (CsARF8) in camelina, as had been reported previously in Arabidopsis. Chromatin immunoprecipitation experiments combined with transcriptome analysis indicated that CsARF8 bound to promoters of camelina bZIP67 and ABI3 genes. These transcription factors directly or through the ABI3‐bZIP12 pathway regulate CsFAD3 expression and affect α‐linolenic acid accumulation. In addition, to decipher the miR167A‐CsARF8 mediated transcriptional cascade for CsFAD3 suppression, transcriptome analysis was conducted to implicate mechanisms that regulate seed size in camelina. Expression levels of many genes were altered in miR167OE, including orthologs that have previously been identified to affect seed size in other plants. Most notably, genes for seed coat development such as suberin and lignin biosynthesis were down‐regulated. This study provides valuable insights into the regulatory mechanism of fatty acid metabolism and seed size determination, and suggests possible approaches to improve these important traits in camelina. Significance Statement: The fatty acid composition of oil and seed size are among the most important traits of oilseeds. Overexpression of a microRNA, the key post‐transcriptional regulator, caused decreased α‐linolenic acid content and increased seed size in the oilseed crop Camelina sativa, and provided a powerful tool for deciphering regulatory mechanisms that affect fatty acid biosynthesis and seed development.