Enhancing microRNA167A expression in seed decreases the α‐linolenic acid content and increases seed size in Camelina sativa

Abstract

These authors contributed equally to this work. SUMMARYDespite 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 a-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 a-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.

Into the Seed: Auxin Controls Seed Development and Grain Yield

“…Indeed, recent studies have shown that some auxin signaling components or genes regulated by the auxin signaling pathway can alter seed size and/or seed weight. For instance, ARF6 and ARF8, which are partially controlled by microR167, appear to be required for seed size in Camelina [98]. Big Grain 1 (BG1), which is a plasma membrane-associated protein involved in auxin transport and the auxin response, has the potential to improve both grain size and weight in rice [99].…”

Genome-wide identification and functional characterization of the Camelina sativa WRKY gene family in response to abiotic stress

“…Numerous studies have focused on camelina seed yields and oil quality [8,9]. For example, the over-expression of micro-RNA167A in C. sativa seeds reduced the α-linolenic acid content and increased the seed size [10]. The expression of diacylglycerol acyltransferase 1 and glycerol-3phosphate dehydrogenase increased the seed oil yields in C. sativa [11].…”

OsmiR167a‐targeted auxin response factors modulate tiller angle via fine‐tuning auxin distribution in rice

“…MiR167 targeted the transcription factor ARF genes had been reported to be conserved among other plant species, including rice (Liu et al, 2012a), soybean (Wang et al, 2015), tomato (Liu et al, 2014), Ipomoea nil (Glazinska et al, 2014), Camelina sativa (Na et al, 2019) and so on. A total of 25 putative OsARFs have been identified in of rice (Guilfoyle and Hagen, 2007;Li et al, 2016;Wang et al, 2007).…”