Sunflower WRINKLED1 Plays a Key Role in Transcriptional Regulation of Oil Biosynthesis

Abstract

Sunflower (Helianthus annuus) is one of the most important oilseed crops worldwide. However, the transcriptional regulation underlying oil accumulation in sunflower is not fully understood. WRINKLED1 (WRI1) is an essential transcription factor governing oil accumulation in plant cells. Here, we identify and characterize a sunflower ortholog of WRI1 (HaWRI1), which is highly expressed in developing seeds. Transient production of HaWRI1 stimulated substantial oil accumulation in Nicotiana benthamiana leaves. Dual-luciferase reporter assay, electrophoretic mobility shift assay, fatty acid quantification, and gene expression analysis demonstrate that HaWRI1 acts as a pivotal transcription factor controlling the expression of genes involved in late glycolysis and fatty acid biosynthesis. HaWRI1 directly binds to the cis-element, AW-box, in the promoter of biotin carboxyl carrier protein isoform 2 (BCCP2). In addition, we characterize an 80 amino-acid C-terminal domain of HaWRI1 that is crucial for transactivation. Moreover, seed-specific overexpression of HaWRI1 in Arabidopsis plants leads to enhanced seed oil content as well as upregulation of the genes involved in fatty acid biosynthesis. Taken together, our work demonstrates that HaWRI1 plays a pivotal role in the transcriptional control of seed oil accumulation, providing a potential target for bioengineering sunflower oil yield improvement.

Molecular basis of the key regulator WRINKLED1 in plant oil biosynthesis

“…Consistent with this notion, AtWRI1 orthologs have been identified in various plant species, both monocots and dicots, such as Brassica napus, Brachypodium distachyon, Camelina sativa, Glycine max, Elaeis guineensis, Helianthus annuus, and Zea mays (11,(19)(20)(21)(22)(23)(24)(25)(26). Transgenic plants overexpressing AtWRI1 or WRI1 orthologs exhibit elevated seed oil accumulation (4,9,11,19,24,26,27). In addition, ectopic expression of AtWRI1 or WRI1 orthologs leads to increased oil accumulation in leaves of stable transgenic plants or tobacco plants (via transient expression) (24,(28)(29)(30)(31)(32)(33).…”

“…WRI1 is therefore considered a key regulator in the transcriptional control of plant oil production (1,10). Consistent with this notion, AtWRI1 orthologs have been identified in various plant species, both monocots and dicots, such as Brassica napus, Brachypodium distachyon, Camelina sativa, Glycine max, Elaeis guineensis, Helianthus annuus, and Zea mays (11,(19)(20)(21)(22)(23)(24)(25)(26). Transgenic plants overexpressing AtWRI1 or WRI1 orthologs exhibit elevated seed oil accumulation (4,9,11,19,24,26,27).…”

WRINKLED1 Positively Regulates Oil Biosynthesis in Carya cathayensis

“…CcWRI1A/B were preferentially expressed in the developing embryo (Figure 2C,D), which is similar to those of AtWRI1, GmWRI1s, and HaWRI1. 2,7,20 Previous studies have shown that GmWRI1A and GmWRI1B were both nucleus-located, while only GmWRI1A but not GmWRI1B can transactivate targeted genes, suggesting that GmWRI1A and GmWRI1B are likely to regulate downstream genes in different ways. 20 It was also found that ZmWRI1B was developing into a housekeeping gene to maintain the TAG biosynthesis involved in different cellular processes; nonetheless, ZmWRI1A still mainly contributed to promoting FA biosynthesis during grain filling.…”

“…It is the major source of carbon and energy for seed germination and seedling establishment. It is also applied as a major calorie source for human nutrition and plays a critical role in industrial manufacturing. , …”

“…Recently, Gao et al resolved the crystal structure of the AtWRI1 protein and its recognized double-stranded DNA revealed how AtWRI1 binds to the AW-box and proposed a new idea by structurally modifying WRI1 to increase oil production in plant seeds . Notably, WRI1 orthologs from other various monocot and dicot plant species have also been identified, including Brachypodium distachyon, Elaeis guineensis, Glycine max, Jatropha curcas, Ricinus communis, Brassica napus, , Zea mays, , and Helianthus annuus . Homologous or heterologous expression of these WRI1 orthologs increased the oil content in seeds and vegetative tissues.…”