Native promoter-mediated transcriptional regulation of crucial oleosin protein OLE1 from Prunus sibirica for seed development and high oil accumulation.

Oleosin (OLE) is vital to stabilize lipid droplet for seed triacylglycerol (TAG) storage. This work aimed to determine key OLE and to unravel mechanism that governed seed oil accumulation of Prunus sibirica for developing biodiesel. An integrated assay of global identification of LD-related protein and the cross-accessions/developing stages comparisons associated with oil accumulative amount and OLE transcript level was performed on seeds of 12 plus trees of P. sibirica to identify OLE1 (15.5 kDa) as key oleosin protein crucial for high seed oil accumulation. The OLE1 gene and its promoter were cloned from P. sibirica seeds, and overexpression of PsOLE1 in Arabidopsis was conducted under the controls of native promoter and constitutive CaMV35S promoter, respectively. PsOLE1 promoter had seed-specific cis-elements and showed seed specificity, by which PsOLE1 was specifically expressed in seeds. Ectopic overexpression of PsOLE1, especially driven by its promoter, could facilitate seed development and oil accumulation with an increase in unsaturated FAs, and upregulate transcript of TAG assembly enzymes, but suppress transcript of LD/TAG-hydrolyzed lipases and transporters, revealing a role of native promoter-mediated transcription of PsOLE1 in seed development and oil accumulation. PsOLE1 and its promoter have considerable potential for engineering oil accumulation in oilseed plants.

Determination of superior Pistacia chinensis accession with high-quality seed oil and biodiesel production and revelation of LEC1/WRI1-mediated high oil accumulative mechanism for better developing woody biodiesel.

BACKGROUND: Based on our previous studied on different provenances of Pistacia chinensis, some accessions with high quality and quantity of seed oils has emerged as novel source of biodiesel. To better develop P. chinensis seed oils as woody biodiesel, a concurrent exploration of oil content, FA profile, biodiesel yield, and fuel properties was conducted on the seeds from 5 plus germplasms to determine superior genotype for ideal biodiesel production. Another vital challenge is to unravel mechanism that govern the differences in oil content and FA profile of P. chinensis seeds across different accessions. FA biosynthesis and oil accumulation of oil plants are known to be highly controlled by the transcription factors. An integrated analysis of our recent transcriptome data, qRT-PCR detection and functional identification was performed as an attempt to highlight LEC1/WRI1-mediated transcription regulatory mechanism for high-quality oil accumulation in P. chinensis seeds. RESULTS: To select ideal germplasm and unravel high oil accumulative mechanism for developing P. chinensis seed oils as biodiesel, five plus trees (accession PC-BJ/PC-AH/PC-SX/PC-HN/PC-HB) with high-yield seeds were selected to assess the variabilities in weight, oil content, FA profile, biodiesel yield and fuel property, revealing a variation in the levels of seed oil (50.76-60.88%), monounsaturated FA (42.80-70.72%) and polyunsaturated FA (18.78-43.35%), and biodiesel yield (84.98-98.15%) across different accessions. PC-HN had a maximum values of seed weight (26.23 mg), oil (60.88%) and biodiesel yield (98.15%), and ideal proportions of C18:1 (69.94%), C18:2 (17.65%) and C18:3 (1.13%), implying that seed oils of accession PC-HN was the most suitable for ideal biodiesel production. To highlight molecular mechanism that govern such differences in oil content and FA profile of different accessions, a combination of our recent transcriptome data, qRT-PCR detection and protein interaction analysis was performed to identify a pivotal role of LEC1/WRI1-mediated transcription regulatory network in high oil accumulation of P. chinensis seeds from different accessions. Notably, overexpression of PcWRI1 or PcLEC1 from P. chinensis seeds in Arabidopsis could facilitate seed development and upregulate several genes relevant for carbon flux allocation (plastidic glycolysis and acetyl-CoA generation), FA synthesis, TAG assembly and oil storage, causing an increase in seed oil content and monounsaturated FA level, destined for biodiesel fuel property improvement. Our findings may present strategies for better developing P. chinensis seed oils as biodiesel feedstock and bioengineering its high oil accumulation. CONCLUSIONS: This is the first report on the cross-accessions assessments of P. chinensis seed oils to determine ideal accession for high-quality biodiesel production, and an effective combination of PcWRI1 or PcLEC1 overexpression, morphological assay, oil accumulation and qRT-PCR detection was applied to unravel a role of LEC1/WRI1-mediated regulatory network for oil accumulation in P. chinensis seeds, and to highlight the potential application of PcWRI1 or PcLEC1 for increasing oil production. Our finding may provide new strategies for developing biodiesel resource and molecular breeding.