WRINKLED1 (WRI1), an APETALA2 (AP2)-type transcription factor, has been shown to be required for the regulation of carbon partitioning into fatty acid (FA) synthesis in plant seeds. To our knowledge, the regulatory network of WRI1 remains unknown in Prunus sibirica kernel (PSK), a novel woody biodiesel feedstock in China. In this study, based on the transcriptional data from developing oilseeds of multiple plant species, we identified 161 WRI1 -coexpressed genes using weighted gene co-expression network analysis (WGCNA). The major portion of WRI1 -coexpressed genes was characterized to be involved in carbon partitioning and FA biosynthesis. Additionally, we detected the temporal patterns for oil content and FA compositions in developing PSK from two different germplasms (AS-85 and AS-86). The major differences between the two germplasms are higher contents of oil and C18:1 in AS-85 than in AS-86 at a mature stage. Thus, AS-85 and AS-86 are desirable materials to explore the molecular and metabolic mechanisms of oil accumulation in Siberian apricot. Expression analysis in developing PSK of AS-85 and AS-86 indicated that the expression level of P . sibirica WRI1 (PsWRI1) was closely correlated to accumulative rate of oil. Also, the comparison of expression profiles in developing PSK of AS-85 and AS-86 displayed that the pPK , E1-α , E2 , TAL , BC , MCMT , BS , SAD and FAD2 have a high correlation with PsWRI1 . Transient expression showed that Pro SAD - and Pro BS -driving GUS expression showed no substantial difference between AS-85 and AS-86, while the expression level of Pro PEPCK -AS-85 driving GUS was significantly higher than that of Pro PEPCK -AS-86 driving GUS. Additionally, transient co-transformation with PsWRI1 revealed that Pro SAD , Pro PEPCK and Pro BS activity could be specifically up-regulated by PsWRI1. This regulatory mechanism of PsWRI1 may create a steep concentration difference, thereby facilitating carbon flux into C18:1 accumulation in developing PSK. Overall, all our findings imply a versatile mechanism of WRI1 to optimize carbon allocation for oil accumulation, which can provide reference for researching the woody biodiesel plants.

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Background Vernonia amygdalina as a tropical horticultural crop has been widely used for medicinal herb, feed, and vegetable. Recently, increasing studies revealed that this species possesses multiple pharmacological properties. Notably, V. amygdalina leaves possess an abundance of flavonoids, but the specific profiles of flavonoids and the mechanisms of fl avonoid bi osynthesis in developing leaves are largely unknown. Methods The total flavonoids of V. amygdalina leaves were detected using ultraviolet spectrophotometer. The temporal flavonoid profiles of V. amygdalina leaves were analyzed by LC-MS. The transcriptome analysis of V. amygdalina leaves was performed by Illumina sequencing. Functional annotation and differential expression analysis of V. amygdalina genes were performed by Blast2GO v2.3.5 and RSEM v1.2.31, respectively. qRT-PCR analysis was used to verify the gene expressions in developing V. amygdalina leaves. Results By LC-MS analysis, three substrates (p-coumaric acid, trans-cinnamic acid, and phenylalanine) for flavonoid biosynthesis were identified in V. amygdalina leaves. Additionally, 42 flavonoids were identified from V. amygdalina leaves, including six dihydroflavones, 14 flavones, eight isoflavones, nine flavonols, two xanthones, one chalcone, one cyanidin, and one dihydroflavonol. Glycosylation and methylation were common at the hydroxy group of C3, C7, and C4’ positions. Moreover, dynamic patterns of different flavonoids showed diversity. By Illumina sequencing, the obtained over 200 million valid reads were assembled into 60,422 genes. Blast analysis indicated that 31,872 genes were annotated at least in one of public databases. Greatly increasing molecular resources makes up for the lack of gene information in V. amygdalina. By digital expression profiling and qRT-PCR, we specifically characterized some key enzymes, such as Va-PAL1, Va-PAL4, Va-C4H1, Va-4CL3, Va-ACC1, Va-CHS1, Va-CHI, Va-FNSII, and Va-IFS3, involved in flavonoid biosynthesis. Importantly, integrated metabolome and transcriptome data of V. amygdalina leaves, we systematically constructed a flavonoid biosynthetic pathway with regards to material supplying, flavonoid scaffold biosynthesis, and flavonoid modifications. Our findings contribute significantly to understand the underlying mechanisms of flavonoid biosynthesis in V. amygdalina leaves, and also provide valuable information for potential metabolic engineering.

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Siberian apricot seed kernel (SASK) contains a high of 50% oil with suitable fuel properties conformed to biodiesel standard. To date, Prunus sibirica is a novel non‐crop feedstock for biodiesel production in China. Here, oil contents and fatty acid (FA) compositions were identified in developing SASK from AS‐80 and AS‐84, at intervals of 1 week from 3 weeks after anthesis (WAA) to 9 weeks. The major differences in oil content between C18:1 and C18:2 levels were greater among the AS‐80 (32.69/15.48 g/100 g) than among the AS‐84 (25.78/13.15 g/100 g). Subsequently, the SASKs from 4, 6, and 8 WAA, respectively, representing early, middle, and late phases of oil accumulation, were selected as optimal samples for lipidomics analysis. It was notable that 18:1/18:1/18:2, 18:1/18:1/18:3, and 18:2/18:2/18:2 were the prominent compositions in triacylglycerol (TAG), and their higher content found among the AS‐80 was consistent with FA results. Although phosphatidic acid (PA) is directly connected with diacylglycerol (DAG) in Kennedy pathway, we found significant difference between PA and DAG compositions. The resulting molecular species differ in acyl composition depending on whether they were generated via phosphatidylcholine (PC) or Kennedy pathway. By qRT‐PCR analysis, the expression levels of FAD3, PDCT, and DAG‐CPT related to the biosynthesis of polyunsaturated fatty acids (PUFAs) showed a gradual decrease with SASK mature, explaining the drastic change of DAG‐18:3/18:3 content. Additionally, the lipidomics data coupled with qRT‐PCR analysis suggested that phospholipid:DAG acyltransferase may play a critical role in incorporation of PUFAs into sn‐3 of TAG. Our data contribute significantly to understand the underlying mechanisms of lipid accumulation in P. sibirica, and may also present strategies for engineering oil accumulation in oilseed plants.