The molecular mechanism of WRINKLED1 transcription factor regulating oil accumulation in developing seeds of castor bean

The transcription factor WRINKLED1(WRI1),a member of AP2 gene family that contain typical AP2 domains,has been considered as a master regulator regulating oil biosynthesis in oilseeds.However,the regulatory mechanism of RcWRI1 in regulating oil accumulation during seed development has not been clearly addressed.Castor bean(Ricinus communis)is one of the most important non-edible oil crops and its seed oils are rich in hydroxy fatty acids,widely applied in industry.In this study,based on castor bean reference genome,three RcWRIs genes(RcWRI1,RcWRI2 and RcWRI3)were identified and the expressed association of RcWRI1 with oil accumulation were determined.Heterologous transformation of RcWRI1 significantly increased oil content in tobacco leaf,confirming that RcWRI1 activate lipid biosynthesis pathway.Using DNA Affinity Purification sequencing(DAP-seq)technology,we confirmed RcWRI1 binding with Transcription Start Site of genes and identified 7961 WRI1-binding candidate genes.Functionally,these identified genes were mainly involved in diverse metabolism pathways(including lipid biosynthesis).Three cis-elements AW-box([CnTnG](n)7[CG])and AW-boxes like([GnAnC](n)6[GC]/[GnAnC](n)7[G])bound with RcWRI1 were identified.Co-expression network analysis of RcWRI1 further found that RcWRI1 might be widely involved in biosynthesis of storage materials during seed development.In particular,yeast one hybrid experiments found that both AP2 domains within RcWRI1 were required in binding targeted genes.These results not only provide new evidence to understand the regulatory mechanism of RcWRI1 in regulation of oil accumulation during castor bean seed development,but also give candidate gene resource for subsequent genetic improvement toward increasing oil content in oilseed crops.

Effects of Heat Stress during Seed Filling Stage on Brassica napus Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise,the threat of heat stress to rapeseed production is becoming more obvious.Exploring the response characteristics of two important biological pathways,oil accumulation and photosynthesis,to heat stress during B.napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed.The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B.napus germplasms with different oil content and environmental sensitivity,including 6 rapeseed varieties which exhibited environmentsensitive/insensitive and with high,medium or low oil content,were tested by whole plant heat stress or the in vitro silique culture system.Both assay exhibited similar trend on oil content of the rapeseed germplasms.The heat effect on the chlorophyll fluorescence kinetic parameters F_(v)/F_(m),ETR and Y(Ⅱ)were also consistent.Heat stress significantly decreased oil content,although there was abundant genetic variation on heat tolerance among the genotypes.Correlation analysis showed that the decrease rate of F_(v)/F_(m) of silique heat-stressed B.napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed(R=0.9214,P-value<0.01).Overall,the results indicated that heat stress inhibited oil accumulation and photosynthesis in B.napus developing seed.The decrease rate of chlorophyll fluorescence parameter F_(v)/F_(m) of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification.Further,two heat insensitive rapeseed varieties with high oil content were identified.

Antagonistic MADS-box transcription factors SEEDSTICK and SEPALLATA3 form a transcriptional regulatory network that regulates seed oil accumulation

Transcriptional regulation is essential for balancing multiple metabolic pathways that influence oil accumulation in seeds.Thus far,the transcriptional regulatory mechanisms that govern seed oil accumulation remain largely unknown.Here,we identified the transcriptional regulatory network composed of MADS-box transcription factors SEEDSTICK(STK)and SEPALLATA3(SEP3),which bridges several key genes to regulate oil accumulation in seeds.We found that STK,highly expressed in the developing embryo,positively regulates seed oil accumulation in Arabidopsis(Arabidopsis thaliana).Furthermore,we discovered that SEP3 physically interacts with STK in vivo and in vitro.Seed oil content is increased by the SEP3 mutation,while it is decreased by SEP3 overexpression.The chromatin immunoprecipitation,electrophoretic mobility shift assay,and transient dual-luciferase reporter assays showed that STK positively regulates seed oil accumulation by directly repressing the expression of MYB5,SEP3,and SEED FATTY ACID REDUCER 4(SFAR4).Moreover,genetic and molecular analyses demonstrated that STK and SEP3 antagonistically regulate seed oil production and that SEP3 weakens the binding ability of STK to MYB5,SEP3,and SFAR4.Additionally,we demonstrated that TRANSPARENT TESTA 8(TT8)and ACYL-ACYL CARRIER PROTEIN DESATURASE 3(AAD3)are direct targets of MYB5 during seed oil accumulation in Arabidopsis.Together,our findings provide the transcriptional regulatory network antagonistically orchestrated by STK and SEP3,which fine tunes oil accumulation in seeds.

Quantitative prediction model for the depth limit of oil accumulation in the deep carbonate rocks:A case study of Lower Ordovician in Tazhong area of Tarim Basin

With continuous hydrocarbon exploration extending to deeper basins,the deepest industrial oil accumulation was discovered below 8,200 m,revealing a new exploration field.Hence,the extent to which oil exploration can be extended,and the prediction of the depth limit of oil accumulation(DLOA),are issues that have attracted significant attention in petroleum geology.Since it is difficult to characterize the evolution of the physical properties of the marine carbonate reservoir with burial depth,and the deepest drilling still cannot reach the DLOA.Hence,the DLOA cannot be predicted by directly establishing the relationship between the ratio of drilling to the dry layer and the depth.In this study,by establishing the relationships between the porosity and the depth and dry layer ratio of the carbonate reservoir,the relationships between the depth and dry layer ratio were obtained collectively.The depth corresponding to a dry layer ratio of 100%is the DLOA.Based on this,a quantitative prediction model for the DLOA was finally built.The results indicate that the porosity of the carbonate reservoir,Lower Ordovician in Tazhong area of Tarim Basin,tends to decrease with burial depth,and manifests as an overall low porosity reservoir in deep layer.The critical porosity of the DLOA was 1.8%,which is the critical geological condition corresponding to a 100%dry layer ratio encountered in the reservoir.The depth of the DLOA was 9,000 m.This study provides a new method for DLOA prediction that is beneficial for a deeper understanding of oil accumulation,and is of great importance for scientific guidance on deep oil drilling.

Source and accumulation process of Jurassic biodegraded oil in the Eastern Junggar Basin,NW China

Biodegradation usually obscures or even radically alters the original characteristics of oil biomarkers.The mixing of oil from multiple sources makes each source difficult to trace.Identifying the source of biodegraded oil from multiple sources has always been a hard nut to crack.Rising to this challenge,in this study-we carried out a comprehensive investigation of biodegradation impacts,oil-source correlation,and oil charging history to trace the source and reveal the mixing process of biodegraded oil in the Toutunhe Formation(J_(2)t)in the eastern Junggar Basin,NW China.The oil of this area was biodegraded to different extent,consequently,many commonly used biomarker parameters(e.g.Pr/Ph,Pr/n C_(17))became less powerful for oil-source correlation.To address this problem,the resistance of many biomarkers to biodegradation was analyzed,and those of high bio resistance were selected to generate a more reliable oil-source correlation.The results revealed that biodegraded oil was a mixture of oil sourced from Lucaogou Formation(P_(2)l)and Xiaoquangou Formation(T_(2-3)xq).Core sample observation,microscopic fluorescent analysis and fluid inclusion analysis were combined to analyze comprehensively oil charging history.The analysis of accumulation process exhibited that the existing oil in J_(2)t was a mixture originated from the P_(2)l and T_(2-3)xq source rocks in two separate charging stages when it underwent a complicated process of charging,biodegradation,recharging and mixing.

Oil and gas source and accumulation of Zhongqiu 1 trap in Qiulitage structural belt, Tarim Basin, NW China

Well Zhongqiu 1 obtained highly productive oil-gas stream in the footwall of Zhongqiu structure, marking the strategic breakthrough of Qiulitag structural belt in the Tarim Basin. However, the oil and gas sources in Zhongqiu structural belt and the reservoir formation process in Zhongqiu 1 trap remain unclear, so study on these issues may provide important basis for the next step of oil and gas exploration and deployment in Qiulitage structural belt. In this study, a systematic correlation of oil and gas source in Well Zhongqiu 1 has been carried out. The oil in Well Zhongqiu 1 is derived from Triassic lacustrine mudstone, while the gas is a typical coal-derived gas and mainly from Jurassic coal measures. The oil charging in Well Zhongqiu 1 mainly took place during the sedimentary period from Jidike Formation to Kangcun Formation in Neogene, and the oil was mainly contributed by Triassic source rock;large-scale natural gas charging occurred in the sedimentary period of Kuqa Formation in Neogene, and the coal-derived gas generated in the late Jurassic caused large-scale gas invasion to the early Triassic crude oil reservoirs. The Zhongqiu 1 trap was formed earlier than or at the same period as the hydrocarbon generation and expulsion period of Triassic-Jurassic source rocks. Active faults provided paths for hydrocarbon migration. The source rocks-faults-traps matched well in time and space. Traps in the footwall of the Zhongqiu structural fault have similar reservoir-forming conditions with the Zhongqiu 1 trap, so they are favorable targets in the next step of exploration.

A Study of the Accompanying Relationships between Uranium and Oil

It is not occasional that uranium deposits and oil accumulation occur in the same depression in the Erlian basin, Inner Mongolia. Some evidences show certain relations between uranium and oil in origin. This paper discusses and analyses the evidence for the relations between uranium deposits and oil and gas accumulation in terms of spatial distribution, geology, hydrochemistry and geochemistry. The paper also deals with the mechanism of the formation of uranium deposits and points out that it is of significance to use uranium as an indicator to search for oil and vice versa.

Evolution of Ordovician YJ1X ultra-deep oil reservoir in the Yuecan oilfield, Tarim Basin, NW China

Based on a combined in-situ calcite U-Pb dating, molecular geochemical correlations of reservoir oil and extract from reservoir rocks, and fluid inclusion analysis, the charge and evolution history of the YJ1X ultra-deep oil reservoir of the Ordovician Yijianfang Formation in the southwestern part of the Tabei Uplift has been determined systematically.(1) The reservoir oil, free oil and inclusion oil have similar geochemical characteristics and are presumably derived from marine source rock deposited in similar sedimentary environment.(2) The reservoir oil, free oil and inclusion oil have similar maturities with calculated equivalent vitrinite reflectance values in the range of 0.80%-0.96%.(3) Two types(Group Ⅰ and Ⅱ) of oil inclusion assemblages(OIAs) have been identified in the reservoir, of which Group Ⅰ represents the original gas-saturated oil entering the trap during the initial oil charge, whereas Group Ⅱ represents undersaturated residual oil retained in the reservoir after minor leakage of light hydrocarbon.(4) The reservoir experienced oil charge only once during the Early Devonian around 425 Ma and has been well preserved after the minor light hydrocarbon leakage in the Middle Devonian. The study shows that there may be old oil and gas accumulations in ultra-deep strata of petroliferous basins with well-developed caprock and stable tectonic background.

Differences and controlling factors of composite hydrocarbon accumulations in the Tazhong uplift, Tarim Basin, NW China

Based on three-dimensional seismic interpretation, structural and sedimentary feature analysis, and examination of fluid properties and production dynamics, the regularity and main controlling factors of hydrocarbon accumulation in the Tazhong uplift, Tarim Basin are investigated. The results show that the oil and gas in the Tazhong uplift has the characteristics of complex accumulation mainly controlled by faults, and more than 80% of the oil and gas reserves are enriched along fault zones. There are large thrust and strike-slip faults in the Tazhong uplift, and the coupling relationship between the formation and evolution of the faults and accumulation determine the difference in complex oil and gas accumulations. The active scale and stage of faults determine the fullness of the traps and the balance of the phase, that is, the blocking of the transport system, the insufficient filling of oil and gas, and the unsteady state of fluid accumulation are dependent on the faults. The multi-period tectonic sedimentary evolution controls the differences of trap conditions in the fault zones, and the multi-phase hydrocarbon migration and accumulation causes the differences of fluid distribution in the fault zones. The theory of differential oil and gas accumulation controlled by fault is the key to the overall evaluation, three-dimensional development and discovery of new reserves in the Tazhong uplift.

Petroleum exploration breakthrough and geological significance in Cretaceous Yingcheng and Denglouku formations of Shuangcheng area, northern Songliao Basin, NE China

Based on drilling geological,geochemical,geophysical and production test data,the characteristics of source rocks,reservoir rocks and caprocks,as well as the process of hydrocarbon generation,trap evolution and oil accumulation of the oil-bearing assemblage composed of the Cretaceous Yingcheng Formation(K1yc)and Denglouku Formation(K1d)in the Shuangcheng area,northern Songliao Basin,NE China,were analyzed by using the research methods for petroleum systems.The source rocks mainly exist in K1yc,with the organic matters mainly originated from lower aquatic organisms and algae,and reaching the grade of high-quality source rock in terms of organic abundance.The crude oil,which is characterized by low density,high freezing point and high wax content,is believed to have generated by the K1yc source rocks.The reservoir rocks include K1d sandstones and K1yc glutenites.The mudstone in the fourth member of K1d serves as the direct caprock of the oil reservoir.The oil was generated during the period between Yaojia Formation and Nenjiang Formation,and then accumulated during the periods of Nenjiang Formation and Paleogene–Neogene.The traps evolved in three stages:the late Yingcheng Formation,the late Quantou Formation and the late Nenjiang Formation,forming structural and structural-lithologic reservoirs.It is concluded that good source-reservoir-caprock assemblage,late hydrocarbon charging,short migration distance and stable tectonic setting are favorable factors for the formation of oil reservoirs.

Comparative transcriptome analysis on candidate genes involved in lipid biosynthesis of developing kernels for three walnut cultivars in Xinjiang

Walnut(Juglans regia L.)is a good source of lipids and polyunsaturated fatty acids(PUFAs).In order to explore the biosynthesis molecular mechanism of oil accumulation and fatty acid(FA)synthesis in walnut,the samples at different development periods of three walnut cultivars,’Zhipi’(ZP),’Xinwu 417’(W417)and’Xinwen 81’(W81)were collected for transcriptomic analysis.The analysis of oil accumulation and FA profiles showed that the oil content in mature walnut kernel was nearly 70%,and over 90%of FAs were PUFAs.We identified 126 candidate genes including 64 genes for FA de novo synthesis,45 genes for triacylglycerol assembly,and 17 genes for oil bodies involved in lipid biosynthesis by RNA-sequencing.Ten key enzymes including ACCase,LACS6,LACS8,SAD,FAD2,FAD3,LPAAT1,DGAT2,PDAT2,and PLC encoded by 19 genes were highly associated with lipid biosynthesis.Quantitative PCR analysis further validated 9 important genes,and the results were well consistent with our transcriptomic data.Finally,5 important transcription factors including WRI1,ABI3,FUS3,PKL and VAL1 were identified,and their main regulatory genes might contain ACCase,KASII,LACS,FAD3 and LPAAT which were determined through correlation analysis of expression levels for 27 walnut samples.These findings will provide a comprehensive understanding and valuable information on the genetic engineering and molecular breeding in walnut.

Enhanced production of seed oil with improved fatty acid composition by overexpressing NAD^(+)-dependent glycerol-3-phosphate dehydrogenase in soybean

There is growing interest in expanding the production of soybean oils(mainly triacylglycerol, or TAG) to meet rising feed demand and address global energy concerns. We report that a plastidlocalized glycerol-3-phosphate dehydrogenase(GPDH), encoded by GmGPDHp1 gene, catalyzes the formation of glycerol-3-phosphate(G3 P), an obligate substrate required for TAG biosynthesis.Overexpression of GmGPDHp1 increases soybean seed oil content with high levels of unsaturated fatty acids(FAs), especially oleic acid(C18:1), without detectably affecting growth or seed protein content or seed weight. Based on the lipidomic analyses, we found that the increase in G3 P content led to an elevated diacylglycerol(DAG) pool, in which the Kennedy pathwayderived DAG was mostly increased, followed by PC-derived DAG, thereby promoting the synthesis of TAG containing relatively high proportion of C18:1. The increased G3 P levels induced several transcriptional alterations of genes involved in the glycerolipid pathways. In particular, genes encoding the enzymes responsible for de novo glycerolipid synthesis were largely upregulated in the transgenic lines, in-line with the identified biochemical phenotype. These results reveal a key role for GmGPDHp1-mediated G3 P metabolism in enhancing TAG synthesis and demonstrate a strategy to modify the FA compositions of soybean oils for improved nutrition and biofuel.

Transcriptional regulation of oil biosynthesis inseed plants: Current understanding, applications,and perspectives

Plants produce and accumulate triacylglycerol(TAG)in their seeds as an energy reservoir to support the processes of seed germination and seedling development.Plant seed oils are vital not only for the human diet but also as renewable feedstocks for industrial use.TAG biosynthesis consists of two major steps:de novo fatty acid biosynthesis in the plastids and TAG assembly in the endoplasmic reticulum.The latest advances in unraveling transcriptional regulation have shed light on the molecular mechanisms of plant oil biosynthesis.We summarize recent progress in understanding the regulatory mechanisms of wellcharacterized and newly discovered transcription factors and other types of regulators that control plant fatty acid biosynthesis.The emerging picture shows that plant oil biosynthesis responds to developmental and environmental cues that stimulate a network of interacting transcriptional activators and repressors,which in turn fine-tune the spatiotemporal regulation of the pathway genes.

Reservoir formation conditions and key technologies for exploration and development in Qingcheng large oilfield

The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geological reserves of 358 million tons,predicted geological reserves of 693 million tons,and a total of 1.051 billion tons of shale oil resources.This achieves a historic breakthrough in exploration of shale oil in Chang 7 Member.In recent years,focusing on key issues,such as whether there develop sweet spots in source rock,whether commercial oil production capacity can be formed,and whether scale-effective development can be achieved,studies about geological conditions for shale oil accumulation have been continuously carried out,key supporting technologies have been developed,and a series of theoretical innovations and technological breakthroughs have been achieved in oil exploration in source rocks.The results indicate that shale oil accumulation in Chang 7 Member is controlled by following factors.Firstly,lacustrine black shale,dark mudstone and other high-quality source rocks lay a material foundation for shale oil formation.Secondly,sandy deposits intercalated within black shale and dark mudstones are exploration sweet spots,and sandbody combination types are controlled by morphology of bottom of the lacustrine basin.Thirdly,reservoir properties are good due to development of micro-nano pore throats.Finally,reservoirs with high oil saturation and high gas-oil ratio are formed due to high-intensity oil charging in source rock.Effective matching of multiple factors is a key for shale oil accumulation in Chang 7 Member in Ordos Basin.Through innovation of key supporting technologies,exploration and development technologies for shale oil are developed,and substantial breakthrough on exploration and development of shale oil is realized.The first application of logging-seismic combination technology in loess plateau improves significantly quality of 3D seismic data,which effectively guides prediction of sandy sweet spots.Three-quality well logging technology is used for further evaluation of geological and engineering sweet spots of shale oil.With volumetric fracturing technology based on precise segmentation of long horizontal wells,initial daily oil production of individual well is increased from previously 10 tons to more than 18 tons.The exploration breakthrough in source rocks in Chang 7 Member in Qingcheng oilfield provides an important resource base for the second accelerated development of Changqing Oilfield.It is predicated that oil production from shale in Chang 7 Member in Qingcheng oilfield will reach three million tons in 2022 and five million tons in 2025.

Reservoir accumulation conditions and key exploration&development technologies for Keshen gas field in Tarim Basin

The Keshen gas field is located in the central part of Kuqa foreland thrust belt in Tarim Basin,and is another large gas field discovered in Kuqa depression after Kela 2 gas field.Since the breakthrough in 2008,a number of large and medium scale gas reservoirs including Keshen 2,Keshen 5 and Keshen 8 have been discovered,that are characterized by ultra depth,ultra-high pressure,ultra-low porosity,ultra-low permeability,high temperature and high pressure.With natural gas geological reserves of nearly trillion cubic meters and production capacity of nearly 5.5 billion cubic meters,the Keshen gas field is the main natural gas producing area in Tarim Oilfield.The Keshen gas field is located in a series of thrusting imbrication structures in the Kelasu structural belt of Kuqa foreland thrust belt.The salt roof structure,plastic rheology of salt beds and pre-salt faulted anticlinal structure constitute the large wedge-shaped thrust body.The thick delta sandstone of the Cretaceous Bashijike Formation is widely distributed,and it forms the superior reservoir-caprock combination with overlying Paleogene thick gypsum-salt bed.The deep Jurassic-Triassic oil and gas migrate vertically along fault system formed in Late Himalaya,break through the thick Cretaceous mudstone and move laterally along the fracture system of the pre-salt reservoirs,to form anticline and fault anticline high pressure reservoir groups.Through near ten years of studies,the three-dimensional seismic acquisition and processing technology for complex mountainous areas,extrusion salt-related structural modeling technology and fractured low-porosity sandstone reservoir evaluation technology have been established,which lay a foundation for realization of oil and gas exploration objectives.Logging acquisition and evaluation technology for high temperature,high pressure,ultra-deep and low-porosity sandstone gas reservoirs,and efficient development technology for fractured tight sandstone gas reservoirs have been developed,which provide a technical support for efficient exploration&development and rapid production of the Keshen gas field.

Hydrocarbon migration in fracture-cave systems of carbonate reservoirs under tectonic stresses:A modeling study

The Tahe oilfield,located in the southwest of the Akekule nosing structure,northern Tarim basin,was the most prolific oilfield targeting at the Ordovician carbonate reservoirs in China.The reservoir space was dominant with fracture-cave systems commonly induced by tectonics and karstification.Although hydrocarbon production had proceeded for two decades in the Tahe oilfiled,the control of oil and gas accumulations was still doubtful.In this work,the periodic fluid flow induced by cyclic tectonic stresses was proposed as the mechanism of hydrocarbon migration in the fracture-cave systems of carbonate reservoirs.The fracture networks formed conduits for fluid flow,and the fluid pressure in caves transmitted from stress field provided the driving force.The constitutive equations were established among stresses,fracture densities and flow velocities.Four quasi-3D geological models were constructed to simulate the flow velocities on the Ordovician surface of Akekule nosing structure in the critical tectonic stages.The simulated results supplied indicative information on oil and gas migration and accumulation in the tectonic stages.Combining with the oil and gas charge history,a conceptual model was built to reveal the multi-stage oil and gas charge and accumulation in the Ordovician of Akekule nosing structure.