Proteomic analysis of metabolic mechanisms associated with fatty acid biosynthesis during Styrax tonkinensis kernel development

Proteome Landscape during Ripening of Solid Endosperm from Two Different Coconut Cultivars Reveals Contrasting Carbohydrate and Fatty Acid Metabolic Pathway Modulation

Cocos nucifera L. is a crop grown in the humid tropics. It is grouped into two classes of varieties: dwarf and tall; regardless of the variety, the endosperm of the coconut accumulates carbohydrates in the early stages of maturation and fatty acids in the later stages, although the biochemical factors that determine such behavior remain unknown. We used tandem mass tagging with synchronous precursor selection (TMT-SPS-MS3) to analyze the proteomes of solid endosperms from Yucatan green dwarf (YGD) and Mexican pacific tall (MPT) coconut cultivars. The analysis was conducted at immature, intermediate, and mature development stages to better understand the regulation of carbohydrate and lipid metabolisms. Proteomic analyses showed 244 proteins in YGD and 347 in MPT; from these, 155 proteins were shared between both cultivars. Furthermore, the proteomes related to glycolysis, photosynthesis, and gluconeogenesis, and those associated with the biosynthesis and elongation of fatty acids, were up-accumulated in the solid endosperm of MPT, while in YGD, they were down-accumulated. These results support that carbohydrate and fatty acid metabolisms differ among the developmental stages of the solid endosperm and between the dwarf and tall cultivars. This is the first proteomics study comparing different stages of maturity in two contrasting coconut cultivars and may help in understanding the maturity process in other palms.

The Combined Analysis of Transcriptome and Antioxidant Enzymes Revealed the Mechanism of EBL and ZnO NPs Enhancing Styrax tonkinensis Seed Abiotic Stress Resistance

As global climate change worsens, trees will have difficulties adapting to abiotic pressures, particularly in the field, where environmental characteristics are difficult to control. A prospective commercial and ornamental tree species, Styrax tonkinensis, has its seed oil output and quality reduced as a result, which lowers the economic benefits. This necessitates growers to implement efficient strategies to increase the seeds of woody biofuel species' tolerance to abiotic stress. Numerous studies have shown that ZnO nanoparticles (NPs), a new material, and BRs assist plants to increase their resilience to abiotic stress and subsequently adapt to it. However, there have not been many investigations into S. tonkinensis seed resistance. In this study, we examined the changes in antioxidant enzyme activities and transcriptomic results of S. tonkinensis seeds throughout the seed development period to investigate the effects of 24-epibrassinolide (EBL), one of the BRs, and ZnO NPs treatments alone or together on the stress resistance of S. tonkinensis seeds. On 70, 100, and 130 days after flowering (DAF), spraying EBL or ZnO NPs increased the activity of antioxidant enzymes (POD, SOD, and CAT) in S. tonkinensis seeds. Moreover, when the EBL and ZnO NPs were sprayed together, the activities of antioxidant enzymes were the strongest, which suggests that the positive effects of the two can be superimposed. On 70 and 100 DAF, the EBL and ZnO NPs treatments improved seed stress resistance, mostly through complex plant hormone crosstalk signaling, which includes IAA, JA, BR, and ABA signaling. Additionally, ABA played an essential role in hormone crosstalk, while, on 130 DAF, due to the physiological characteristics of seeds themselves in the late stage of maturity, the improvement in seed stress resistance by EBL and ZnO NPs was related to protein synthesis, especially late embryogenesis-abundant protein (LEA), and other nutrient storage in seeds. Spraying EBL and ZnO NPs during the seed growth of S. tonkinensis could significantly increase seed stress resistance. Our findings provide fresh perspectives on how cultural practices can increase abiotic stress tolerance in woody seedlings.

Effects of Fruit Shading on Gene and Protein Expression During Starch and Oil Accumulation in Developing Styrax tonkinensis Kernels

Styrax tonkinensis has great potential as a biofuel feedstock source having industrial oilseeds with excellent fatty acids (FAs) composition and good fuel properties. Photosynthesis in the developing pericarp could affect the carbon distribution in kernel. During kernel development, more carbon sources are allocated to starch rather than lipid, when the pericarp photosynthesis is reduced by fruit shading treatment. After shading the fruits at 50 days after flowering (DAF), samples of shaded fruit (FSK) and controls (CK) were collected at 80 DAF and analyzed using the proteomic method. We identified 3,181 proteins, of which 277 were differentially expressed proteins, all downregulated in the FSK group. There were 56 proteins found involved in carbohydrate metabolism and lipid biosynthesis leading to oil accumulation with their iTRAQ ratios of FSK/CK ranging from 0.7123 to 1.1075. According to the qRT-PCR analyses, the key genes related to FA and triacylglycerol (TAG) biosynthesis were significantly downregulated between 60 and 90 DAF especially at 80 DAF, while the key genes involved in starch biosynthesis and FA desaturase had no significant difference between the two groups at 80 DAF. Fruit shading is a negative treatment for lipid accumulation but not starch accumulation by restraining enzymic protein expression involved in FA and TAG biosynthesis during S. tonkinensis kernel development.