Quantitative proteomic and lipidomics analyses of high oil content GmDGAT1-2 transgenic soybean illustrate the regulatory mechanism of lipoxygenase and oleosin

KEY MESSAGE

Proteomic and lipidomics analyses of WT and GmDGAT1-2 transgenic soybeans showed that GmDGAT1-2 over-expression induced lipoxygenase down-regulatation and oleoin up-regulatation, which significantly changed the compositions and total fatty acid. The main goal of soybean breeding is to increase the oil content. Diacylglycerol acyltransferase (DGAT) is a key rate-limiting enzyme in fatty acid metabolism and may regulate oil content. Herein, 10 GmDGAT genes were isolated from soybean and transferred into wild-type (WT) Arabidopsis. The total fatty acid was 1.2 times higher in T3 GmDGAT1-2 transgenic Arabidopsis seeds than in WT. Therefore, GmDGAT1-2 was transferred into WT soybean (JACK), and four T3 transgenic soybean lines were obtained. The results of high-performance gas chromatography and Soxhlet extractor showed that, compared with those of JACK, oleic acid (18:1), and total fatty acid levels in transgenic soybean plants were much higher, but linoleic acid (18:2) was lower than WT. Palmitic acid (16:0), stearic acid (18:0), and linolenic acid (18:3) were not significantly different. For mechanistic studies, 436 differentially expressed proteins (DEPs) and 180 differentially expressed metabolites (DEMs) were identified between WT (JACK) and transgenic soybean pods using proteomic and lipidomics analyses. Four lipoxygenase proteins were down-regulated in linoleic acid metabolism while four oleosin proteins were up-regulated in the final oil formation. The results showed an increase in the total fatty acid and 18:1 composition, and a decrease in the 18:2 composition of fatty acid. Our study brings new insights into soybean genetic transformation and the deep study of molecular mechanism that changes the total fatty acid, 18:1, and 18:2 compositions in GmDGAT1-2 transgenic soybean.

Light induces carotenoids accumulation in a heterotrophic docosahexaenoic acid producing microalga, Crypthecodinium sp. SUN

In the present study, the effect of various light conditions on carotenoid accumulation in a novel heterotrophic microalga, Crypthecodinium sp. SUN was investigated. The results showed that C. sp. SUN mainly produced γ-carotene and β-carotene. The total carotenoid content could reach to 12.8 mg g^-1 dry weight under high light intensity (100 μmol m^-2 s^-1), which was >100-fold higher than that under dark condition. Besides, along with the light intensity increased, the ROS level in vivo was decreased at 48 h and 72 h. Further study showed that, light could efficiently promote the gene expression of PSY and LCYb, which explain the molecular mechanisms of carotenoids accumulation under light conditions. Meanwhile, slightly inhibited fatty acids accumulation could promote the carotenoids yield. The present work proposed that C. sp. SUN could be a potential carotenoid producer, and provided valuable insight for carotenoids biosynthesis.

Boosting fatty acid synthesis in Rhodococcus opacus PD630 by overexpression of autologous thioesterases

OBJECTIVES

To explore the role of thioesterases in Rhodococcus opacus PD630 by endogenously overexpression in this bacteria for increased lipid production.

RESULTS

Overexpression of four thioesterases from R. opacus PD630 in E. coli led to a 2- to 8-fold increase in C16:1 and C18:1 fatty acids while, when overexpressed in R. opacus PD630, only two recombinants had significant effect on the quantities and compositions of total fatty acid. The contents of total fatty acids (FAs) in two recombinants, pJTE2 (OPAG_00508 thioesterase) and pJTE4 (WP_012687673.1 thioesterase), were 400-460 mg/g (CDW) which is 1.5 times of wild-type strain PD630 (300-350 mg/g CDW), and 20-30 % (w/w) more than that of the control strain PDpJAM2 (330-370 mg/g CDW). The contents of 17:1 and 18:1 fatty acids increased by about 27 and 35 %, respectively, in pJTE2 and by 35 and 20 %, respectively, in pJTE4 compared with the control strain.

CONCLUSIONS

The engineered strains showed improved production of lipid (as total fatty acids), and could also tailor the composition of the fatty acid profile when cultured in mineral salts medium using glucose as sole carbon source.