Gene Expression in Plant Lipid Metabolism in Arabidopsis Seedlings

Abstract

Events in plant lipid metabolism are important during seedling establishment. As it has not been experimentally verified whether lipid metabolism in 2- and 5-day-old Arabidopsis thaliana seedlings is diurnally-controlled, quantitative real-time PCR analysis was used to investigate the expression of target genes in acyl-lipid transfer, β-oxidation and triacylglycerol (TAG) synthesis and hydrolysis in wild-type Arabidopsis WS and Col-0. In both WS and Col-0, ACYL-COA-BINDING PROTEIN3 (ACBP3), DIACYLGLYCEROL ACYLTRANSFERASE1 (DGAT1) and DGAT3 showed diurnal control in 2- and 5-day-old seedlings. Also, COMATOSE (CTS) was diurnally regulated in 2-day-old seedlings and LONG-CHAIN ACYL-COA SYNTHETASE6 (LACS6) in 5-day-old seedlings in both WS and Col-0. Subsequently, the effect of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) from the core clock system was examined using the cca1lhy mutant and CCA1-overexpressing (CCA1-OX) lines versus wild-type WS and Col-0, respectively. Results revealed differential gene expression in lipid metabolism between 2- and 5-day-old mutant and wild-type WS seedlings, as well as between CCA1-OX and wild-type Col-0. Of the ACBPs, ACBP3 displayed the most significant changes between cca1lhy and WS and between CCA1-OX and Col-0, consistent with previous reports that ACBP3 is greatly affected by light/dark cycling. Evidence of oil body retention in 4- and 5-day-old seedlings of the cca1lhy mutant in comparison to WS indicated the effect of cca1lhy on storage lipid reserve mobilization. Lipid profiling revealed differences in primary lipid metabolism, namely in TAG, fatty acid methyl ester and acyl-CoA contents amongst cca1lhy, CCA1-OX, and wild-type seedlings. Taken together, this study demonstrates that lipid metabolism is subject to diurnal regulation in the early stages of seedling development in Arabidopsis.

Plant acyl-CoA-binding proteins: An emerging family involved in plant development and stress responses

“…AtACBP3 were regulated by light-dark cycling in Northern-blot analysis and quantitative RT-PCR [28,43,112], and AtACBP4 and AtACBP5 were also shown to be light-dark regulated by Western-blot analysis [156]. AtACBP4 and AtACBP5 were light inducible corresponding well with their proposed role in the protection and transport of plastid-synthesized acyl-CoAs to the ER for extraplastidial lipid biosynthesis [28].…”

Interaction and Regulation Between Lipid Mediator Phosphatidic Acid and Circadian Clock Regulators

“…The rationale was that PA is a central intermediate for the biosynthesis of glycerolipids, including TAG, and that the misregulation of PA due to the defect of the circadian clock might affect the production of TAG, the desired product of many oilseed crops. Also, a previous report indicated that overexpression of CCA1 increases TAG accumulation in Arabidopsis seeds (Hsiao et al, 2014). Compared with seeds of wild-type plants that were grown sideby-side with mutant plants, the content of major seed oil TAG was Figure 10.…”

“…The interconnection between the circadian clock and metabolism is thought to strengthen the function of both processes and enables an organism to adapt efficiently to changes in the environment. Recently, it was reported that some lipid metabolic genes were under circadian control in Arabidopsis and differentially expressed in CCA1/LHY double mutants and CCA1-overexpressing lines (Hsiao et al, 2014;Nakamura et al, 2014). Differences were observed in the levels of triacylglycerols (TAGs) and acyl-CoA between wild-type and the clock gene-altered plants (Hsiao et al, 2014).…”

“…Recently, it was reported that some lipid metabolic genes were under circadian control in Arabidopsis and differentially expressed in CCA1/LHY double mutants and CCA1-overexpressing lines (Hsiao et al, 2014;Nakamura et al, 2014). Differences were observed in the levels of triacylglycerols (TAGs) and acyl-CoA between wild-type and the clock gene-altered plants (Hsiao et al, 2014). However, the interconnection between lipid metabolism and the circadian clock is not fully understood, and the cellular mediators that act as conduits to integrate the circadian clock with metabolism remain unknown in plants.…”

The overexpression of rice ACYL‐CoA‐BINDING PROTEIN2 increases grain size and bran oil content in transgenic rice

“…Confocal microscopy on rice aleurone cells was carried out as previously described (Hsiao et al ., 2014b) with modifications. Next 1‐day‐old imbibed rice seeds were infiltrated with an aqueous solution of Nile red (Sigma) to visualize lipid bodies in the rice aleurone.…”