Title Gene expression in plant lipid metabolism in Arabidopsisseedlings

Events in plant lipid metabolism are important during seedling establishment. As it has not been experimentally verified whether lipid metabolism in 2and 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, b-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 2and 5-day-old seedlings. Also, COMATOSE (CTS) was diurnally regulated in 2-day-old seedlings and LONG-CHAIN ACYL-COA SYNTHETASE6 (LACS6) in 5day-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 CCA1overexpressing (CCA1-OX) lines versus wild-type WS and Col-0, respectively. Results revealed differential gene expression in lipid metabolism between 2and 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 Col0, consistent with previous reports that ACBP3 is greatly affected by light/dark cycling. Evidence of oil body retention in 4and 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. Citation: Hsiao A-S, Haslam RP, Michaelson LV, Liao P, Napier JA, et al. (2014) Gene Expression in Plant Lipid Metabolism in Arabidopsis Seedlings. PLoS ONE 9(9): e107372. doi:10.1371/journal.pone. 0107372 Editor: Christopher Beh, Simon Fraser University, Canada Received May 26, 2014; Accepted August 9, 2014; Published September 29, 2014 Copyright: 2014 Hsiao et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by the Wilson and Amelia Wong Endowment Fund and the Hong Kong Research Grants Council (HKU765813M). ASH and PL were supported by a HKU Postgraduate Studentship and a University Postgraduate Fellowship, respectively. Work done by JAN, LVM and RPH investigating the dynamics of seed oil synthesis was funded by an Institute Strategic Program Grant (Designing Seeds) from the BBSRC (United Kingdom). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * Email: mlchye@hkucc.hku. hk