Rising CO 2 concentration altered wheat grain proteome and flour rheological characteristics Nimesha Fernando a , Joe Panozzo b , Michael Tausz c , Robert Norton d , Glenn Fitzgerald b , Alamgir Khan e , Saman Seneweera a,f,⇑ a Department of Agriculture and Food Systems, Melbourne School of Land and Environment, The University of Melbourne, Water Street, Creswick, Victoria 3363, Australia b Department of Primary Industries, Natimuk Road, Private Box 260, Horsham, Victoria 3401, Australia c Department of Forest and Ecosystem Science, Melbourne School of Land and Environment, The University of Melbourne, Water Street, Creswick, Victoria 3363, Australia d International Plant Nutrition Institute, 54 Florence St, Horsham, Victoria 3400, Australia e Australian Proteome Analysis Facility (APAF), Level 4, Building F7B, Research Park Drive, Macquarie University, Sydney, NSW 2109, Australia f Centre for Systems Biology, University of Southern Queensland, Toowoomba, QLD 4350, Australia article info Article history: Received 10 February 2014 Received in revised form 14 June 2014 Accepted 7 July 2014 Available online 14 July 2014 Keywords: Free-Air Carbon Dioxide Enrichment (FACE) Grain proteome High molecular weight glutenin sub units Grain protein Bread volume abstract Wheat cv. H45 was grown under ambient CO 2 concentration and Free Air CO 2 Enrichment (FACE; e[CO 2 ], 550 lmol CO 2 mol 1 ). The effect of FACE on wheat grain proteome and associated changes in the flour rheological properties was investigated. A comparative proteomic analysis was performed using 2-D-DIGE followed by MALDI/TOF-MS. Total grain protein concentration was decreased by 9% at e[CO 2 ]. Relative abundance of three high molecular weight glutenin sub units (HMW-GS) were decreased at e[CO 2 ]. In contrast, relative abundance of serpins Z1C and 1-Cys peroxiredoxin was increased at e[CO 2 ]. Elevated [CO 2 ] also decreased the bread volume (by 11%) and dough strength (by 7%) while increased mixing time. However, dough extensibility and dough stability were unchanged at elevated [CO 2 ]. These findings suggest that e[CO 2 ] has a major impact on gluten protein concentration which is associated lower bread quality at e[CO 2 ]. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The current atmospheric carbon dioxide concentration ([CO 2 ]) has reached the level of 400 lmol CO 2 mol 1 and is predicted to be ±550 lmol CO 2 mol 1 by the middle of the 21st century accord- ing to the Intergovernmental Panel on Climate Change (IPCC) under ‘‘mid-range’’ emission scenario A1B (Carter, Jones, & Lu, 2007). This will have a direct impact on the growth and develop- ment and yield formation of crops, particularly for C 3 plants includ- ing wheat and rice. It is predicted that grain yield will increase by 15–17% under an atmospheric CO 2 concentration (a[CO 2 ]) of about 550 lmol CO 2 mol 1 (Leakey et al., 2009). However, the positive influence of [CO 2 ] on plant growth and grain yield is counteracted by inferior grain quality (Fernando, Panozzo, Tausz, Norton, Fitzgerald, Myers, et al., 2012; Fernando, Panozzo, Tausz, Norton, Fitzgerald, & Seneweera, 2012; Högy, Wieser, et al., 2009). Mostly, wheat is consumed after processing, therefore, end product quality is important (Shewry, 2009). Wheat end product quality is dependent on the functional properties of flour, which is mainly determined by grain protein concentration and composi- tion (Shewry, 2009). Protein concentration in wheat grains varies from 8% to 20% and the major protein fractions can be classified into three main groups, namely structural, metabolic and storage proteins based on their functional characteristics (Shewry, Tatham, Forde, Kreis, & Miflin, 1986). Storage proteins are consid- ered as gluten proteins, which form viscoelastic networks during dough mixing and are highly correlated with the rheological prop- erties of wheat flour (Shewry, 2009). According to the primary structure, gluten protein can be classified into three main groups, each group consisting of two or three protein types: high molecular weight (HMW) prolamins (consisting of x- and y- type HMW glutenin subunits), S-poor prolamins (comprises x-gliadins) and S-rich prolamins (includes a-, b-, and c- type gliadins and low molecular weight (LMW) glu- tenin subunits) (Shewry et al., 1986). Gliadins are mainly mono- meric proteins that make up 35–45% of the total wheat protein (molecular weight range from 28 to 55 kD) and are soluble in aque- ous alcohol. Glutenins are insoluble and are larger polymeric, http://dx.doi.org/10.1016/j.foodchem.2014.07.044 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Centre for Systems Biology, University of Southern Queensland, Toowoomba, QLD 4350, Australia. Tel.: +61 746315525, mobile: +61 401879853. E-mail address: saman.seneweera@usq.edu.au (S. Seneweera). Food Chemistry 170 (2015) 448–454 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem