title: Analysis of the Rice ADP-Glucose Transporter (OsBT1) Indicates the Presence of Regulatory Processes in the Amyloplast Stroma That Control ADP-Glucose Flux into Starch.
abstract: Previous studies showed that efforts to further elevate starch synthesis in rice (Oryza sativa) seeds overproducing ADP-glucose (ADPglc) were prevented by processes downstream of ADPglc synthesis. Here, we identified the major ADPglc transporter by studying the shrunken3 locus of the EM1093 rice line, which harbors a mutation in the BRITTLE1 (BT1) adenylate transporter (OsBt1) gene. Despite containing elevated ADPglc levels (approximately 10-fold) compared with the wild-type, EM1093 grains are small and shriveled due to the reduction in the amounts and size of starch granules. Increases in ADPglc levels in EM1093 were due to their poor uptake of ADP-[(14)C]glc by amyloplasts. To assess the potential role of BT1 as a rate-determining step in starch biosynthesis, the maize ZmBt1 gene was overexpressed in the wild-type and the GlgC (CS8) transgenic line expressing a bacterial glgC-TM gene. ADPglc transport assays indicated that transgenic lines expressing ZmBT1 alone or combined with GlgC exhibited higher rates of transport (approximately 2-fold), with the GlgC (CS8) and GlgC/ZmBT1 (CS8/AT5) lines showing elevated ADPglc levels in amyloplasts. These increases, however, did not lead to further enhancement in seed weights even when these plant lines were grown under elevated CO2. Overall, our results indicate that rice lines with enhanced ADPglc synthesis and import into amyloplasts reveal additional barriers within the stroma that restrict maximum carbon flow into starch.
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Bilal
authors.identifier: http://orcid.org/0000-0003-4610-0317
authors.initials: B
authors.lastname: Cakir
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Shota
authors.initials: S
authors.lastname: Shiraishi
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Aytug
authors.identifier: http://orcid.org/0000-0002-4666-5679
authors.initials: A
authors.lastname: Tuncel
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsusaka
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Ryosuke
authors.identifier: http://orcid.org/0000-0003-1439-412X
authors.initials: R
authors.lastname: Satoh
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Salvinder
authors.initials: S
authors.lastname: Singh
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Naoko
authors.identifier: http://orcid.org/0000-0002-6792-2232
authors.initials: N
authors.lastname: Crofts
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Yuko
authors.initials: Y
authors.lastname: Hosaka
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Naoko
authors.identifier: http://orcid.org/0000-0002-6792-2232
authors.initials: N
authors.lastname: Fujita
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.).
authors.forename: Seon-Kap
authors.identifier: http://orcid.org/0000-0001-9552-5341
authors.initials: SK
authors.lastname: Hwang
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.) okita@wsu.edu hikaru.satoh.682@m.kyushu-u.ac.jp.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Satoh
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (B.C., A.T., S.-K.H., T.W.O.);Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan (S.Sh., H.M., R.S., H.S.);Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-785013, Assam, India (S.Si.); andDepartment of Biological Production, Akita Prefectural University, Akita City, Akita 010-01195, Japan (N.C., Y.H., N.F.) okita@wsu.edu hikaru.satoh.682@m.kyushu-u.ac.jp.
authors.forename: Thomas W
authors.identifier: http://orcid.org/0000-0002-2246-0599
authors.initials: TW
authors.lastname: Okita
mesh_terms: D000245:Adenosine Diphosphate Glucose / Q000378:metabolism*; D017343:Genes, Plant; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D018087:Plastids / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D013213:Starch / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology / Q000235:genetics
chemical_list: D051246:Glucose Transport Proteins, Facilitative; D010940:Plant Proteins; D011994:Recombinant Proteins; D000245:Adenosine Diphosphate Glucose; D013213:Starch