title: Plastidic phosphoglucomutase and ADP-glucose pyrophosphorylase mutants impair starch synthesis in rice pollen grains and cause male sterility.
abstract: To elucidate the starch synthesis pathway and the role of this reserve in rice pollen, we characterized mutations in the plastidic phosphoglucomutase, OspPGM, and the plastidic large subunit of ADP-glucose (ADP-Glc) pyrophosphorylase, OsAGPL4 Both genes were up-regulated in maturing pollen, a stage when starch begins to accumulate. Progeny analysis of self-pollinated heterozygous lines carrying the OspPGM mutant alleles, osppgm-1 and osppgm-2, or the OsAGPL4 mutant allele, osagpl4-1, as well as reciprocal crosses between the wild type (WT) and heterozygotes revealed that loss of OspPGM or OsAGPL4 caused male sterility, with the former condition rescued by the introduction of the WT OspPGM gene. While iodine staining and transmission electron microscopy analyses of pollen grains from homozygous osppgm-1 lines produced by anther culture confirmed the starch null phenotype, pollen from homozygous osagpl4 mutant lines, osagpl4-2 and osagpl4-3, generated by the CRISPR/Cas system, accumulated small amounts of starch which were sufficient to produce viable seed. Such osagpl4 mutant pollen, however, was unable to compete against WT pollen successfully, validating the important role of this reserve in fertilization. Our results demonstrate that starch is mainly polymerized from ADP-Glc synthesized from plastidic hexose phosphates in rice pollen and that starch is an essential requirement for successful fertilization in rice.
authors: Graduate School of Biotechnology & Crop Biotech Institute, Kyung Hee University, Yongin 17104, Korea.
authors: Sang-Kyu
authors: SK
authors: Lee
authors: Graduate School of Biotechnology & Crop Biotech Institute, Kyung Hee University, Yongin 17104, Korea.
authors: Joon-Seob
authors: JS
authors: Eom
authors: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors: Seon-Kap
authors: SK
authors: Hwang
authors: Department of Southern Area Crop Science, National Institute of Crop Science, Rural Development Administration, Milyang 50424, Korea.
authors: Dongjin
authors: D
authors: Shin
authors: Graduate School of Biotechnology & Crop Biotech Institute, Kyung Hee University, Yongin 17104, Korea.
authors: Gynheung
authors: G
authors: An
authors: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors: Thomas W
authors: TW
authors: Okita
authors: Graduate School of Biotechnology & Crop Biotech Institute, Kyung Hee University, Yongin 17104, Korea jjeon@khu.ac.kr.
authors: Jong-Seong
authors: JS
authors: Jeon
mesh_terms: D005298:Fertility / Q000502:physiology; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000378:metabolism* / Q000502:physiology; D008853:Microscopy; D009154:Mutation; D012275:Oryza / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D010733:Phosphoglucomutase / Q000378:metabolism* / Q000502:physiology; D011058:Pollen / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013213:Starch / Q000096:biosynthesis*
chemical_list: D013213:Starch; D051599:Glucose-1-Phosphate Adenylyltransferase; D010733:Phosphoglucomutase
keywords: 
  Oryza sativa
  ; ADP-glucose pyrophosphorylase; male sterility; phosphoglucomutase; plastid; pollen; starch.