A carbohydrate-binding protein, B-GRANULE CONTENT 1, influences starch granule size distribution in a dose-dependent manner in polyploid wheat

Tansy Chia, Marcella Chirico, Rob King, Ricardo Ramirez Gonzalez, Benedetta Saccomanno, James Simmonds, Martin Trick, Cristobal Uauy, Tamara Verhoeven, Kay Trafford

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In Triticeae endosperm (e.g. wheat and barley), starch granules have a bimodal size distribution (with A- and B-type granules) whereas in other grasses the endosperm contains starch granules with a unimodal size distribution. Here, we identify the gene, BGC1 (B-GRANULE CONTENT 1), responsible for B-type starch granule content in Aegilops and wheat. Orthologues of this gene are known to influence starch synthesis in diploids such as rice, Arabidopsis, and barley. However, using polyploid Triticeae species, we uncovered a more complex biological role for BGC1 in starch granule initiation: BGC1 represses the initiation of A-granules in early grain development but promotes the initiation of B-granules in mid grain development. We provide evidence that the influence of BGC1 on starch synthesis is dose dependent and show that three very different starch phenotypes are conditioned by the gene dose of BGC1 in polyploid wheat: normal bimodal starch granule morphology; A-granules with few or no B-granules; or polymorphous starch with few normal A- or B-granules. We conclude from this work that BGC1 participates in controlling B-type starch granule initiation in Triticeae endosperm and that its precise effect on granule size and number varies with gene dose and stage of development.
Original languageEnglish
Pages (from-to)105-115
Number of pages11
JournalJournal of Experimental Botany
Issue number1
Early online date21 Oct 2019
Publication statusPublished - Jan 2020


  • Aegilops
  • B-type starch granule content
  • TILLING mutant
  • Triticeae
  • crop breeding
  • granule size distribution
  • polymorphous starch
  • starch granule initiation
  • wheat grain

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