title: The deposition and characterization of starch in Brachypodium distachyon.
abstract: Brachypodium distachyon is a non-domesticated cereal. Nonetheless, Brachypodium was recently introduced as a model plant for temperate cereals. This study compares grain starch metabolism in Brachypodium and barley (Hordeum vulgare). In Brachypodium, we identified and annotated 28 genes involved in starch metabolism and identified important motifs including transit peptides and putative carbohydrate-binding modules (CBMs) of the families CBM20, CBM45, CBM48, and CBM53. Starch content was markedly lower in Brachypodium grains (12%) compared to barley grains (47%). Brachypodium starch granules were doughnut shaped and bimodally distributed into distinct small B-type (2.5-10 µm) and very small C-type (0.5-2.5 µm) granules. Large A-type granules, typical of cereals, were absent. Starch-bound phosphate, important for starch degradation, was 2-fold lower in Brachypodium compared with barley indicating different requirements for starch mobilization. The amylopectin branch profiles were similar and the amylose content was only slightly higher compared with barley cv. Golden Promise. The crystallinity of Brachypodium starch granules was low (10%) compared to barley (20%) as determined by wide-angle X-ray scattering (WAXS) and molecular disorder was confirmed by differential scanning calorimetry (DSC). The expression profiles in grain for most genes were distinctly different for Brachypodium compared to barley, typically showing earlier decline during the course of development, which can explain the low starch content and differences in starch molecular structure and granule characteristics. High transitory starch levels were observed in leaves of Brachypodium (2.8% after 14h of light) compared to barley (1.9% after 14h of light). The data suggest important pre-domesticated features of cereals.
authors: Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, DK-1871, Denmark.
authors: Vanja
authors: V
authors: Tanackovic
authors: Nordic Genetic Resource Centre, P.O. Box 41, SE-230 53 Alnarp, Sweden.
authors: Jan T
authors: JT
authors: Svensson
authors: Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, DK-1871, Denmark.
authors: Susanne L
authors: SL
authors: Jensen
authors: UR1268 Biopolymeres Interactions Assemblages, INRA, F-44300 Nantes, France.
authors: Alain
authors: A
authors: Buléon
authors: Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, DK-1871, Denmark abl@plen.ku.dk.
authors: Andreas
authors: A
authors: Blennow
mesh_terms: D058431:Brachypodium / Q000378:metabolism*; D002152:Calorimetry, Differential Scanning; D001467:Hordeum / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D013213:Starch / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D013213:Starch
keywords: Barley; Brachypodium distachyon; endosperm; grass domestication; starch biosynthesis; starch granule.