Hormone-mediated growth dynamics of the barley pericarp as revealed by magnetic resonance imaging and transcript profiling.
The shape of the maternal pericarp affects cereal grain mass and yield. Pericarp growth was analysed by magnetic resonance imaging (MRI), revealing topological maps of mobile water in developing pericarp of barley (Hordeum vulgare) and displaying tissue regions actively elongating in specific temporal-spatial patterns. Correlation analysis of MRI signals and growth rates reveals that growth in length is mediated by dorsal and also lateral rather than ventral regions. Growth in thickness is related to ventral regions. Switching from dorsal to ventral growth is associated with differential expression of axial regulators of the HD-ZipIII and Kanadi/Ettin types, and NPH3 photoreceptors, suggesting light-mediated auxin re-distribution. Auxin increases with the highest levels in the basal pericarp at 6 days after fertilization (DAF), together with transcriptionally up-regulated auxin transport and signalling. Gibberellin biosynthesis is transcriptionally up-regulated only later, and levels of bioactive gibberellins increase from 7 to 13 DAF, with higher levels in ventral than dorsal regions. Differential gene expression related to cell expansion indicates genes related to apoplast acidification, wall relaxation, sugar cleavage, water transport, and cell wall biosynthesis. Candidate genes potentially involved in pericarp extension are distinguished by their temporal expression, representing potential isoforms responsible for dorsal-mediated early growth in length or ventral-mediated late growth in thickness.
Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
Rainer
R
Pielot
Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
Stefan
S
Kohl
Fraunhofer Institut für Biomedizinische Technik (IBMT) Simulation, Visualization & Magnetic Resonance, Ensheimer Str. 48, D-66386 St. Ingbert, Germany.
Bertram
B
Manz
Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
Twan
T
Rutten
Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
Diana
D
Weier
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany ASCR and Palacký University, Šlechtitelů 11, CZ-78371, Olomouc, Czech Republic.
Danuše
D
Tarkowská
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany ASCR and Palacký University, Šlechtitelů 11, CZ-78371, Olomouc, Czech Republic.
Jakub
J
Rolčík
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany ASCR and Palacký University, Šlechtitelů 11, CZ-78371, Olomouc, Czech Republic.
Miroslav
M
Strnad
Fraunhofer Institut für Biomedizinische Technik (IBMT) Simulation, Visualization & Magnetic Resonance, Ensheimer Str. 48, D-66386 St. Ingbert, Germany.
Frank
F
Volke
Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany weber@ipk-gatersleben.de.
Hans
H
Weber
Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany weber@ipk-gatersleben.de.
Winfriede
W
Weschke
D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism; D001467:Hordeum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
D005875:Gibberellins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins
Auxin; barley pericarp; cell expansion; directed growth; gibberellic acid; grain length; growth dynamics; magnetic resonance imaging; transcript profiling.