Callose Synthase GSL7 Is Necessary for Normal Phloem Transport and Inflorescence Growth in Arabidopsis

One isoform of callose synthase, Glucan Synthase-Like7 (GSL7), is tightly coexpressed with two isoforms of sucrose synthase (SUS5 and SUS6) known to be confined to phloem sieve elements in Arabidopsis (Arabidopsis thaliana). Investigation of the phenotype of gsl7 mutants of Arabidopsis revealed that...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 2011-01, Vol.155 (1), p.328-341
Main Authors: Barratt, D.H. Paul, Kölling, Katharina, Graf, Alexander, Pike, Marilyn, Calder, Grant, Findlay, Kim, Zeeman, Samuel C., Smith, Alison M.
Format: Article
Language:English
Subjects:
Arabidopsis - enzymology
Arabidopsis - genetics
Arabidopsis - growth & development
Arabidopsis - ultrastructure
Arabidopsis Proteins - genetics
Arabidopsis Proteins - metabolism
BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES
Biological and medical sciences
Biological Transport - drug effects
Carbohydrate Metabolism - drug effects
Carbon Isotopes
Flowering
Fundamental and applied biological sciences. Psychology
Gene Expression Regulation, Plant - drug effects
Genes, Plant - genetics
Glucans - metabolism
Glucosyltransferases - genetics
Glucosyltransferases - metabolism
Inflorescence - anatomy & histology
Inflorescence - genetics
Inflorescence - growth & development
Inflorescence - ultrastructure
Inflorescences
Leaves
Mutation - genetics
Phloem
Phloem - cytology
Phloem - drug effects
Phloem - metabolism
Phloem - ultrastructure
Plant growth
Plant Leaves - drug effects
Plant Leaves - metabolism
Plant physiology and development
Plant roots
Plant Roots - drug effects
Plant Roots - metabolism
Plant Roots - ultrastructure
Plant Stems - anatomy & histology
Plant Stems - drug effects
Plant Stems - metabolism
Plant Stems - ultrastructure
Plants
Sieve elements
Sieve plates
Stems
Sucrose - pharmacology
Transcription, Genetic - drug effects
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Summary:One isoform of callose synthase, Glucan Synthase-Like7 (GSL7), is tightly coexpressed with two isoforms of sucrose synthase (SUS5 and SUS6) known to be confined to phloem sieve elements in Arabidopsis (Arabidopsis thaliana). Investigation of the phenotype of gsl7 mutants of Arabidopsis revealed that the sieve plate pores of stems and roots lack the callose lining seen in wild-type plants. Callose synthesis in other tissues of the plant appears to be unaffected. Although gsl7 plants show only minor phenotypic alterations during vegetative growth, flowering stems are reduced in height and all floral parts are smaller than those of wild-type plants. Several lines of evidence suggest that the reduced growth of the inflorescence is a result of carbohydrate starvation. Levels of sucrose, hexoses, and starch are lower in the terminal bud clusters of gsl7 than in those of wild-type plants. Transcript levels of "starvation" genes expressed in response to low sugars are elevated in the terminal bud clusters of gsl7 plants, at the end of the night, and during an extended night. Pulse-chase experiments with ¹₄CO₂ show that transport of assimilate in the flowering stem is much slower in gsl7 mutants than in wild-type plants. We suggest that the callóse lining of sieve plate pores is essential for normal phloem transport because it confers favorable flow characteristics on the pores.
ISSN:0032-0889
1532-2548
1532-2548
DOI:10.1104/pp.110.166330