Mannans and endo-β-mannanases (MAN) in Brachypodium distachyon: Expression profiling and possible role of the BdMAN genes during coleorhiza-limited seed germination

Virginia González-Calle, Cristina Barrero-Sicilia, Pilar Carbonero, Raquel Iglesias-Fernández

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Abstract

Immunolocalization of mannans in the seeds of Brachypodium distachyon reveals the presence of these polysaccharides in the root embryo and in the coleorhiza in the early stages of germination (12h), decreasing thereafter to the point of being hardly detected at 27h. Concurrently, the activity of endo-β-mannanases (MANs; EC 3.2.1.78) that catalyse the hydrolysis of β-1,4 bonds in mannan polymers, increases as germination progresses. The MAN gene family is represented by six members in the Brachypodium genome, and their expression has been explored in different organs and especially in germinating seeds. Transcripts of BdMAN2, BdMAN4 and BdMAN6 accumulate in embryos, with a maximum at 24-30h, and are detected in the coleorhiza and in the root by in situ hybridization analyses, before root protrusion (germination sensu stricto). BdMAN4 is not only present in the embryo root and coleorhiza, but is abundant in the de-embryonated (endosperm) imbibed seeds, while BdMAN2 and BdMAN6 are faintly expressed in endosperm during post-germination (36-42h). BdMAN4 and BdMAN6 transcripts are detected in the aleurone layer. These data indicate that BdMAN2, BdMAN4 and BdMAN6 are important for germination sensu stricto and that BdMAN4 and BdMAN6 may also influence reserve mobilization. Whether the coleorhiza in monocots and the micropylar endosperm in eudicots have similar functions, is discussed.

Original languageEnglish
Pages (from-to)3753-3764
Number of pages12
JournalJournal of Experimental Botany
Volume66
Issue number13
Early online date28 Apr 2015
DOIs
Publication statusPublished - 1 Jul 2015

Keywords

  • BdMAN gene family
  • Brachypodium distachyon
  • coleorhiza
  • endo-β-mannanases
  • germination
  • MAN gene expression
  • mannan immunolocalization
  • mRNA in situ hybridization

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