Barley plants over-expressing the NAC transcription factor gene HvNAC005 show stunting and delay in development combined with early senescence

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  • Michael W Christiansen
  • ,
  • Colette Matthewman
  • ,
  • Dagmara Podzimska-Sroka
  • ,
  • Charlotte O'Shea, Department of Biology, University of Copenhagen, Danmark
  • Søren Lindemose, Department of Biology, University of Copenhagen, Danmark
  • Niels Erik Møllegaard, Department of Cellular and Molecular Medicine, University of Copenhagen, Danmark
  • Inger B Holme
  • Kim Hebelstrup
  • Karen Skriver, Department of Biology, University of Copenhagen, Danmark
  • Per L Gregersen

The plant-specific NAC transcription factors have attracted particular attention because of their involvement in stress responses, senescence, and nutrient remobilization. The HvNAC005 gene of barley encodes a protein belonging to subgroup NAC-a6 of the NAC family. This study shows that HvNAC005 is associated with developmental senescence. It was significantly up-regulated following ABA treatment, supported by ABA-responsive elements in its promoter, but it was not up-regulated during dark-induced senescence. The C-termini of proteins closely related to HvNAC005 showed overall high divergence but also contained conserved short motifs. A serine- and leucine-containing central motif was essential for transcriptional activity of the HvNAC005 C-terminus in yeast. Over-expression of HvNAC005 in barley resulted in a strong phenotype with delayed development combined with precocious senescence. The over-expressing plants showed up-regulation of genes involved with secondary metabolism, hormone metabolism, stress, signalling, development, and transport. Up-regulation of senescence markers and hormone metabolism and signalling genes supports a role of HvNAC005 in the cross field of different hormone and signalling pathways. Binding of HvNAC005 to promoter sequences of putative target genes containing the T[G/A]CGT core motif was shown by direct protein-DNA interactions of HvNAC005 with promoters for two of the up-regulated genes. In conclusion, HvNAC005 was shown to be a strong positive regulator of senescence and so is an obvious target for the fine-tuning of gene expression in future attempts to improve nutrient remobilization related to the senescence process in barley.

TidsskriftJournal of Experimental Botany
Sider (fra-til)5259-5273
Antal sider15
StatusUdgivet - sep. 2016

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