Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 117, Issue 46, Pages 28708-28718Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2009418117
Keywords
solid stem; wheat; copy number variation (CNV); Dof transcription factor; programmed cell death (PCD)
Categories
Funding
- Genome Canada
- Western Grain Research Foundation
- Government of Saskatchewan
- Saskatchewan Wheat Development Commission
- Alberta Wheat Commission
- Manitoba Agriculture
- Viterra
- Manitoba Wheat and Barley Growers Association
- Secan
- National Research Council Wheat Flagship Program
- Global Institute for Food Security
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Stem solidness is an important agronomic trait of durum (Triticum turgidum L. var. durum) and bread (Triticum aestivum L.) wheat that provides resistance to the wheat stem sawfly. This dominant trait is conferred by the SSt7 locus on chromosome 3B. However, the molecular identity and mechanisms underpinning stem solid-ness have not been identified. Here, we demonstrate that copy number variation of TdDof, a gene encoding a putative DNA binding with one finger protein, controls the stem solidness trait in wheat. Using map-based cloning, we localized TdDof to within a physical interval of 2.1 Mb inside the SSt7 locus. Molecular analysis revealed that hollow-stemmed wheat cultivars such as Kronos carry a single copy of TdDof, whereas solid-stemmed cultivars such as CDC Fortitude carry multiple identical copies of the gene. Deletion of all TdDof copies from CDC Fortitude resulted in the loss of stem solidness, whereas the transgenic overexpression of TdDof restored stem solidness in the TdDof deletion mutant pithless7 and conferred stem solidness in Kronos. In solid stemmed cultivars, increased TdDof expression was correlated with the down-regulation of genes whose orthologs have been implicated in programmed cell death (PCD) in other species. Anatomical and histochemical analyses revealed that hollow-stemmed lines had stronger PCD-associated signals in the pith cells compared to solid-stemmed lines, which suggests copy number dependent expression of TdDof could be directly or indirectly involved in the negative regulation of PCD. These findings provide opportunities to manipulate stem development in wheat and other monocots for agricultural or industrial purposes.
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