Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2013
Publication Date: 11/19/2013
Publication URL: http://handle.nal.usda.gov/10113/58812
Citation: Morris, C.F., Geng, H., Beecher, B.S., Ma, D. 2013. A review of the occurrence of grain softness protein-1 genes in wheat (Triticum aestivum L.). Plant Molecular Biology. 83:507-521. Interpretive Summary: This paper presents an in-depth and detailed analysis of the evidence regarding the number of Grain Softness Protein-1 genes in wheat and related taxa. This paper represents both a review and a synthesis. The biological role of Gsp-1 is at present uncertain. Although clearly related to the Puroindolines which are known to exert control over kernel texture, and present at the Hardness locus, Gsp-1 apparently plays no particular role in kernel texture variation. Its role in phylogenetic analysis has proven useful as both Gsp-1 and the puroindolines seem to be under an intermediate level of evolution. For now, one homoeologous-gene-per-genome model should be adopted until a revised model is better supported. In this regard, the present review and synthesis provides a number testable hypotheses, which include the level of polymorphism that may represent (and define) different Gsp-1 alleles, the existence of a fourth Gsp-1 gene, and the high level of naturally-occurring or artifactual gene chimeras. In summary, the present data provides for at most, four Gsp-1 genes in wheat.
Technical Abstract: Grain softness protein-1 (Gsp-1) is a small, 495-bp intronless gene found throughout the Triticeae tribe at the distal end of group 5 chromosomes. With the Puroindolines, it constitutes a key component of the Hardness locus. In the polyploid wheats, Triticum aestivum and T. turgidum, the gene is present in a homoeologous series. Since its discovery, there have been conflicting reports and data as to the number of Gsp-1 genes and the level of sequence polymorphism. In the simplest model, a single Gsp-1 gene is present in each wheat and Aegilops tauschii genome. The present review and synthesis critically re-examines the published and some unpublished data (sequence available in the NCBI nucleotide database). A number of testable hypotheses are identified, and include the level of polymorphism that may represent (and define) different Gsp-1 alleles, the existence of a fourth Gsp-1 gene, and the apparent, at times, high level of naturally-occurring or artifactual gene chimeras. In summary, the present data provides for at most, four Gsp-1 genes in wheat.