Abstract
BackgroundThe wheat dwarfing gene increases lodging resistance, the grain number per spike and harvest index. Dwarf Polish wheat (Triticum polonicum L., 2n = 4x = 28, AABB, DPW), initially collected from Tulufan, Xinjiang, China, carries a semi-dwarfing gene Rht-dp on chromosome 4BS. However, Rht-dp and its dwarfing mechanism are unknown.ResultsHomologous cloning and mapping revealed that Rht-dp is the ‘Green Revolution’ gene Rht-B1b. A haplotype analysis in 59 tetraploid wheat accessions showed that Rht-B1b was only present in T. polonicum. Transcriptomic analysis of two pairs of near-isogenic lines (NILs) of DPW × Tall Polish wheat (Triticum polonicum L., 2n = 4x = 28, AABB, TPW) revealed 41 differentially expressed genes (DEGs) as potential dwarfism-related genes. Among them, 28 functionally annotated DEGs were classed into five sub-groups: hormone-related signalling transduction genes, transcription factor genes, cell wall structure-related genes, reactive oxygen-related genes, and nitrogen regulation-related genes.ConclusionsThese results indicated that Rht-dp is Rht-B1b, which regulates pathways related to hormones, reactive oxygen species, and nitrogen assimilation to modify the cell wall structure, and then limits cell wall loosening and inhibits cell elongation, thereby causing dwarfism in DPW.
Highlights
The wheat dwarfing gene increases lodging resistance, the grain number per spike and harvest index
The separated threshold of plant height with 110 cm was significantly larger than the plant height of Dwarf polish wheat (DPW) with 91.52 ± 2.97 cm, which implied that the effect of Rht-dp on reducing plant height might be partially covered by one or more non-allelic loci
For nitrogen assimilation-related genes, two phosphoenolpyruvate carboxylase kinase 2 (PPCK2) genes and early nodulin (ENOD) were down-regulated; and asparagine synthetase (APS) was up-regulated in the Discussion The GA-insensitive dwarfing gene Rht-B1b is the predominant source of the semi-dwarf growth habit of wheat plants grown in parts of Northern Europe [36], the Mid and Lower Yangtze Valley Autumn-sown Spring Wheat Region in China [37], and the Great Plains Hard Winter Wheat Region in the USA [38]
Summary
The wheat dwarfing gene increases lodging resistance, the grain number per spike and harvest index. The discovery and utilization of semi-dwarfing genes in rice (Oryza sativa) and wheat (Triticum aestivum) triggered the “Green Revolution”, as dwarfism improves lodging resistance [1], and increases the grain number per spike and harvest index [2, 3]. Twenty-two of those genes were discovered from hexaploid wheat, including Rht (Rht-B1b), Rht (Rht-D1b), Rht, and Rht. Twenty-two of those genes were discovered from hexaploid wheat, including Rht (Rht-B1b), Rht (Rht-D1b), Rht, and Rht12 Those genes are widely utilized to breed new cultivars while only Rht and Rht have been cloned [6, 17, 18]. As the parent of hexaploid wheat, tetraploid wheat owns many dwarfing genes, for example, Rht, Rht, Rht, Rht, Rht, and Rht-R107 in Triticum durum [19, 20], Rht in T. turgidum [21], contains Rht-B1f in T. aethiopicum
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