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Title: Physical Mapping and a new puroindoline b-2 gene in wheat

item Morris, Craig

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2009
Publication Date: 2/1/2010
Citation: Chen, F., Beecher, B.S., Morris, C.F. 2010. Physical Mapping and a new puroindoline b-2 gene in wheat. Theor. Appl. Genet. 120:745-751.

Interpretive Summary: Puroindoline proteins are present throughout the Triticeae tribe of the Poaceae (Gramineae), including wheat, rye, barley, and the wild relatives of wheat. In wheat, puroindolines exist as two expressed genes, Puroindoine a and Puroindoline b, on the end of the short arm of chromosome 5 (5DS). An exception to this situation lies with the tetraploid (AABB) wheats (T. turgidum), which includes cultivated durum. The presence of Puroindoine a D1a (Pina D1a) and Puroindoline b D1a (Pinb D1a) are associated with soft kernel texture in soft wheat varieties. Recently Wilkinson et al. (2008) reported three new puroindoline gene-like sequences in hexaploid wheat. The genes shared close homology with Pinb and hence were designated Pinb 'variants.' This publication provides evidence to show that the three variants reported by Wilkinson et al. (2008) exist as a homoeologous series, wherein variant 1 (Pinb 2v1) resides on the short arm of chromosome 7D (7DS), variant 2 (Pinb 2v2) resides on 7BL, and variant 3 resides on 7B; variant 3 may not be allelic to variant 2. Lastly, this publication reports the discovery of a fourth variant (Pinb 2v4) which resides on 7AL.

Technical Abstract: Puroindoline a and b proteins soften the endosperm of wheat kernels. When the underlying puroindoline genes are altered by mutation or are deleted, kernels become harder. Thus puroindoline a and b (Pina and Pinb) play an important role in wheat quality and utilization. Recently, additional Pinb genes have been reported. In the present report, we provide corroborating coding and additional 5' and 3' flanking sequence for three Pinb variants: Pinb 2v1, Pinb 2v2, and Pinb 2v3. Additionally, a new Pinb variant, Pinb 2v4, is reported. All four variants were physically mapped using Chinese Spring (CS) diteolosomics, nullisomic-tetrasomics, and CS-Cheyenne disomic substitution lines. Results place Pinb 2v1 on 7DS, Pinb 2v2 on 7BL, Pinb 2v3 on 7B, and Pinb 2v4 on 7AL. Pinb 2v1 and Pinb 2v4 were present in all cvs. examined: CS, Cheyenne, Recital, Wichita and Winsome. Pinb 2v2 was present in CS, Recital and Winsome; Pinb 2v3 was present in Cheyenne and Wichita. These results are not wholly consistent with prior research and additional studies will be required to reconcile discrepancies. The discovery of Pinb 2v4 and the mapping of all four variants will contribute to a better understanding of gene duplication events in wheat and their bearing on wheat kernel texture and grain utilization.