Effect of Multiple Copies of Puroindoline Genes on Grain Softness
2004
End use quality in wheat (Triticum aestivum L.) is primarily determined by grain hardness or texture. The puroindoline genes Pina and Pinb are the main components of the 15-kDa friabilin protein, which is associated with kernel softness. Pina and Pinb are expressed in diploid wheat species but are silent in tetraploid wheat. The active puroindolines in hexaploid, or bread wheat, were derived from Aegilops tauschii Coss., the D genome diploid donor. The focus of this study was to incorporate active puroindoline genes into the A and B genomes of bread wheat and analyze their impact upon grain softness. Functional copies of Pina and Pinb in disomic substitution lines of T. monococcum L. chromosome 5Aᵐ for 5A of T. aestivum and 5Sˢ of Aegilops searsii Feldman & Kislev ex K. Hammer for 5B of T. aestivum were used to produce lines that contained four copies (5Aᵐ, 5D; 5Sˢ, 5D) and six copies (5Aᵐ, 5Sˢ, 5D) of the puroindolines. There was a direct correlation in grain softness with the increase in copy number of the puroindolines. Northern blots showed increased expression of both Pina and Pinb Extraction of TX114 soluble proteins indicated that levels of both proteins were also increased. Single kernel characterization system (SKCS) analysis showed a decrease in kernel hardness by approximately 10 points below the value of 71 for ‘Chinese Spring’ (CS) for each additional copy of Pina and Pinb added. These results indicate that increasing the functional copy number of the puroindolines can impact grain softness in bread wheat.
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