ARS | Publication request: A Puroindoline Multigene Family Exhibits Sequence Diversity in Wheat and is associated with Yield-related Traits

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 12, 2011
Publication Date: October 20, 2011
Citation: Chen, F., Zhang, F., Morris, C.F., Cui, D. 2011. A Puroindoline Multigene Family Exhibits Sequence Diversity in Wheat and is associated with Yield-related Traits. In: Gene Duplication/Book 2. ITech publishing on-line, pp. 279-288.

Interpretive Summary: Grain hardness is a leading quality characteristic of bread wheat because it dramatically influences the milling and processing properties, and determines the classification and marketing of grain. Puroindolines, composed of puroindoline a and b, are proteins and share homology with the grain softness protein (GSP), purothionins, lipid transfer proteins, and other members of the prolamin super-family of proteins. In wheat, puroindolines exist as two expressed genes, Puroindoline a and Puroindoline b, on the distal end of the short arm of chromosome 5 (5DS). An exception to this general situation lies with the tetraploid (AABB) wheats (T. turgidum), which include cultivated durum. Apparently during the allotetraploidization forming T. diccocoides, the wild ancestor of cultivated durum, both the A- and B-genome Puroindoline loci were eliminated. Consequently, hexaploid wheat possesses puroindoline a and b on the D-genome (contributed by Ae. tauschii during the allohexaploidization), but lacks homoeologous loci on the A- and B-genomes. The expression of puroindoline genes is mainly associated with ‘soft’ and ‘hard’ grain texture of bread wheat, whereas durum wheat is ‘very hard’ due to lack of puroindoline genes. This study may provide useful information to wheat breeders by MAS (Marker Assisted Selection) for improvement of grain yield.

Technical Abstract: The puroindoline genes (Pina and Pinb) are the functional components of common wheat (Triticum aestivum L.) grain hardness locus that are responsible for kernel texture. Puroindoline a and b proteins soften the endosperm of wheat kernels. In this study, a new Pinb variants Pinb-2v5 were found in durum wheat. Mapping results indicated that Pinb 2v1 is located on 7DL, Pinb 2v2 on 7BL, Pinb 2v3 on 7B, and Pinb 2v4 on 7AL. Pinb 2v4 was present in all examined common and durum wheat cultivars, and Pinb-2v1 was only present in all examined common wheat cultivars but absent in all durum wheat cultivar surveyed. Pinb 2v2 was present in small part of common and durum wheat cultivars. Pinb 2v3 was present in the most surveyed common and durum wheat cultivars and possessed at least two alleles in common and durum wheat, designated Pinb-2v3a and Pinb-2v3b. Pinb-2v5 was only found in durum wheat cultivar until now. Interestingly, Pinb-2v2 and Pinb-2v3 are possibly allelic due to their reciprocal presence in more than 300 different cultivars surveyed. Furthermore, yield-related traits of different genotypes with two kinds of combinations Pinb-A2v4/Pinb-B2v2/Pinb-D2v1 and Pinb-A2v4/Pinb-B2v3/Pinb-D2v1 were investigated in Chinese bread wheat cultivars. Results indicated that across all varieties, grain number per spike, grain weight per spike, flag leaf length and area of varieties with Pinb-B2v3 were significantly greater than those possessing Pinb-B2v2. These results possibly indicated that the Pinb-B2v3 allele was associated with preferable grain yield traits compared to the Pinb-B2v2 allele in bread wheat. Study of puroindoline b-2 gene polymorphism in common and durum wheat germplasm could provide useful information for further understanding molecular and genetic basis of kernel hardness and illustrating gene duplication events in wheat. In addition, this study also provides useful information for better understanding the molecular and genetic basis of wheat grain yield.