Identification of allelic variations of puroindoline genes controlling grain hardness in wheat using a modified denaturing PAGE

Abstract

Puroindoline genes (Pina and Pinb) form the molecular basis of wheat grain hardness or texture. Variations in either gene are reported to be associated with grain hardness in wheat. Here, a modified denaturing PAGE was used to detect Pina and Pinb allelic variations in 102 common wheat cultivars and other species related to wheat. Two variations of Pina (Pina-D1b and Pina-D1p) and five variations of Pinb (null, Pinb-D1b, PinbD1u, Pinb-D1v and Pinb-D1w) were identified in common (T. aestivum) and spelt wheats (T. aestivum ssp. spelta). No allelic variation was found in Tibet semi-wild wheat (T. aestivum ssp. tibetanum), club wheat (T. compactum), or Aegilops tauschii. Puroindoline genes were absent in wild emmer (T. turgidum var. dicoccoides). The sequencing results of the PCR fragments from Pina and Pinb (except for null type) indicated allelic variants carrying single base mutation, such as Pina-D1p, Pinb-D1u, Pinb-D1v and Pinb-D1w were novel types. Our results showed that the modified PAGE used in this study provided a satisfactory resolving power for identifying single nucleotide mutations; therefore, it is a practical and simple tool to study allelic variation of Pina and Pinb in wheat and related species.

The determinants of grain texture in cereals

“…The kernels of the null mutants, lacking either PINA or PINB, are harder than those with single base substitutions, able to produce some of the proteins (Giroux et al 2000;Martin et al 2001;Cane et al 2004;Clarke and Rahman 2005;Chang et al 2006). This data is in agreement with the expression of the genes measured by RT-PCR.…”

“…These mutations mainly occur in Chinese wheat germplasm (cultivars, landraces and endemic wheats) and differ from those of the other countries because China is the secondary centre of wheat origin with a broad diversity in the germplasm. In addition, two substitution mutations, Pinb-D1t (Chen et al 2006) and Pinb-D1v (Chang et al 2006) were recently reported in this germplasm.…”

“…Pinb-D1e and Pinb-D1g, which are like Pinb-D1f null mutations because of the one point substitution to the stop codon (positions 39 and 56 respectively), were found in the same American historical wheats (Morris et al 2001b). Other Pinb-D1 null mutations, Pinb-D1h and Pinb-D1i (Ikeda et al 2005), Pinb-D1p , Pinb-D1r and Pinb-D1s (Ram et al 2005), and Pinb-D1u (Chang et al 2006;Chen et al 2007) are of the frame shift type (Table 2). Pinb-D1u has a different effect on grain hardness in different cultivars (hard or mixed grain texture).…”

“…Chang et al (2006) proposed the amplification of the whole coding sequence. Sequencing the amplified PCR fragments identified allelic variants corresponding to single gene mutations.…”

Chromosomes 3B and 4D are associated with several milling and baking quality traits in a soft white spring wheat (Triticum aestivum L.) population

“…Thus, the identified QTL are for grain texture traits that are distinct from these known mutations and potentially of more use to wheat breeders since they rarely make crosses outside of texture classes. Chang et al (2006) found that several loci for storage protein content were associated with kernel hardness on chromosome 2B. Chang et al (2006) concluded that other factors such as pentosans, polar lipids, and protein in the endosperm may also affect kernel texture.…”