Developmental and environmental effects on the assembly of glutenin polymers and the impact on grain quality of wheat

Abstract

Wheat kernel development can be divided into three phases i.e. cell division, cell enlargement and dehydration. Accumulation of gluten proteins continues till the end of the cell enlargement phase. During the dehydration phase, post-translational polymerization of the glutenin subunits occurs to form very large glutenin polymers. Assembly of the glutenin polymers has been monitored by increase in the unextractable polymeric protein. Lines possessing HMW-GS related to dough strength (e.g. 5+10) started accumulating large polymers several days earlier than lines with HMW-GS related to dough weakness (e.g. 2+12) and maintained their higher amounts till maturity. This may be explained by faster polymerization resulting from a higher concentration of cysteine residues in the x-type HMW-GS. Sulphur deficiency leads to an increase in the ratio of HMW- to LMW-GS, causing a shift in the MWD to higher MWs, resulting in bucky dough properties. High temperature during grain development appears to shift the MWD to lower MWs with corresponding lowering of dough strength but the presence of strength-associated HMW-GS appears to confer greater tolerance to heat stress. Since sulphur deficiency and higher global temperatures may be expected to increase in the future, some suggestions how breeders may use strategies to counter these effects are put forward.