Variability of seed storage proteins within the sunflower gene pool

Abstract

Sunflower seeds are distinguished from those of other oil crops by the lack of antinitritive and toxic components. Besides oil they accumulate significant amounts of storage proteins called helianthinin and 2S albumins. Due to that the sunflower seeds are considered as the most promising sources of plant proteins for food industry. Moreover recent finding of the low molecular weight methionine-rich albumin SFA8 renders the sunflower seed proteins both a target for breeding improvement and a source of a valuable agronomic character for genetic modifying of other plant crops. In the present study more than 30 thousands genotypes from sunflower gene pool representing inbred lines and interline hybrids, cultivars, wild species and interspecific hybrid progenies were screened and a variation in composition of major seed proteins was demonstrated. Analysis of segregation in F₂ and BC hybrid populations has showed helianthinin genes to be clustered in three loci. Two of them co-segregated with a recombination frequency of about 22%; the third locus showed independent inheritance. In the cotyledons of F₁ hybrids between distantly related sunflower species the helianthinin protein deficient in certain polypeptides was accumulated that probably explains inviability of seeds derived from interspecific crosses in Helianthus. An allelic variation for some albumin polypeptides was also observed. N-terminal amino acid sequencing of individual albumins and analysis of segregation in the F₂ of interline hybrid allowed to suggest that the albumin gene family consists of at least three subfamilies. The level of SFA8 protein varied from trace amounts (in perennial Helianthus species) up to 30% in total albumin fraction (interline F₁ hybrid and hybrid varieties). These data indicate a breeding potential for increasing content of sulfur essential amino acids in sunflower.