Genetic control of sterol esterification in developing wheat endosperm

Abstract

Summary1. The action of gene Pin, previously characterized by the sterol ester patterns of mature whole wheat kernels, has been found to be restricted to the endosperm and not to affect the embryo, the pericarp or the seed coat.2. The dominant alíele Pin, which determines a sterol ester pattern with palmitate as the main ester, is also responsible for a low level of free sterol at maturity. A high level of free sterol is associated with the recessive alíele pin, which determines an ester pattern with linoleate as the main ester.3. Divergence between the two phenotypes starts at about 21 days after anthesis, when cell proliferation has been completed, the aleurone layer has differentiated, and only cell enlargement is taking place. A marked increase in esterification, mainly by palmitate, which is controlled by the dominant alíele, is concomitant with a sharp decrease in free sterol.4. The increased net esterification is non-specific with respect to 4-demethyl sterols, because it affects the four main ones, namely sitosterol, stigmasterol, campesterol and cholesterol.

Endosperm sterol phenotype and germination in wheat

“…Our present and previous results [4,5] suggest that endosperm is not involved in supplying sterols to the growing tissues during germination and that, on the other hand, enough sterols are accumulated as esters in the embryo during development to serve that purpose.…”

“…The rapid decline of scutellum sterols is concomitant with, and of the same order as, their increase in coleoptile and roots. Most of the mature embryo sterols are esterified and we have previously shown that about 2/3 of these esters are synthesized just prior to maturity, when seeds are starting to dry [5]. These facts suggest a storage role for the embryo sterol esters.…”

“…We have previously described two genetic variants of the free and conjugated sterol profile in wheat endosperm [1][2][3][4][5]. One phenotype, designated PL, is characterized by a low proportion of free sterol and a high proportion of steryl palmitate, whereas in the other, L, free sterol is the predominant form.…”

“…One phenotype, designated PL, is characterized by a low proportion of free sterol and a high proportion of steryl palmitate, whereas in the other, L, free sterol is the predominant form. This difference is controlled by allelic forms of a single gene, designated Pin [5]. Research reported here deals with the possible influence of endosperm sterol phenotype on sterol metabolism and development rate of the germinating axis.…”