wrinkled1: A Novel, Low-Seed-Oil Mutant of Arabidopsis with a Deficiency in the Seed-Specific Regulation of Carbohydrate Metabolism1

Abstract

During oil deposition in developing seeds of Arabidopsis, photosynthate is imported in the form of carbohydrates into the embryo and converted to triacylglycerols. To identify genes essential for this process and to investigate the molecular basis for the developmental regulation of oil accumulation, mutants producing wrinkled, incompletely filled seeds were isolated. A novel mutant locus, wrinkled1 (wri1), which maps to the bottom of chromosome 3 and causes an 80% reduction in seed oil content, was identified. Wildtype and homozygous wri1 mutant plantlets or mature plants were indistinguishable. However, developing homozygous wri1 seeds were impaired in the incorporation of sucrose and glucose into triacylglycerols, but incorporated pyruvate and acetate at an increased rate. Because the activities of several glycolytic enzymes, in particular hexokinase and pyrophosphate-dependent phosphofructokinase, are reduced in developing homozygous wri1 seeds, it is suggested that WRI1 is involved in the developmental regulation of carbohydrate metabolism during seed filling.

Probing in Vivo Metabolism by Stable Isotope Labeling of Storage Lipids and Proteins in Developing Brassica napusEmbryos

“…This result also emphasizes the independence of protein and oil biosynthesis and may in part explain why decreasing the amount of protein or oil in seeds of Arabidopsis mutants does not generally lead to a balancing increase in the other major storage component. For example, in Arabidopsis abi/aba mutants (Finkelstein and Somerville, 1990), storage protein content is strongly reduced but oil content does not change significantly, and in the wri1 mutant (Focks and Benning, 1998), oil is reduced 80% but storage protein content remains similar to wild-type seeds.…”

Alterations in Seed Development Gene Expression Affect Size and Oil Content of Arabidopsis Seeds

“…This increase in the degree of desaturation by an enhanced conversion of 18:2 to 18:3 has previously been observed in Arabidopsis mutants affected in seed oil deposition. It can be explained by the reduction in the pool size of fatty acids available for desaturases in the mutants resulting in an enhanced conversion to the unsaturated fatty acids (Focks and Benning, 1998;Moreno-Pérez et al, 2012).…”

“…Suc is known to be imported into the embryo and to represent the main source for acetyl-CoA production and oil biosynthesis in the seed (Baud et al, 2005). The amount of Suc in mature Arabidopsis wild-type seeds is around 0.5 mg per seed (Focks and Benning, 1998;Baud et al, 2002;Fig. 2C).…”

“…TAG and proteins are the most abundant forms for carbon deposition in Arabidopsis seeds (Focks and Benning, 1998). Total fatty acids were quantified in the mutant seeds by gas chromatography (GC) of methyl esters as a measure for the content of storage oil.…”

“…The outermost layer of the seed is the seed coat, which is of maternal origin and is derived from the inner and outer integument cells (Haughn and Chaudhury, 2005). Embryo proliferation in the second phase is accompanied with accumulation of the seed storage compounds, in particular of proteins and triacylglycerol (TAG), which are crucial to nourish the seedling before the onset of photosynthesis (Focks and Benning, 1998). The seed accumulates large amounts of starch in the early phase but this starch is later degraded.…”