The Accumulation of Oleosins Determines the Size of Seed Oilbodies inArabidopsis

Abstract

We investigated the role of the oilbody proteins in developing and germinating Arabidopsis thaliana seeds. Seed oilbodies are simple organelles comprising a matrix of triacylglycerol surrounded by a phospholipid monolayer embedded and covered with unique proteins called oleosins. Indirect observations have suggested that oleosins maintain oilbodies as small single units preventing their coalescence during seed desiccation. To understand the role of oleosins during seed development or germination, we created lines of Arabidopsis in which a major oleosin is ablated or severely attenuated. This was achieved using RNA interference techniques and through the use of a T-DNA insertional event, which appears to interrupt the major (18 kD) seed oleosin gene of Arabidopsis and results in ablation of expression. Oleosin suppression resulted in an aberrant phenotype of embryo cells that contain unusually large oilbodies that are not normally observed in seeds. Changes in the size of oilbodies caused disruption of storage organelles, altering accumulation of lipids and proteins and causing delay in germination. The aberrant phenotypes were reversed by reintroducing a recombinant oleosin. Based on this direct evidence, we have shown that oleosins are important proteins in seed tissue for controlling oilbody structure and lipid accumulation.

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

“…Most of the oil bodies in Arabidopsis seedlings disappeared within 6 d after germination on 60 mM N (Siloto et al, 2006). Oil drops in seedlings often correlate with the inhibition of stored lipid breakdown.…”

Spatiotemporal Seed Development Analysis Provides Insight into Primary Dormancy Induction and Evolution of theLepidium DELAY OF GERMINATION1Genes

“…2 and 7), we captured in type I infructescences stages prior to and at the onset of seed germinability until full premature germination (prior to dormancy induction), and in types II and III infructescences we captured all stages prior to, during, and after the induction of primary dormancy, including the full premature germination stage. To assign these stages to events during seed development and maturation on the molecular level, we analyzed the expression patterns of well-known marker proteins including oleosin (seed storage accumulation), EM6 (seed maturation), and dehydrin (desiccation tolerance; Close et al, 1993;Huang, 1996;Bies et al, 1998;Crowe et al, 2000;Ruuska et al, 2002;Boudet et al, 2006;Siloto et al, 2006;Leprince and Buitink, 2010). Oleosin accumulation during L. papillosum seed development was enhanced with the onset of premature germinability and early maturation in type I and II infructescences.…”

“…kD indicates the protein molecular mass marker ladder. [See online article for color version of this figure.] assign these protein patterns of LepaDOG1 expression to developmental stages within the L. papillosum infructescence, we used monoclonal antibodies directed against oleosin and polyclonal antibodies against EM6 (for Early Met labeled) and dehydrin; the expression abundance of these three proteins is indicative for seed storage accumulation, maturation, and the induction of desiccation tolerance, respectively (Close et al, 1993;Crowe et al, 2000;Boudet et al, 2006;Siloto et al, 2006). In support of the finding that LepaDOG1 is already abundant in immature FOs, abundant LepaDOG1 expression preceded oleosin expression and, therefore, occurs early during seed development already at the filling stage (Fig.…”

“…For immunological detection, the following primary antibodies were used: two different polyclonal antibodies, a-DOG1 1 (Schwab, 2008) and a-DOG1 2 , directed against AtDOG1; a monoclonal antibody, a-oleosine, directed against Arabidopsis D9 oleosin (Crowe et al, 2000;Siloto et al, 2006); a polyclonal antibody, a-EM6, directed against Medicago truncatula Em6 (Boudet et al, 2006); and a polyclonal antibody, a-dehydrin, directed against a wide range of plant species dehydrins (Close et al, 1993). Anti-rabbit IgG-peroxidase conjugate (Sigma) was used for the detection of a-DOG1 1 , a-DOG1 2 , a-EM6, and a-dehydrin, and anti-mouse…”

Proteomic Analysis of Near-Isogenic Sunflower Varieties Differing in Seed Oil Traits

“…1 This wide variation is in part due to anatomical and morphological differences, particularly with respect to seed coat, embryo, and endosperm contribution to overall seed structure. 2,3 Differences in metabolic regulation leading up to and including de novo fatty acid synthesis, 4,5 as well as structural packaging of storage triacylglycerol, 6 may also contribute to this wide variation. However, these differences can be difficult to unveil amidst a background of evolutionarilydivergent traits including embryo size.…”