Differential, temporal and spatial expression of genes involved in storage oil and oleosin accumulation in developing rapeseed embryos: implications for the role of oleosins and the mechanisms of oil-body formation

Abstract

The temporal and spatial expression of oleosin and delta 9-stearoyl-ACP desaturase genes and their products has been examined in developing embryos of rapeseed, Brassica napus L. var. Topas. Expression of oleosin and stearate desaturase genes was measured by in situ hybridisation at five different stages of development ranging from the torpedo stage to a mature-desiccating embryo. The temporal pattern of gene expression varied dramatically between the two classes of gene. Stearate desaturase gene expression was relatively high, even at the torpedo stage, whereas oleosin gene expression was barely detectable at this stage. By the stage of maximum embryo fresh weight, stearate desaturase gene expression had declined considerably while oleosin gene expression was at its height. In contrast to their differential temporal expression, the in situ labelling of both classes of embryo-specific gene showed similar, relatively uniform patterns of spatial expression throughout the embryo sections. Immunogold labelling of ultra-thin sections from radicle tissue with anti-oleosin antibodies showed similar patterns to sections from cotyledon tissue. However, whereas at least three oleosin isoforms were detectable on western blots of homogenates from cotyledons, only one isoform was found in radicles. This suggests that some of the oleosin isoforms may be expressed differentially in the various types of embryo tissue. The differential timing of stearate desaturase and oleosin gene expression was mirrored by similar differences in the timing of the accumulation of their ultimate products, i.e. storage oil and oleosin proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

The Accumulation of Oleosins Determines the Size of Seed Oilbodies inArabidopsis

“…It has been speculated that oleosins stabilize oilbodies preventing coalescence of the lipid particles during seed dehydration (Cummins et al, 1993). Some authors have also suggested that oleosins prevent oilbodies from coalescing during seed imbibition and germination (Leprince et al, 1998).…”

Integral Proteins in Plant Oil Bodies

“…Targeting of oil-body proteins, particularly oleosin, has been extensively investigated via in vivo systems using transgenic techniques and in vitro systems using microsomal membranes for integration of translated proteins [107][108][109][110][111]. The signal segment for specific targeting of oleosin to oil bodies is apparently located within the protein itself since recombinant oleosins are able to target correctly oil bodies in different transgenic plants and yeasts [112][113][114].…”

Small RNA Profiling in Two Brassica napus Cultivars Identifies MicroRNAs with Oil Production- and Development-Correlated Expression and New Small RNA Classes

“…The oil accumulation of B. napus seeds usually starts around 3 weeks after flowering and peaks after another 3 weeks (Norton and Harris, 1975;Cummins et al, 1993;Eastmond and Rawsthorne, 2000). The seed oil content varies significantly among B. napus cultivars or under different growth environments.…”