Cruciferin gene families are expressed coordinately but with tissue-specific differences during Brassica napus seed development

Abstract

The major storage protein in seeds of Brassica napus, the 12S globulin cruciferin, is composed of three different groups of subunits; cru1, cru2/3 and cru4. By using gene family-specific probes, we have investigated the accumulation, rate of synthesis and spatial distribution of transcripts corresponding to the different groups of cruciferin subunits in developing seeds. Cruciferin transcripts derived from different gene families accumulate coordinately to comparable amounts during seed development. The corresponding gene families are, however, transcribed at different rates. Investigation of the spatial distribution of transcripts corresponding to each group of cruciferin subunits in the developing seed by in situ hybridization, revealed that mRNAs of all three types accumulate in both axis and cotyledons. Transcripts derived from cru1 and cru4 gene families show a similar cell specificity and accumulate in a similar spatial manner during seed development. In contrast, mRNAs corresponding to the cru2/3 gene family are expressed with a partly different cell specificity and show a slightly different pattern of accumulation in the axis and cotyledons, with a delayed accumulation in epidermal cells. In the cotyledons, the initial accumulation of this type of cruciferin mRNAs is also distinguished from the two other types. The differences in cell specificity are seen in the root cap and in provascular cells, where mRNAs belonging to the cru2/3 family are absent.

Fluorescent labelling of nascent RNA reveals nuclear transcription domains throughout plant cell nuclei

“…The protocol for BrUTP incorporation was according to Wansink et al (1993), adapted for plant nuclei with the transcription buffer according to Sj6dahl et al (1993). A drop of HG-buffer containing isolated nuclei was put on an aminopropyl-triethoxysilane-coated slide (Sigma Chemical Co., St. Louis, MO, U.S.A.).…”

“…In plants, less is known about the structural organization of RNA processing. Recently, Sj6dahl et al (1993) have incorporated 32p-UTP into nascent RNA of isolated nuclei of Brassica napus seeds in order to identify the synthesis of transcripts belonging to three cruciferin gene families. This, however, does not allow a precise localization of the sites of transcription because of the long path-length of the ~-radiation.…”

Transporters for nitrogenous compounds in plants

“…Synthesis of specific storage proteins are induced during the development of seeds or vegetative storage organs such as tubers [36,95]. The pattern of storage protein expression is best analysed in Brassicaceae [21,76,112]. In Arabidopsis, which has only a minor endosperm, nitrogen is mainly stored as 2S and 12S storage proteins in the cotyledons of the embryo.…”

Phosphorylation of the 12 S globulin cruciferin in wild-type and abi1-1 mutant Arabidopsis thaliana (thale cress) seeds

“…Temporal and spatial factors influence the accumulation of seed storage proteins in the cotyledon and axis during seed development [10][11][12]. The latter is exemplified by the observation that antisense suppression of napin expression causes a corresponding increase in cruciferin synthesis, thus neutralizing the overall impact on total seed protein content [13].…”