Altered seed oil and glucosinolate levels in transgenic plants overexpressing the Brassica napus SHOOTMERISTEMLESS gene

Abstract

SHOOTMERISTEMLESS (STM) is a homeobox gene conserved among plant species which is required for the formation and maintenance of the shoot meristem by suppressing differentiation and maintaining an undetermined cell fate within the apical pole. To assess further the role of this gene during seed storage accumulation, transgenic Brassica napus (Bn) plants overexpressing or down-regulating BnSTM under the control of the 35S promoter were generated. Overexpression of BnSTM increased seed oil content without affecting the protein and sucrose level. These changes were accompanied by the induction of genes encoding several transcription factors promoting fatty acid (FA) synthesis: LEAFY COTYLEDON1 (BnLEC1), BnLEC2, and WRINKLE1 (BnWRI1). In addition, expression of key representative enzymes involved in sucrose metabolism, glycolysis, and FA biosynthesis was up-regulated in developing seeds ectopically expressing BnSTM. These distinctive expression patterns support the view of an increased carbon flux to the FA biosynthetic pathway in developing transformed seeds. The overexpression of BnSTM also resulted in a desirable reduction of seed glucosinolate (GLS) levels ascribed to a transcriptional repression of key enzymes participating in the GLS biosynthetic pathway, and possibly to the differential utilization of common precursors for GLS and indole-3-acetic acid synthesis. No changes in oil and GLS levels were observed in lines down-regulating BnSTM. Taken together, these findings provide evidence for a novel function for BnSTM in promoting desirable changes in seed oil and GLS levels when overexpressed in B. napus plants, and demonstrate that this gene can be used as a target for genetic improvement of oilseed species.

Altered Fruit and Seed Development of Transgenic Rapeseed (Brassica napus) Over-Expressing MicroRNA394

“…Seeds of Brassicaceae family such as Brassica napus accumulate lipids mainly in the form of triacylglycerols as the major source of energy required for seed germination and post-germination growth. Although genetic screens and molecular identification have allowed for characterization of a number of genes related to seed development, oil production and biosynthesis of fatty acids in both Arabidopsis and Brassica napus [ 4 , 5 , 10 , 36 – 38 ], investigations on miRNAs involved in the fruit and seed development with regard to oil metabolism are lacking. Our results have shown that miR394 was expressed in flower buds, with a low abundance at the latter stage of seed development; in contrast, expression of LCR was relatively higher during the seed maturation.…”

Cytosolic Phosphorylating Glyceraldehyde-3-Phosphate Dehydrogenases Affect Arabidopsis Cellular Metabolism and Promote Seed Oil Accumulation

“…Glycolysis is a significant source of ATP, NADH, and NADPH for protein and oil biosynthesis, which are energetically costly processes, in seeds and transgenic alterations impact the levels of energy metabolites as well as storage reserve production (Vigeolas et al, 2004;Elhiti et al, 2012). The levels of ATP, ADP, NAD(P), and NAD(P)H were determined and their ratios calculated as a proxy for energy charge and reducing power in wildtype and transgenic lines.…”

Structural and functional alterations in photosynthetic apparatus of plants under cadmium stress

“…Chloroplast structure disturbance has been partly manifested by a notable decrease in chloroplast number and size, grana stacking, starch grain content and accumulation of plastoglobuli observed in various plants such as Picris divarticata (75 μM, 14 days after treatment (DAT)), Hordeum vulgare (5 μM, 15 DAT) and Brassica (Ying et al 2010; Wang et al 2011; Elhiti et al 2012). Further, plants show differential aggregation of grana in young and older leaves.…”