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Genes encoding subunits of the mitochondrial ribosomal protein complex are distributed between the mitochondrial and nuclear genomes. In Arabidopsis thaliana only seven out of the nearly 70 genes coding for mitochondrial ribosomal subunit proteins are present in the mitochondrial genome. Nevertheless, these genes are co-ordinately expressed. Here, we present the first report of characterization of promoter of a plant mitochondrial ribosomal protein gene AtRps19 (At5g47320), a single copy nuclear gene in A. thaliana. Analysis of transgenic A. thaliana plants carrying seven different AtRps19 upstream fragments linked to the uidA reporter gene revealed that the 879 bp fragment containing the 5′ UTR and the intergenic region is capable of driving gene expression in most of the vegetative tissues. However, inclusion of 447 bp of the upstream gene sequences was essential for obtaining full expression in all tissues including anthers and pollen. Thus, we provide the first experimental proof of overlapping genes in plants. qRT-PCR analysis showed that uidA and native AtRps19 transcript levels were comparable in plants carrying the D4 (−676/+650) construct, indicating that the 1326 bp D4 fragment represents the native promoter of the AtRps19 gene. Comparison of AtRps19 promoter with the widely used CaMV35S promoter showed that AtRps19 promoter is capable of driving gene expression in all tissues including anthers and pollen but was less efficient than the CaMV35S promoter.

Seed size is a highly heritable trait in mustard and increasing seed size could improve crop productivity. Here we report the effect of overexpression of two Arabidopsis genes SHB1 and KLUH on seed weight and other yield contributing traits in Brassica juncea. KLUH gene was expressed under its own promoter, whereas the constitutive HPL promoter drove SHB1. Transgenic status was confirmed through PCR, RT-PCR and Southern analyses. The three SHB1 events contained single copy of transgene, whereas 12 KLUH events carried 1–4 copies of transgenes. All transgenics were fertile and comparable to non-transgenic counterpart for most of the agronomic traits in both T0 and T1 generations. Seed size and seed weight in SHB1 transgenics were 30–40% higher than the control, whereas one KLUH event showed significant increase in seed weight. Constitutive overexpression of SHB1 in B. juncea had undesirable pleiotropic effects that were comparable to the Arabidopsis lines overexpressing IKU2.