Regulation of Ku gene promoters in Arabidopsis by hormones and stress

The Ku70/Ku80 heterodimer plays a crucial role in non-homologous end-joining during DNA repair, and is also involved in multiple cellular processes such as telomere maintenance, transcription, and apoptosis. In this study, we investigate the regulation of AtKu genes in higher plants. Promoters of the AtKu70 and AtKu80 were isolated from Arabidopsis and their activities characterised using GUS reporter constructs. AtKu promoter activities were relatively higher in hypocotyls and cotyledons upon germination and in stigma and siliques as well at their early developing stages. Furthermore, AtKu promoter activities could be enhanced by gibberellic acid, auxins, and jasmonic acid, but repressed by abscisic acid, salicylic acid, heat, drought and cold, respectively. Deletion analysis demonstrates minimal lengths of ~400 bp and 600 bp upstream of transcription start site for functional promoters of AtKu70 and AtKu80, respectively. Taken together, expressions of Ku genes are regulated both by developmental programs as well as by plant hormones and environmental stresses.

Genetic influences on the split seed disorder in Lupinus angustifolius L.

During an investigation of the disorder known as split seed in narrow-leafed lupins (L. angustifolius) studies were made on an F2 population from a cross between the 'bitter' cultivar New Zealand Blue and the 'sweet' cultivar Uniwhite. In a situation where the split seed problem occurred, the presence of the gene for low alkaloid (iucundus) in the homozygous state lowered the proportion of normal seeds from 78.5 to 10.9%, and the non-shedding phenotypes (tardus), in the absence of iucundus, showed reduction of normal seed from 81.8% to 62.4%. Additional experiments with a wider range of genotypes verified the invoivement of the iucundus gene and showed that the Ku gene for earlier flowering could provide a degree of escape from the disorder. The split seed relationship with iucundus and tardus showed differences in expression at one site, which indicated a difference in their mechanism of action at least in the production of severely deformed or shrivelled seed.