Effects of Arabidopsis Ku80 deletion on the integration of the left border of T-DNA into plant chromosomal DNA via Agrobacterium tumefaciens

T-DNA integration into plant chromosomal DNA via Agrobacterium tumefaciens can be achieved by exploiting the double-strand break repair system of the host’s DNA. However, the detailed mechanism of T-DNA integration remains unclear. Here, a sequence analysis of the junction sequences of T-DNA and chromosomal DNA was performed to assess the mechanism of T-DNA integration. T-DNA was introduced into Arabidopsis wild-type and NHEJ-deficient ku80-mutant plants using the floral dip method; the junctions of the left border (LB) of T-DNA were subsequently analyzed by adapter PCR. The most frequent junction of the LB of T-DNA to chromosomal DNA (LB-to-ChrDNA) was of the filler DNA type in both lines. The lengths of direct or inverted repeat sequences within or around the filler DNA sequence were longer in the ku80 mutant. In addition, the frequency of T-DNA integration near the transcription start site was significantly higher in the ku80 mutant. Our observations suggest that the presence of the Ku80 protein affects the location of the integration of T-DNA and the pattern of the formation of repeat sequences within or around the filler DNA during LB integration into chromosomal DNA

Generating new ornamental plant varieties using ion beams

Chrysanthemum is one of the most important ornamentals for both local and international market. One of the main problems for chrysanthemum in Malaysia is the lack of new varieties to meet the ever-changing customer demands. For this purpose, mutagenesis of chrysanthemum was carried out using a combination of ion-beam irradiation and in vitro organ cultures to produce new cultivars with novel traits and wider mutation spectrum. Ray floret and nodal cultures of chrysanthemum were irradiated at various doses with 320 MeV 12C6+ ion beams. Eight mutants were selected based on their uniqueness and/or suitability for cut flower production. Among them, TIARA Red, Golden Eye, and Yellow Sun generated from Regan Red variety, and Majestic Pink from Pink variety have been filed for Plant Variety Protection (PVP) with Department of Agriculture (DOA) Malaysia