Induction of anthocyanin in the inner epidermis of red onion leaves by environmental stimuli and transient expression of transcription factors.

Novel imaging approaches have allowed measurements of the anthocyanin induction in onion epidermal cells that can be induced through water stress or transient expression of exogenous transcription factors. Environmental and genetic mechanisms that allow the normally colourless inner epidermal cells of red onion (Allium cepa) bulbs to accumulate anthocyanin were quantified by both absorbance ratios and fluorescence. We observed that water-stressing excised leaf segments induced anthocyanin formation, and fluorescence indicated that this anthocyanin was spectrally similar to the anthocyanin in the outer epidermal cells.

Evidence of inter-component recombination, intra-component recombination and reassortment in banana bunchy top virus.

Banana bunchy top virus (BBTV; family Nanoviridae, genus Babuvirus) is a multi-component, ssDNA virus, which causes widespread banana crop losses throughout tropical Africa and Australasia. We determined the full genome sequences of 12 BBTV isolates from the Kingdom of Tonga and analysed these together with previously determined BBTV sequences to show that reassortment and both inter- and intra-component recombination have all been relatively frequent occurrences during BBTV evolution. We found that whereas DNA-U3 components display evidence of complex inter- and intra-component recombination, all of the South Pacific DNA-R components have a common intra-component recombinant origin spanning the replication-associated protein gene.

Dragonfly cyclovirus, a novel single-stranded DNA virus discovered in dragonflies (Odonata: Anisoptera).

Dragonfly cyclovirus (DfCyV), a new species of ssDNA virus discovered using viral metagenomics in dragonflies (family Libellulidae) from the Kingdom of Tonga. Metagenomic sequences of DfCyV were similar to viruses of the recently proposed genus Cyclovirus within the family Circoviridae. Specific PCRs resulted in the recovery of 21 DfCyV genomes from three dragonfly species (Pantala flavescens, Tholymis tillarga and Diplacodes bipunctata).

New dynamics in an old friend: dynamic tubular vacuoles radiate through the cortical cytoplasm of red onion epidermal cells.

The textbook image of the plant vacuole sitting passively in the centre of the cell is not always correct. We observed vacuole dynamics in the epidermal cells of red onion (Allium cepa) bulbs, using confocal microscopy to detect autofluorescence from the pigment anthocyanin. The central vacuole was penetrated by highly mobile transvacuolar strands of cytoplasm, which were also visible in concurrent transmitted light images.