Cytological events in explants of Arabidopsis thaliana during early callogenesis

Nuclear genome stability in long-term cultivated callus lines of Fagopyrum tataricum (L.) Gaertn

Long-term cultivated Fagopyrum tataricum (L.) Gaertn. (Tartary buckwheat) morphogenic and non-morphogenic callus lines are interesting systems for gaining a better understanding of the mechanisms that are responsible for the genetic stability and instability of a plant tissue culture. In this work, we used histological sections and transmission electron microscopy to identify and describe the morphology of the nuclei of all of the analysed callus lines. We demonstrated that the embryogenic callus cells had prominent round nuclei that did not contain heterochromatin clumps in contrast to the non-morphogenic callus lines, in which we found nuclei that had multiple lobes. Flow cytometry analysis revealed significant differences in the relative DNA content between the analysed calli. All of the analysed morphogenic callus lines had peaks from 2C to 8C as compared to the non-morphogenic callus lines, whose peaks did not reflect any regular DNA content and exceeded 8C and 16C for the line 6p1 and 16C and 32C for the callus line 10p2A. The results showed that non-morphogenic calli are of an aneuploid nature. The TUNEL test enabled us to visualise the nuclei that had DNA fragmentation in both the morphogenic and non-morphogenic lines. We revealed significantly higher frequencies of positively labelled nuclei in the non-morphogenic lines than in the morphogenic lines. In the case of the morphogenic lines, the highest observed frequency of TUNEL-positive nuclei was 7.7% for lines 2-3. In the non-morphogenic calli, the highest level of DNA damage (68.5%) was revealed in line 6p1. These results clearly indicate greater genome stability in the morphogenic lines.

Watching the grin fade: tracing the effects of polyploidy on different evolutionary time scales

Polyploidy, or whole-genome duplication (WGD), is a recurrent mutation both in cell lineages and over evolutionary time. By globally changing the relationship between gene copy number and other cellular entities, it can induce dramatic changes at the cellular and phenotypic level. Perhaps surprisingly, then, the insights that these events can bring to understanding other cellular features are not as well appreciated as they could be. In this review, we draw on examples of polyploidy from animals, plants and yeast to explore how investigations of polyploid cells have improved our understanding of the cell cycle, biological network complexity, metabolic phenotypes and tumor biology. We argue that the study of polyploidy across organisms, cell types, and time scales serves not only as a window into basic cell biology, but also as a basis for a predictive biology with applications ranging from crop improvement to treating cancer.

Variations in BARE-1 insertion patterns in barley callus cultures

The stability of aging barley calli was investigated with the barley retroelement 1 (BARE-1) retrotransposon specific inter-retrotransposon amplified polymorphism (IRAP) technique. Mature embryos of barley (Hordeum vulgare cv. Zafer-160) were cultured on callus induction MS medium supplemented with 3 mg/L 2,4-D and maintained on the same medium for 60 days. Ten IRAP primers were used in 25 different combinations. The similarity index between 30-day-old and 45-day-old calli was 84%; however, the similarity index between mature embryos and 45-day-old calli was 75%. These culture conditions caused BARE-1 retrotransposon alterations to appear as different band profiles. This is the first report of the use of the IRAP technique in barley in an investigation of callus development.