Abscopal mutagenic effect of low-energy-ions in Arabidopsis Thaliana seeds

Abstract

Purpose: To demonstrate the abscopal mutagenic effect of low-energy-ion irradiation in dormant plant seeds, and its dependence on the targeted portion of seeds.

Materials and methods: Arabidopsis thaliana-lines transgenic for b-glucuronidase (GUS) recombination substrates and A. thaliana RADiation54 (AtRAD54) promoter::GUS were adopted. The seeds were irradiated from four specialised orientations with 30 KeV ⁴⁰Ar⁺ ions. The homologous recombination frequency (HRF) and the expression levels of the AtRAD54 genein non-irradiated aerial plants were measured. Moreover, several post-embryonic developments, such as growth of primary roots, differentiation of root hairs, and germination of seeds and growth of true leaves, were also analysed.

Results: It was shown that low-energy-ion irradiation of seeds led to significant increases in HRF in the non-irradiated aerial parts of irradiated plants and the aerial parts of naïve plants from irradiated progenitors. The low-energy-ion irradiation was also shown to induce an elevated expression of AtRAD54 gene in aerial plants, and to inhibit the post-embryonic developments of seeds. Moreover, the changes in HRF, expression level of the AtRAD54 gene and post-embryonic developments depended largely on the orientation of seeds with regard to low-energy-ion irradiation; and the root apical meristem (RAM)-orientated irradiation exhibited the largest effects on all biological endpoints assayed here.

Conclusions: Low-energy-ion irradiation can induce an abscopal mutagenic effect in dormant plant seeds, the extent of which depends greatly on the targeted portion of seeds.

Keywords::

• low-energy-ion irradiation
• abscopal mutagenic effect
• homologous recombination

Acknowledgements

We thank Dr Francois Belzile, Dr Seiichi Toki and NASC (Nottingham Arabidopsis Stock Center, UK) for their generous provision of the related A. thaliana seeds. We also thank Dr Zhengyan Wu, Dr Qing Huang, and Ms Kimberly Booe for their valuable discussions and careful revisions. This work is supported by the National Science Funds of China (nos. 10705029 and 10975153) and the Key Innovative Project of Chinese Academy of Sciences (no. KJCX2-YW-N34).

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Appendix

Glosssary

SAM: The source of all above-ground organs. Cells serve as stem cells to the surrounding peripheral region where they proliferate rapidly and are incorporated into differentiating leaf or flower primordia. RAM: The initial cells and tissue patterns which are established in the embryo in the case of the primary root, and in the new lateral meristems in the case of secondary roots.

Radicle: The part of a plant embryo that develops into the primary root.

Cotyledon: An embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed.

Root cap: The root cap is a section of tissue at the tip of a plant root. It is of great importance in gravity perception, protection of the growing root tip, the movement of the root through soil, and may also be involved in communication with the soil microbiota. Micropyle: The integuments, outer cell layers of the ovule enclosing the nucellus, do not enclose the nucellus completely but leave an opening at its apex referred to as the micropyle.

Vernalisation: The exposure of seeds to low temperatures to initiate or accelerate the flowering process, or, as the case with many fruit tree species, to actually break dormancy, prior to flowering. Rosette: A series of whorls of leaves or leaf-like structure produced at the base of the stem, just above the ground.

Testa: The protective outer covering of a seed, which is composed of dead cells.