Recently, a study published in Radiation Research has revealed the modulation of bystander DNA repair potential by targeted tissue volume in Arabidopsis thaliana. This work was performed by Prof. BIAN Po and his colleagues in our Institute.

Radiation-induced bystander effects (RIBE) entail cascade of bystander signals produced by the hit cells to the neighboring cells to regulate various biological processes including DNA damage repair. In RIBE, the targeted volume, or the number of irradiated cells, is one of the important factors that determine the quantity of bystander signals and the magnitude of response to radiation in cell system. However, there is no direct evidence yet to clarify whether radiation-targeted volume can modulate bystander DNA repair potential.

In BIAN’s study, the aerial part (AP) and/or upper parts of primary root (UR) of A. thaliana seedlings were locally irradiated with X-rays and the DNA repair potential of root tip cells was assessed using the Radio-adaptive response (RAR).

They found that X-ray irradiation of the aerial parts (AP) of A. thaliana seedlings (5 Gy) initiated RAR in the root-tip cells, which exhibited an alleviated repression of root growth and root cell division, and reduced amount of DNA strand breaks.

 
Time course of expression of DNA damage repair gene suggested the increased DNA repair potential in bystander root tip cells by X-ray irradiation of the aerial parts.

However, the X-ray-targeted volume was enlarged to contain aerial part and upper roots, the bystander DNA repair potential was reduced by selectively disturbing the transport of bystander signals responsible for HR repair.

This work challenged the canonical view about the positive correlation between the targeted volume and bystander effect, and may provide a new information for the radiation induced bystander effects.

This work was supported by the grants from National Natural Science Foundation of China, the Youth Innovation Promotion Association of Chinese Academy of Sciences.

Link of the paper: Negative Modulation of Bystander DNA Repair Potential by X-Ray Targeted Tissue Volume in Arabidopsis thaliana

The Negative modulation of Bystander DNA Repair Potential by X-ray-Targeted Tissue Volume in Arabidopsis thaliana. A) Schematic representation of local X-ray irradiation of 6 d-old seedlings; B) Induction of RAR for root growth by X-ray irradiation of AP of seedlings; C) Reduced bystander DNA repair potential by X-ray irradiation of AP + UR of seedlings; D) Effect of priming X-irradiation of AP and AP + UR on the time-course of transcription of DNA repair genes in root tips after subsequent CR; E) Schematic representation of the influence of X-irradiation of UR on the root transport of bystander signal to root tip.（Image by WANG Ting）