Factors Affecting the Radiosensitivity of Hexaploid Wheat to γ-Irradiation: Radiosensitivity of Hexaploid Wheat (<i>Triticum aestivum</i> L.)

<div><p>Understanding the radiosensitivity of plants, an important factor in crop mutation breeding programs, requires a thorough investigation of the factors that contribute to this trait. In this study, we used the highly radiosensitive wheat (<i>Triticum aestivum</i> L.) variety HY1 and J411, a γ-irradiation-insensitive control, which were screened from a natural population, to examine the factors affecting radiosensitivity, including free radical content and total antioxidant capacity, as well as the expression of <i>TaKu70</i> and <i>TaKu80</i> (DNA repair-related genes) as measured by real-time PCR. We also investigated the alternative splicing of this gene in the wild-type wheat ecotype by sequence analysis. Free radical contents and total antioxidant capacity significantly increased upon exposure of HY1 wheat to γ-irradiation in a dose-dependent manner. By contrast, in J411, the free radical contents exhibited a similar trend, but the total antioxidant capacity exhibited a downward trend upon increasing γ-irradiation. Additionally, we detected dose-dependent increases in <i>TaKu70</i> and <i>TaKu80</i> expression levels in γ-irradiated HY1, while in J411, <i>TaKu70</i> expression levels increased, followed by a decline. We also detected alternative splicing of <i>TaKu70</i> mRNA, namely, intron retention, in HY1 but not in J411. Our findings indicate that γ-irradiation induces oxidative stress and DNA damage in hexaploid wheat, resulting in growth retardation of seedlings, and they suggest that <i>TaKu70</i> may play a causal role in radiosensitivity in HY1. Further studies are required to exploit these factors to improve radiosensitivity in other wheat varieties.</p></div

Effect of gamma irradiation on DNA repair-related genes <i>TaKu70</i> and <i>TaKu80 and plant phenotypes</i>.

<p>(A, B) Photographs of HY1 and J411 plants under different dosages of γ-irradiation. Seedling height and root length decreased significantly with increasing gamma irradiation dosage more quickly in HY1 than in J411. (C, D) Histogram analysis of variation rate of root length and seedling height in HY1 and J411. The X-axis represents the treatment dosage, including 0 Gy, 100 Gy, 150 Gy and 250 Gy. The Y-axis represents the variation rate of root length and seedling in HY1 and J411. Significant differences were analyzed by spass 16.0 (P < 0.05) (E, F)The X-axis represents the treatment dosage, including 0 Gy, 100 Gy, 150 Gy and 250 Gy. The Y-axis represents <i>Taku70</i> gene expression level. Dark gray bars indicate <i>Taku70</i> and <i>Taku80</i> gene expression values in HY1, and light gray bars indicate those in J411. Significant differences between treatment groups and the control groups in the HY1and J411 variety were analyzed by spass 16.0 (P < 0.05).</p

The effect of intron retention on the encoded protein.

<p><i>TaKu70</i> encodes a 626 amino acid protein. Gray highlighting represents the protein encoded by the mRNA harboring intron retention in HY1.</p

Effect of gamma irradiation on free radical levels.

<p>The X-axis represents the treatment dosage, including 0 Gy, 100 Gy, 150 Gy and 250 Gy. The Y-axis represents the free radical levels. Dark gray bars indicate free radical contents in HY1, light gray bars represent free radical contents in the J411 variety. Significant differences between treatment groups and the control groups in the HY1and J411 variety were analyzed by spass 16.0 (P < 0.05).</p

Effect of gamma irradiation on T-AOC in HY1 and J411 wheat.

<p>The X-axis represents the treatment dosage, including 0 Gy, 100 Gy, 150 Gy and 250 Gy. The Y-axis represents T-AOC levels. Dark gray bars represent T-AOC values in HY1, and light gray bars represent those in J411. Significant differences between treatment groups and the control groups in the HY1and J411 variety were analyzed by spass 16.0 (P < 0.05).</p

Heat map analysis of all data.

<p>The abscissa represents free radical levels, A-TOC levels, seedling height, root length, <i>TaKu70</i> and <i>TaKu80</i> expression levels. The ordinate represents different dosages of γ-irradiation. The primary data were LOG₂ transformed using Heml1.0 software. The color variation represents different values.</p

The top 20 significantly enriched pathways identified by KEGG analysis.

<p>The top 20 significantly enriched pathways identified by KEGG analysis.</p

DEGs and TFs involved in chloroplast development, and chlorophyll biosynthesis in <i>mta</i> transcriptome.

<p>DEGs and TFs involved in chloroplast development, and chlorophyll biosynthesis in <i>mta</i> transcriptome.</p

Quantitative real-time PCR analysis of 13 DEP-coding genes.

<p>The relative gene expression levels of selected target genes were normalized to a BestKeeper composed of the endogenous reference gene <i>TaActin</i>. (A) The black and gray bars represent WT and <i>mta</i>, respectively. Low values indicate down-regulation in <i>mta</i>, while high values indicate up-regulation. (B) The different colors represent 12 DEGs, including <i>PsbO</i> (1–3), <i>PsbP</i> (4–8), <i>Lhca1</i> (9–12). Positive values indicate higher expression in <i>mta</i> and negative values denote higher expression in WT. Error bars represent the standard deviation.</p