DNA damage detection and transcriptional level analysis of DNA damage repair- and replication-associated genes. A and B, Typical comets for DNA damage in nuclei of flag leaves from wild type (WT; A) and cnl1 (B) at the heading stage. C, Four types of DNA damage extents in each nucleus are indicated by the units 1%, 10%, 30%, or 50%. An increased unit associated with a larger comet tail. Frequency distribution of four types of DNA damage extents in wild type and cnl1. Data are means ± sd (n = 3). Asterisks indicate significant difference by Student’s t test (**P < 0.01). D, Transcriptional level analysis of DNA repair- and replication-associated genes by RT-qPCR. Rice Ubiquitin was used as an internal control. Data are means ± sd (n = 3).