Isolation of a novel UVB-tolerant rice mutant obtained by exposure to carbon-ion beams

Abstract

UVB radiation suppresses photosynthesis and protein biosynthesis in plants, which in turn decreases growth and productivity. Here, an ultraviolet-B (UVB)-tolerant rice mutant, utr319 (UV Tolerant Rice 319), was isolated from a mutagenized population derived from 2500 M1 seeds (of the UVB-resistant cultivar ‘Sasanishiki’) that were exposed to carbon ions. The utr319 mutant was more tolerant to UVB than the wild type. Neither the levels of UVB-induced cyclobutane pyrimidine dimers (CPDs) or (6-4) pyrimidine-pyrimidone photodimers [(6-4) photoproducts], nor the repair of CPDs or (6-4) photoproducts, was altered in the utr319 mutant. Thus, the utr319 mutant may be impaired in the production of a previously unidentified factor that confers UVB tolerance. To identify the mutated region in the utr319 mutant, microarray-based comparative genomic hybridization analysis was performed. Two adjacent genes on chromosome 7, Os07g0264900 and Os07g0265100, were predicted to represent the mutant allele. Sequence analysis of the chromosome region in utr319 revealed a deletion of 45 419 bp. RNAi analysis indicated that Os07g0265100 is most likely the mutated gene. Database analysis indicated that the Os07g0265100 gene, UTR319, encodes a putative protein with unknown characteristics or function. In addition, the homologs of UTR319 are conserved only among land plants. Therefore, utr319 is a novel UVB-tolerant rice mutant and UTR319 may be crucial for the determination of UVB sensitivity in rice, although the function of UTR319 has not yet been determined.

Heavy-ion beam mutagenesis identified an essential gene for chloroplast development under cold stress conditions during both early growth and tillering stages in rice

“…In previous studies, Ishikawa et al 37) reported that three lowcadmium-accumulating rice mutant lines induced by carbon ions possessed a 1-bp deletion, <227-kb deletion, and 433-bp insertion accompanied with an insertion of mPingA1, a kind of transposable element in rice, respectively. Takano et al 38) reported that they found a 45,419-bp-deletion in the ultraviolet-B-tolerant rice mutant induced by carbon ions. Although there is not sufficient information to draw conclusions at this point, these data, with ours included, suggest that carbon ions are possibly a mutagen that can induce various types of mutations such as small deletion, large deletion, and translocation in the rice genome, as in the case of Arabidopsis.…”

An ion beam–induced Arabidopsis mutant with marked chromosomal rearrangement

“…Therefore, it is predicted that ion beams induce marked mutations, including deletions, insertions, inversions, duplications and/or translocations. Supporting this idea, several mutant plants carrying an inversion [ 12 , 17 , 29 ] or deletion [ 32 , 33 ] within a given chromosome have been reported. Moreover, cytological analysis using tobacco cultured cells has shown that abnormal chromosomes such as minichromosomes or bridge structures are induced by ion beams [ 34 , 35 ], suggesting that ion beams induced aberrations involving plural chromosomes.…”

Recent advances of microbial breeding via heavy-ion mutagenesis at IMP

“…For example, through comparative genomic hybridization (array CGH) analysis between wild‐type and utr319 rice mutant induced by carbon ions, Takano et al . () found that Os07g026510 gene in rice contributed to ultraviolet‐B (UVB: 280–320 nm) tolerance. Using DNA microarray techniques, Hwang et al .…”

“…Presently, a series of studies have been performed to investigate the mechanisms for desired phenotype plant mutants induced by heave-ion irradiation. For example, through comparative genomic hybridization (array CGH) analysis between wild-type and utr319 rice mutant induced by carbon ions, Takano et al (2013) found that Os07g026510 gene in rice contributed to ultraviolet-B (UVB: 280-320 nm) tolerance. Using DNA microarray techniques, Hwang et al (2014) found that 220 MeV l À1 carbon ions (LET = 107 keV l À1 ) can induce up-regulated gene expression related to sugar and starch accumulation in rice.…”