Accumulation of sense–antisense transcripts of the rice catalase gene CatB under dark conditions requires signals from shoots

The amount of mRNA of the Oryza sativa L., cv. Nipponbare (rice) catalase gene, CatB, was decreased in the roots of intact seedlings kept in continuous darkness (DD). In contrast, sense and antisense unspliced CatB transcripts accumulated in the same tissue. Both strands cover the entire CatB-coding region, and form double-stranded RNA (dsRNA). The results of RNA dot-blot hybridization analysis using low molecular weight RNAs suggested that the sense and antisense CatB transcripts were more stable under DD conditions than under a light–dark regimen (LD). After shifting the lighting conditions from DD to LD, both the sense and antisense CatB transcripts were hardly detected, and the amount of CatB mRNA was restored. From these results, the antisense CatB transcripts might play a role in suppressing the normal processing of sense CatB transcript and also CatB protein synthesis by dsRNA formation, under conditions unsuitable for plant growth such as DD. This study indicates that signals transmitted from shoots are associated with the accumulation of sense and antisense CatB transcripts in roots under DD conditions, and that auxin is one of the possible signals.