Chloroplast Development at Low Temperatures Requires a Homolog of DIM1, a Yeast Gene Encoding the 18S rRNA Dimethylase

Open Access
Publisher Website
Google Scholar
Abstract
Poikilothermic organisms require mechanisms that allow survival at chilling temperatures (2 to 15°C). We have isolated chilling-sensitive mutants of Arabidopsis, a plant that is very chilling resistant, and are characterizing them to understand the genes involved in chilling resistance. The T-DNA–tagged mutant paleface1 (pfc1) grows normally at 22°C but at 5°C exhibits a pattern of chilling-induced chlorosis consistent with a disruption of chloroplast development. Genomic DNA flanking the T-DNA was cloned and used to isolate wild-type genomic and cDNA clones. The PFC1 transcript is present at a low level in wild-type plants and was not detected in pfc1 plants. Wild-type Arabidopsis expressing anti-sense constructs of PFC1 grew normally at 22°C but showed chilling-induced chlorosis, confirming that the gene is essential for low-temperature development of chloroplasts. The deduced amino acid sequence of PFC1 has identity with rRNA methylases found in bacteria and yeast that modify specific adenosines of pre-rRNA transcripts. The pfc1 mutant does not have these modifications in the small subunit rRNA of the plastid.