Spatial and Temporal Expression of Cold-responsive DEAD-box RNA Helicases Reveals their Functional Roles During Embryogenesis in Arabidopsis thaliana

Abstract

DEAD-box RNA helicases compose a large subfamily of RNA helicases found in all eukaryotes and prokaryotes. Functional DEAD-box RNA helicases are considered to be RNA chaperones that modify RNA secondary structure and perhaps three-dimensional structures during different cellular processes involving RNA metabolism. Although a relationship of DEAD-box RNA helicases to abiotic stress adaptation is known, few reports document the involvement of RNA helicases during plant growth and development. In this study, detailed analyses were performed for two cold-responsive DEAD-box RNA helicases, AtRH22 and AtRH52, on the transcript level during different developmental stages of Arabidopsis thaliana. Expression levels of AtRH22 and AtRH52 were up-regulated markedly in response to cold stress and were enriched in shoot apical meristems, floral buds, and siliques. The expression of AtRH22 and AtRH52 was spatiotemporally regulated during vegetative growth, floral transition and embryonic development. To investigate, the functional role of AtRH22 and AtRH52 in A. thaliana, we functionally characterized independent T-DNA insertion mutant lines for both genes. Genotypic analysis of self-fertilized heterozygous lines revealed only heterozygous (WT/T-DNA) and homozygous wild-type progeny for AtRH22 and AtRH52. Self-fertilized heterozygous mutants of AtRH22 and AtRH52 show normal vegetative phenotype, but produced normal-sized and abortive seeds. Collectively, these results demonstrate that the cold-responsive AtRH22 and AtRH52 genes are spatiotemporally regulated during plant development and are essential during Arabidopsis embryogenesis.