Abstract
To get more insight into the ABA signaling mechanism, we carried out screens for Arabidopsis mutants with altered ABA response. Using an ABA analog, PBI-51, we isolated several ABA hypersensitive mutants named ahg (ABA hypersensitive germination). ahg11, one of these mutants, showed ABA and salt hypersensitivity at seed germination. The corresponding gene for ahg11 was identified by map-based cloning. The predicted gene product is a PPR (pentatricopeptide repeat) protein belonging to a large protein family. The majority of PPRs in Arabidopsis are predicted to function at either chloroplasts or mitochondria. Recently, some PPRs with RNA-binding ability have been reported. Transient expression of an AHG11-GFP fusion protein showed that AHG11 is targeted to mitochondria. This result suggested that AHG11 might be involved in mitochondrial RNA processing. It is unknown and interesting how mitochondrial RNA processing is implicated in ABA response. A detailed analysis of this mutant is now ongoing.
