Abstract
Sphingoid base 1-phosphates are resolved into ethanolamine-phosphate and C16-fatty aldehyde catalyzed by sphingosine phosphate lyase (SPL). In this study, to clarify the physiological role of SPL in Arabidopsis, we performed gene expression analysis of an Arabidopsis SPL gene, AtSPL1, and functional analysis of spl mutants. AtSPL1 transcripts were slightly decreased by low humidity stress. To assess the functional consequence of the loss of function of AtSPL1, we characterized two independent Arabidopsis mutants (atspl1-1 and atspl1-2) with T-DNA insertions in the AtSPL1 gene. The phenotype of atspl1-1 and atspl1-2 was indistinguishable from wild-type plants under normal growth conditions. Next, we compared the rate of water loss in excised leaves from wild-type and mutant plants. The mutant plants showed slower water loss than wild-type plants. Futhermore, we found that stomatal closing in the two lines was more sensitive to ABA than in the wild type.
