Abstract
We isolated a recessive mutant slh1 (sensitive to low humidity 1) from Arabidopsis Ds transposant lines. When young plants were transferred to soil, slh1 gradually died with necrotic lesions. When slh1 was directly sowed to soil, plants showed dwarf phenotype with tiny, wilty, and dark green leaves. slh1 could grow and bear fruits at high humidity condition. The serious weakness for drought of slh1 could not be suppressed by exogenous ABA. Microscopy analysis revealed that slh1 dwarfism was caused by decreased cell size. cDNA microarray hybridization monitored global transcriptional changes of defense related genes. Northern blot analysis showed that constitutive expression of marker genes for hypersensitive response. Dead cells and accumulation of callose and autofluorescence in slh1 rosette leaves were detected by trypanblue and anylineblue staining, respectively. These results indicate that slh1 is a mutant which develop HR-like lesions and activate defense responses in the absence of pathogens.
