The effects of increased expression of an Arabidopsis HD-ZIP gene on leaf morphogenesis and anther dehiscence

Of the homeodomain protein superfamily homeodomain-leucine zipper (HD-ZIP) proteins form a plant-specific subfamily. A number of HD-ZIP transcription factors have been reported to play important roles in various aspects of plant growth and development, however, functions of most members remain unknown. Here, we report the characterization of an Arabidopsis semidominant mutant, upcurved leaf1 (ucl1). Besides having upcurved leaves, the homozygous mutant plants are male sterile due to anther non-dehiscence. Molecular and genetic analysis indicated that the phenotypes of ucl1 were resulted from increased expression of At2g32370, which encodes a member of class IV HD-ZIP protein, HDG3. We isolated the full-length cDNA of HDG3 and found a splicing site different from the annotated information. RT-PCR analysis indicated that HDG3 is specifically expressed in flowers and the promoter-GUS analysis revealed that it is only expressed in anthers. In homozygous ucl1 anthers, the expression levels of three positive regulators of anther dehiscence, MYB26, NST1 and NST2 were down-regulated. Taken together, our data demonstrate that HDG3 plays a negative role in role in regulation of anther dehiscence.