<Emphasis Type="Italic">AVAG2</Emphasis> is a putative D-class gene from an ornamental asparagus

Members of the AGAMOUS (AG) family of MADS-box genes play important roles in regulating the development of reproductive organs in flowering plants. To elucidate the molecular mechanisms of floral development in Asparagus virgatus, we isolated and characterized an Asparagus AG-homologue, AVAG2. AVAG2 contains an open reading frame that encodes a deduced protein with 234 amino acid residues. Phylogenetic analysis indicated that AVAG2 belongs to the D-lineage of the AG gene family. AVAG2 mRNA was detected in the flower, but not in vegetative organs. Moreover, in in situ hybridization experiments, AVAG2 signals were observed in the stamens and carpels during early flower development, and appeared in the ovule only at later developmental stages. This suggests that the AVAG2 gene is involved in ovule formation. Thus, our expression data support the phylogenetic analysis indicating that AVAG2 belongs to the D-class gene family.     

Alteration of floral organ identity in rice through ectopic expression of<Emphasis Type="Italic"> OsMADS16</Emphasis>

We used a transgenic approach and yeast two-hybrid experiments to study the role of the rice ( Oryza sativa L.) B-function MADS-box gene, OsMADS16. Transgenic rice plants were generated that ectopically expressed OsMADS16 under the control of the maize ( Zea mays L.) ubiquitin1 promoter. Microscopic observations revealed that the innermost-whorl carpels had been replaced by stamen-like organs, which resembled the flowers of the previously described Arabidopsis thaliana (L.) Heynh. mutation superman as well as those ectopically expressing the AP3 gene. These results indicate that expression of OsMADS16 in the innermost whorl induces stamen development. Occasionally, carpels had completely disappeared. In addition, ectopic expression of OsMADS16 enhanced expression of OsMADS4, another B-function gene, causing superman phenotypes. In the yeast two-hybrid system, OsMADS16 did not form a homodimer but, rather, the protein interacted with OsMADS4. OsMADS16 also interacted with OsMADS6 and OSMADS8, both of which are homologous to SEPALLATA proteins required for the proper function of class-B and class-C genes in Arabidopsis. Based on the gene expression pattern and our yeast two-hybrid data, we discuss a quartet model of MADS-domain protein interactions in the lodicule and stamen whorls of rice florets.     

SEEDSTICK Controls Arabidopsis Fruit Size by Regulating Cytokinin Levels and FRUITFULL

1. Download : Download high-res image (152KB)
2. Download : Download full-size image

     

Molecular cloning and characterization of NFBP6, a putative floral homeotic gene, from tobacco

 NFBP6 cloned from tobacco is most closely related to petunia FBP6, a putative C-function gene. Also, NFBP6 is expressed specifically in stamens and carpels. Thus, NFBP6 provides a useful tool for molecular characterization of flower development.