Roles of the ASYMMETRIC LEAVES2 gene in floral organ development in Arabidopsis thaliana

Abstract

The ASYMMETRIC LEAVES2 (AS2) gene in Arabidopsis thaliana, a member of the AS2/LOB gene family, is involved in the development of a symmetrical expanded lamina, with the rachis as the axis. On flowering, transcripts of AS2 were detected in inflorescence meristems, floral meristems, and primordia of all floral organs. Levels of accumulation of AS2 transcripts were then decreased in the late stage of the floral organ primordia. β-glucuronidase (GUS) activities were examined in transgenic plants that had been transformed with the GUS gene controlled by the AS2 promoter and were detected in early stages of flower development. We quantified the length of floral organs at each developmental stage. Our results showed that the ratios of lengths of stamen to sepal and carpel to sepal in the as2-1 and as1-1 mutants were larger than those seen in wild-type plants in stages 12 to 14. Furthermore, the changes in the ratios of the lengths of floral organs in as2-1 and as1-1 mutants were suppressed by the mutations of class 1 KNOX genes. These results indicate that AS2 and AS1 genes would control the balance of the floral organ lengths via repressing class 1 KNOX genes in reproductive stages.