Abstract: The KNAT1 gene is a member of the Class I KNOX homeobox gene family and is thought to play an important role in meristem development and leaf morphogenesis. Recent studies have demonstrated that KNAT1/BP regulates the architecture of the inflorescence by affecting pedicle development in Arabidopsis thaliana. Herein, we report the characterization of an Arabidopsis T-DNA insertion mutant that shares considerable phenotypic similarity to the previously identified mutant brevipedicle (bp). Molecular and genetic analyses showed that the mutant is allelic to bp and that the T-DNA is located within the first helix of the KNAT1 homeodomain (HD). Although the mutation causes a typical abnormality of short pedicles, propendent siliques, and semidwarfism, no obvious defects are observed in the vegetative stage. A study on cell morphology showed that asymmetrical division and inhibition of cell elongation contribute to the downward-pointing and shorter pedicle phenotype. Loss of KNAT/BP function results in the abnormal development of abscission zones. Microarray analysis of gene expression profiling suggests that KNAT1/BP may regulate abscission zone development through hormone signaling and hormone metabolism in Arabidopsis.(Author for correspondence.State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing 100101, China. Tel: +86 10 6488 9377; Fax: +86 10 6487 3428; E-mail: yhwang@genetics.ac.cn)

Key words: abscission zone, Arabidopsis thaliana, BP/KNAT1, microarray, pedicle.