The homeobox gene BREVIPEDICELLUS is a key regulator of inflorescence architecture in Arabidopsis

Abstract

Flowering plants display a remarkable range of inflorescence architecture, and pedicel characteristics are one of the key contributors to this diversity. However, very little is known about the genes or the pathways that regulate pedicel development. The brevipedicellus (bp) mutant of Arabidopsis thaliana displays a unique phenotype with defects in pedicel development causing downward-pointing flowers and a compact inflorescence architecture. Cloning and molecular analysis of two independent mutant alleles revealed that BP encodes the homeodomain protein KNAT1, a member of the KNOX family. bp-1 is a null allele with deletion of the entire locus, whereas bp-2 has a point mutation that is predicted to result in a truncated protein. In both bp alleles, the pedicels and internodes were compact because of fewer cell divisions; in addition, defects in epidermal and cortical cell differentiation and elongation were found in the affected regions. The downward-pointing pedicels were produced by an asymmetric effect of the bp mutation on the abaxial vs. adaxial sides. Cell differentiation, elongation, and growth were affected more severely on the abaxial than adaxial side, causing the change in the pedicel growth angle. In addition, bp plants displayed defects in cell differentiation and radial growth of the style. Our results show that BP plays a key regulatory role in defining important aspects of the growth and cell differentiation of the inflorescence stem, pedicel, and style in Arabidopsis.

CUC1 gene activates the expression of SAM‐related genes to induce adventitious shoot formation

“…bp-101 was isolated in our lab, originally from seeds of Ler ecotype that had been mutagenized by ethyl methanesulphonate (EMS). bp-101 has a shoot phenotype with defects in pedicel development as that have been previously reported by Douglas et al (2002) and Venglat et al (2002). Sequence analysis revealed that bp-101 carries a single base change in the homeodomain of the BP gene that alters Trp 326 into an opal stop codon.…”

KNOX genes: versatile regulators of plant development and diversity

“…Defective internode patterning is also observed in rice plants in which the related gene Oryza sativa homeobox15 (OSH15) is mutated (Sato et al, 1999). However, the flower stalks, or pedicels, are specifically shortened and curved downwards in bp mutants, owing to defects in cell division, cell elongation and cell differentiation (Douglas et al, 2002;Venglat et al, 2002), and it remains unclear which aspects of BP function are shared between this tissue and the SAM. KNAT6 and KNAT2 are part of a segmental chromosomal duplication in Arabidopsis, and single mutations in these genes do not affect shoot development (BellesBoix et al, 2006;Byrne et al, 2002).…”

“…3C,D) (Byrne et al, 2003;Douglas et al, 2002;Smith and Hake, 2003;Venglat et al, 2002). Plant architecture consists of repeating modules produced at the SAM called phytomers, each containing an internode, leaf and axillary meristem (Fig.…”

Interaction ofKNAT6andKNAT2withBREVIPEDICELLUSandPENNYWISEinArabidopsisInflorescences

“…bp mutants are characterized by reduced stature, partial loss of apical dominance, and downward-oriented siliques (Douglas et al, 2002;Venglat et al, 2002;Smith and Hake, 2003). Figure 1 shows the phenotypes of the main inflorescences of the bp, knat2 bp, knat6 bp, and knat2 knat6 bp mutants.…”

“…BP plays a primary role in inflorescence growth, as indicated by bp mutants that exhibit reduced internode and pedicel lengths, bends at nodes, and downward-oriented siliques (Douglas et al, 2002;Venglat et al, 2002;Smith and Hake, 2003). PNY influences inflorescence architecture and fruit development (Byrne et al, 2003;Smith and Hake, 2003;Bhatt et al, 2004).…”