"Determinate" and "indeterminate" inflorescences in plants are controlled by a single recessive gene, for example, SELF-PRUNING (SP) in Solanum lycopersicum, TERMINAL FLOWER1 in Arabidopsis, CENTRORADI-ALIS in Antirrhinum, and CENTRORADIALIS-like gene in tobacco. Pepper (Capsicum annuum L.) is an indeterminate species in which shoots grow indefinitely. In this study, we cloned and characterized the pepper SP-like gene (CaSP). RT-PCR revealed that the CaSP transcript accumulates to higher levels in floral buds than in other organs. Comparison of genomic DNA and cDNA sequences from indeterminate and determinate pepper plants revealed the insertion of a single base in the first exon of CaSP in the determinate pepper plants. CaSP is annotated in linkage group 8 (chromosome 6) of the SNU2 pepper genetic map and showed similar synteny to SP in tomato. Transgenic tobacco plants overexpressing CaSP displayed late-flowering phenotypes similar to the phenotypes caused by overexpression of CaSP orthologs in other plants. Collectively, these results suggest that pepper CaSP is an ortholog of SP in tomato.

Wild peppers (Capsicum spp.) are either annual or perennial in their native habitat and their shoot architecture is dictated by their sympodial growth habit. To study shoot architecture in pepper, sympodial development is described in wild type and in the classical recessive fasciculate (fa) mutation. The basic sympodial unit in wild-type pepper comprises two leaves and a single terminal flower. fasciculate plants are characterized by the formation of floral clusters separated by short internodes and miniature leaves and by early flowering. Developmental analysis of these clusters revealed shorter sympodial units and, often, precocious termination prior to sympodial leaf formation. fa was mapped to pepper chromosome 6, in a region corresponding to the tomato SELF-PRUNING (SP) locus, the homologue of TFL1 of Arabidopsis. Sequence comparison between wild-type and fa plants revealed a duplication of the second exon in the mutants' orthologue of SP, leading to the formation of a premature stop codon. Ectopic expression of FASCICULATE complemented the Arabidopsis tfl1 mutant plants and as expected, stimulated late flowering. In agreement with the major effect of FASCICULATE imposed on sympodial development, the gene transcripts were localized to the centre of sympodial shoots but could not be detected in the primary shoot. The wide range of pleiotropic effects on plant architecture mediated by a single 'flowering' gene, suggests that it is used to co-ordinate many developmental events, and thus may underlie some of the widespread variation in the Solanaceae shoot architecture.