JOINTLESS suppresses sympodial identity in inflorescence meristems of tomato

Abstract

Unlike monopodial plants, in which flowering terminates growth of a shoot, plants exhibiting sympodial shoot architecture maintain the potential for indeterminate growth even after converting to floral development. This vegetative indeterminacy is conferred by a special type of axillary meristem, the sympodial meristem, which exhibits precocious but determinate growth. The reiterative formation of sympodial meristems as the plant grows results in a shoot composed of a series of modules, each consisting of a limited number of vegetative nodes and terminated by a flower or inflorescence. To determine how sympodial meristems differ from other shoot meristems, we examined interactions between mutations that affect various shoot meristem types in tomato (Lycopersicon esculentum Mill.). Analysis of double mutant combinations of jointless, lateral suppressor, self-pruning, blind, and anantha showed that sympodial meristems share regulatory features with inflorescence meristems. Genetic studies on the jointless mutation implicated this gene in suppressing sympodial meristem fate in the inflorescence. As this mutation has a second phenotype, the elimination of the pedicel abscission zone, we examined the expression pattern of JOINTLESS to test whether pedicel development is involved in directing shoot architecture. We found that this MADS box gene is expressed in a variety of shoot meristems, including inflorescence, floral, sympodial, and axillary meristems, as well as in early staged floral organs, in sporogenous tissues of anthers, and in ovules. Lack of expression in developing pedicels indicates abscission zone development does not rely on JOINTLESS transcription in the differentiating cells. We conclude that the primary role of JOINTLESS is to suppress sympodial meristem identity in inflorescence meristems.

Diversity among Modern Tomato Genotypes at Different Levels in Fresh-Market Breeding

“…With fresh-market tomato, some of the important traits that have been of main focus for producer are yield or size, disease and insect resistance, heat and other abiotic stress tolerance, uniform/synchronous ripening, and harvesting with focus in mechanization; for marketing are longer shelf life, minimum handling, and shipping damage; and for consumer are flavor and taste, appearance/color, and forms of use like salad and cooking [20][21][22]. The jointless (j2) allele [23] was introgressed from S. cheesmanii. Compact fruit set by determinate growth, sp for self-pruning, was discovered from a natural mutation in the early 20th century.…”

Short Vegetative Phase-Like MADS-Box Genes Inhibit Floral Meristem Identity in Barley

“…SVP and AGL24) is known to cause floral reversion in Arabidopsis. The ability of SVP-like genes to trigger floral reversion is not an artifact of ectopic expression; in tomato (Lycopersicon esculentum), indeterminant sympodial growth is achieved through successive floral reversions, where an inflorescence develops below the flower on an otherwise determinant floral branch (Szymkowiak and Irish, 2006). A SVP-like gene, JOINTLESS, is required to generate an inflorescence meristem (the sympodial meristem) below the flower and is essential for sympodial growth (Szymkowiak and Irish, 2006).…”

Genetic analysis of reproductive development in tomato

“…2), allowing normal shoot formation and indicating that maintenance of IM identity requires J and MC genes (Rick and Sawant, 1955;Rick and Butler, 1956;Vrebalov et al, 2002;Szymkowiak and Irish, 2006). Also the identity of IM is lost in the sft mutant after one or two flowers are developed (Fig.…”

“…2). Molecular characterization of these genes and their interactions with meristem identity genes support this functional role (Mao et al, 2000;Schmitz et al, 2002;Szymkowiak and Irish, 2006).…”