terminal flower: a gene affecting inflorescence development in Arabidopsis thaliana

Abstract

Summary Growth of flowering stems in wild‐type Arabidopsis is indeterminate. Many flowers arise sequentially on the flanks of apical meristems in a phyllotactic spiral. We have isolated eight recessive mutants of a gene, terminal flower, in which inflorescences become determinate. Flower primordia sooner or later ‘invade’ the meristem summit leading to cessation of its further growth. Primary apical meristems usually terminate with several part‐flowers which lack pedicels, and several normal pedicellate flowers may arise first. By contrast apical meristems of secondary branches usually produce only a single pedicellate flower. Plant height is also reduced and more rosette inflorescences develop. These growth patterns occur in six strong mutants raised at 25°C under continuous light. In two weak mutants termination occurs much later with many more flowers arising before eventual termination. Termination is similarly delayed in at least one of the strong mutants grown at lower temperatures. The tfl mutation does not affect the indeterminate growth of flower meristems, at least in‐so‐far as this occurs in agamous mutants. The tfl locus is at the top of linkage group 5, close to RFLP 447. We propose that the TFL gene product supports the activity of an inhibitor of flower primordium initiation. This inhibitor would normally prevent flowers from arising on the inflorescence apex but in tfl mutants it may readily fall below its threshold of activity. The TFL gene may be one of a class responsible for evolutionary changes between indeterminate and determinate growth.

Developmental and age-related processes that influence the longevity and senescence of photosynthetic tissues in arabidopsis.

“…The most active period of flowering and fruit development is accompanied by the sequential senescence of the original leaves of the rosette, as indicated by an initial stage of chlorophyll loss, followed by the complete disintegration of the leaf tissue ( Figure 1C). Developmental arrest of the rnain inflorescence stem, characterized by a cessation of proliferative activity at the apex and a degeneration of the youngest flower buds, occurred at approximately day 40 (Vaughan, 1955;Shannon and Meeks-Wagner, 1991;Alvarez et al, 1992). During this later phase, the stem, cauline leaves, and seed pods became senescent and the seeds of the next generation reached maturity ( Figure 1D).…”

“…The transition to flowering, however, marks the beginning of the end for the adult plant because all aerial meristems are converted over to reproductive development. While the tissues produced by the inflorescence and flower meristems are capable of photosynthesis, inflorescence meristems have a limited proliferative capacity; they cease meristematic activity after the production of afew dozen flowers (Shannon and Meeks-Wagner, 1991;Alvarez et al, 1992). Thus, the combination of limited longevity of somatic tissues and the limited proliferative capacity of the inflorescence meristems ultimately limit the life span of the adult Arabidopsis plant.…”

“…These two senescenceassociated (SAG) gene clones were designated SAG2 and SAGA As shown in Figure 5A, RNA gel blot analysis indicated that mRNA levels for both genes are elevated in senescing leaves and inflorescence stems. DNA gel blot analysis, shown Meeks-Wagner, 1991;Alvarez et al, 1992). The Wl-2 line produces a normal rosette and initiates flower development at the same time as the isogenic Ler wild type.…”

“…Columbia seeds were obtained from Chris Somerville (Michigan State University, East Lansing). M7-2 seeds were provided by D. Smyth (Monash University, Melbourne, Australia) (Alvarez et al, 1992).…”

A common mechanism controls the life cycle and architecture of plants

“…TERMINAL FLOWER 1 (TFL1) is a key gene which affects the developmental phases and architecture of Arabidopsis (Shannon and Ry Meeks-Wagner, 1991;Schultz and Haughn, 1991;Alvarez et al, 1992;Ray et al, 1996). The most notable feature of the tfl1 mutant is that a flower forms at the tip of the inflorescence, unlike the wild-type apex which grows indeterminately (Fig.…”