Sympodial Plant Research Articles

Tomato APETALA2 family member SlTOE1 regulates inflorescence branching by repressing SISTER OF TM3.

Inflorescence architecture directly impacts yield potential in most crops. As a model of sympodial plants, tomato (Solanum lycopersicum) inflorescence exhibits highly structural plasticity. However, the genetic regulatory network of inflorescence architecture in tomato remains unclear. Here, we investigated a modulator of inflorescence branching in tomato, TARGET OF EAT1 (SlTOE1), an APETALA2 (AP2) family member found to be predominantly expressed in the floral meristem (FM) of tomato. sltoe1 knockout mutants displayed highly branched inflorescences and defective floral organs. Transcriptome analysis revealed that SISTER OF TM3 (STM3) and certain floral development-related genes were upregulated in the flower meristem of sltoe1. SlTOE1 could directly bind the promoters of STM3 and Tomato MADS-box gene 3 (TM3) to repress their transcription. Simultaneous mutation of STM3 and TM3 partially restored the inflorescence branching of the sltoe1cr mutants, suggesting that SlTOE1 regulates inflorescence development, at least in part through an SlTOE1STM3/TM3 module. Genetic analysis showed that SlTOE1 and ENHANCER OF JOINTLESS 2 (EJ2) additively regulate tomato inflorescence branching; their double mutants showed more extensive inflorescence branching. Our findings uncover a pathway controlling tomato inflorescence branching and offer deeper insight into the functions of AP2 subfamily members.

Deregulation of MADS-box transcription factor genes in a mutant defective in the WUSCHEL-LIKE HOMEOBOX gene EVERGREEN of Petunia hybrida

ABSTRACTAngiosperm inflorescences develop in two fundamentally different ways. In monopodial plants, for example in Arabidopsis thaliana, the flowers are initiated as lateral appendages of a central indeterminate inflorescence meristem. In sympodial plants, flowers arise by terminal differentiation of the inflorescence meristem, while further inflorescence development proceeds from new sympodial meristems that are generated at the flank of the terminal flower. We have used the sympodial model species Petunia hybrida to investigate inflorescence development. Here, we describe a mutant, bonsai (bns), which is defective in flower formation, inflorescence branching, and control of meristem size. Detailed microscopic analysis revealed that bns meristems retain vegetative charateristics including spiral phyllotaxis. Consistent with a block in flower formation, bns mutants exhibit a deregulated expression of various MADS-box genes. Molecular analysis revealed that the bns mutant carries a transposon insertion in the previously described EVERGREEN (EVG) gene, which belongs to the WUSCHEL-LIKE HOMEOBOX (WOX) transcription factor gene family. EVG falls in the WOX9 subfamily, which has diverse developmental functions in angiosperms. The comparison of WOX9 orthologues in five model species for flowering shows that these genes play functionally divergent roles in monopodial and sympodial plants, indicating that the WOX9 regulatory node may have played an important role in the evolution of shoot architecture.

Biomorphological adaptations of helophytes

Nine species of helophytes are described using a systematic approach: Alisma plantago-aquatica, Butomus umbellatus, Sagittaria sagittifolia, Sparganium emersum, Glyceria maxima, Phragmites australis, Scirpus lacustris, Typha latifolia, and T. angustifolia. The species are divided into four groups according to their characteristics: monopodial rosette plants with a short rhizome, sympodial semirosellate plants with a short rhizome, sympodial semirosellate tuberous plants, and sympodial plants with a long rhizome. It is determined that seed individuals and vegetative descendants of polycarpic plants tend to become short-lived. This trend is implemented in different ways.

Mechanics and Growth Form of the MossHylocomium splendens

The mossHylocomium splendenshas two different growth forms. Sympodial growth occurs where the apical meristem ceases activity annually and growth is continued by a lateral bud. Sympodial plants are vertical and self-supporting. Monopodial growth occurs when the apex continues growth. Monopodial plants are prostrate. The aims of the study were to examine stem mechanics of the different growth forms and to compare mechanical properties along stems. Stems of annual segments were subjected to three point bending tests. In sympodial plants the stiffness of the stem material increased significantly with segment age. Flexural rigidity increased significantly with age in segments from 1 to 4 years old, and then declined. Segment diameter decreased significantly with age in sympodial plants. Monopodial plants showed no significant effects of segment age on the diameter, material stiffness or flexural rigidity of stems. Sympodial segments were significantly wider, stronger, more rigid and composed of stiffer material with a higher stress at yield than monopodial segments, but did not have a larger proportion of strengthening material. Sympodial stems had significantly more cellulose than monopodial stems. The mossHylocomium splendensshows a range of mechanical adaptations, as a self-supporting or a prostrate plant, which suit it to life in very different environments.