Regulation of Plant Growth & Development

Show abstractHide abstract

Control of plant growth depends on the comprehensive understanding of phytohormone function and establishment of technologies to regulate the function. Here I report two basic studies and one application-oriented study. Pharbitis 'uzukobito' is a recessive mutant showing extremely dwarf phenotype. Exogenous application of brassinosteroid biosynthetic intermediates and analysis of endogenous brassinosteroids suggested a defect of PnDET2, a homologous enzyme of arabidopsis DET2. The cloning and function assay demonstrated the mutation and the functional loss of the enzyme of uzukobito. AGPs constitue a family of glycoproteins. The specific binder of AGPs (Yariv) showed the involvement of AGPs in GA function in barley aleurone cells. Microarray analysis showed that Yariv is an overall repressor of GA-responsive gene expression, and the reagent also activated defense-related signaling. Well-established defense system inducers such as jasmonic acid and chitin elicitor also inhibited GA-inducible events in aleurone cells, indicating that GA signaling is under the regulation of defense-related signaling. Immunomodulation is a mean to modulate organism function by antibody production to capture either endogenous or exogenous antigen. I applied this method to plants. Production of single-chain antibodies both against bioactive GAs and against their biosynthetic precursors gave clear GA-deficient phenotypes, by repressing GA action and GA biosynthesis, respectively.

View full abstract

Download PDF (1520K)

Extensive studies using the model plant organism Arabidopsis suggested that many developmental processes in plants occur via gene regulation achieved through epigenetic mechanisms such as histone modification and chromatin remodeling. The transition to flowering, prerequisite for reproductive success, has been intensively studied and provided a window to understand epigenetic mechanisms in plants. The potent flowering repressor, FLOWERING LOCUS C (FLC), is epigenetically silenced by vernalization, a long-term cold exposure, conferring upon plants the competence to flower. Conversely, a strong activator of flowering, FT, is epigenetically suppressed during the vegetative growth phase, but is expressed in tissue-specific pattern upon exposure to inductive photoperiod. Here we describe epigenetic changes associated with repressing/activating FLC and FT expression. More generally, we consider recent genome-wide studies of histone modification, DNA methylation and the role of TERMINAL FLOWER 2 (TFL2) / LIKE-HETEROCHROMATIN PROTEIN 1 (LHP1) ; such studies serve to enhance global understanding of epigenetic mechanisms in plants, and illustrate some differences among epigenetic mechanisms used by plants and animals.

View full abstract

Register with J-STAGE for free!