For improvement of plants in disease resistance, it is most important to elucidate the mechanism to perceive and respond to the signal molecules of invaders. A model system with pea and its pathogen, Mycosphaerella pinodes, showed that the fungal elicitor induced defense responses in all plant species tested but that the suppressor of the fungus blocked or delayed the expression of defense responses and induced accessibility only in the host plant. In the world, many researchers believe that the pathogens` signals are recognized only on the receptors in the plasma membranes. Though we found that the ATPase and polyphosphoinositide metabolism in isolated plasma membranes responded to these fungal signals, we failed to detect specific actions of the suppressor in vitro on these plasma membrane functions. Recently, we found that ATPase (NTPases) and superoxide generating system in isolated cell wall were regulated by these fungal signals even in vitro, especially, by the suppressor in a strictly species-specific manner and also that the cell wall alone prepared an original defense system. The effects of both fungal signals on the isolated cell wall functions in vitro coincide perfectly with those on defense responses in vivo. In this treatise, we discuss the key role of the cell wall, which is plant-specific and the most exterior organelle, in determining host-parasite specificity and molecular target for improvement of plants.

Genome and chromosome analyses in plants using fluorescence in situ hybridization (FISH) and immuno-staining (IMS) methods are reviewed by presenting the recent results obtained by the Chromosome Link, a group of chromosome and genome researchers. FISH is now effective to detect unique nucleotide sequences with 153 bp on the extended DNA fibers. Genomic in situ hybridization (GISH) also allows painting plant chromosomes of different genomes. GISH is quite effective to detect the genomic differentiation in the individual chromosomes within a nucleus. Three dimensional (3D) analyses are now available by confocal microscopy and a deconvolution system. These techniques are invaluable to visualize both the structural and functional dynamics within a nucleus. 3D-FISH revealed the spatial differentiation of different genomees within a nucleus. 3D-FISH also proved structural partition of centromeric and telomeric domains within a barely nucleus. The dynamic acetylation of histone H4 at the specific regions of a genome during a cell cycle is also analyzed using 3D-IMS. It is anticipated that these methods will provide us powerful tools to understand the structural and functional significance of plant chromosomes and genomes.

White and blue/white varieties of Torenia hybrida cv. Summerwave (SWB) were successfully obtained from the blue variety of by cosuppressing gene expression of two of the enzymes involved in anthocyanin biosynthesis; chalcone synthase (CHS) and dihydroflavonol 4-reductase (DFR). Such molecular brceding is the only precise and efficient way to widen the flower color variation of SWB due to its male and female sterility. Flower color and the degree of suppression varies depending on the transgenic lines. The dorsal and ventral petal lobes and corolla tube consistently lose anthocyanins prior to lateral petal lobes. A pink variety was also obtained by cosuppressing the flavonoid 3`5`-hydroxylase (F3`5`H) gene. Yellow torenia was obtained from T-33, an in-house cultivar that contained both carotenoids and anthocyanins, by blockage of anthocyanin biosynthesis with cosuppressing CHS or DFR genes.

The plant pigment proteins phytochromes are a molecular light sensor or switch for photomorphogenesis involving a variety of growth and developmental responses of plants to red and far-red wavelength light. Underscoring the photomorphogenesis mediated by phytochromes is the light signal transduction at molecular and cellular levels. For example, a number of genes activated by the phytochrome-mediated signal transduction cascade have been identified and characterized, especially in Arabidopsis thaliana. The light sensor/switch function of phytochromes are based on photochromism of the covalently linked tetrapyrrole chromophore between the two photoreversible forms, Pr and Pfr. The photochromism of phytochromes involves photoisomerization of the tetrapyrrole chromophore. The "photosensor" Pr-form ("switch off" conformation) of phytochromes strongly absorbs 660 nm red light, whereas the "switch on" Pfr-conformation preferentially absorbs 730 nm far-red light. The latter is generally considered to be responsible for eliciting transduction cascades of the red light signal for various responses of plants to red light including positive or negative expression of light-responsive genes in plant nuclei and chloroplasts. In this paper, we discuss the structure-function of phytochromes in plant growth and development, with a few examples of biotechnological implications.