Cell-to-cell communication plays an important role in development, reproduction, and environmental responses by coordinating the cell activity in multicellular organisms. In plant development, cell-to-cell communication is especially crucial because organogenesis is a postembryonic and continuous process. However, it is difficult to reveal the dynamics of intercellular communications due to the limitation of accessibility within several cell layers in plants. Recently, two-photon excitation microscopy with near-infrared femtosecond pulse laser provides a non-invasive tool for deep imaging. In this review, we discuss recent deep imaging containing the preparation of specimens and microscopic techniques. Moreover, optical manipulation technique with near-infrared ultrafast pulse laser enables us to disrupt the cell and the protein at the single-cell level. Combination of in vivo deep imaging and optical manipulation, which allow spatial and temporal control of cell activity, provides a new view of the cell-to-cell communication in plant field.

Live imaging was brought about by recent development of fluorescent proteins and innovation of imaging systems. Dynamic analyses of organelle through live imaging reveal the subcellular dynamic function and the spatiotemporally four-dimensional structure. At the same time, quantitative analyses in addition to qualitative analyses become more important in analyses of the huge imaging data. Thus, we introduce our recent works in live imaging of mitochondria, nuclei, vacuolar membrane, and actin filaments in plant cells with our observation skills. Moreover, quantitative analyses of live imaging data were classified into three categories, number, morphology and distribution, three dimensional shape or dynamics. We review these three quantitative analyses.

Florigen is a systemic signal that promotes flowering. Its molecular nature is a conserved FLOWERING LOCUS T (FT)/ Heading date 3a (Hd3a) protein with small globular structure. FT/Hd3a protein is synthesized in leaves, transported into shoot apical meristem to initiate floral transition. Key question in this process is how florigen exerts this transition in the shoot apical cells. Imaging Hd3a proteins and its partner proteins in living cells revealed dynamic process regulating the formation of transcriptional protein complex in the nucleus. We developed two techniques for quantification of protein-protein interaction by bimolecular fluorescent complementation (BiFC) assay and for detection of tripartite protein complex by combining BiFC and foster resonance energy transfer (FRET), which is measured by fluorescence life-time imaging microscopy (FLIM). These techniques allow us to observe the formation of Hd3a-14-3-3-OsFD1 complex in living cells. Hd3a interacts with 14-3-3 proteins in the cytoplasm, then Hd3a-14-3-3 subcomplex translocates into the nucleus to interact with OsFD1 to yield a protein complex that we call florigen activation complex (FAC). The detailed imaging of another FD homolog, OsFD2, revealed that OsFD2 forms FAC in different way from that of OsFD1. These findings help further understanding of florigen function in living cells.

Plant hormones are small molecules and coordinately regulate plant growth and development throughout the plant life. The action of plant hormones is regulated by the distribution and sensitivity of plant hormones modulated by metabolism, transport and signaling. The distribution of plant hormones in the cell and tissue is determined by the rate of biosynthesis and inactivation and transport. Live cell imaging by means of fluorescently-labeled plant hormones is useful approach to obtain spatio-temporal information of plants hormones in living organism. Especially, fluorescently-labeled auxins that designed to be specific to transport system are powerful tool to understand the regulatory process underlying auxin distribution. Here, we give an overview of fluorescent-labeling for plant hormones.

Phytoplasmas are plant pathogenic bacteria associated with devastating damage to over 700 plant species worldwide. It is agriculturally important to identify factors involved in their pathogenicity and to discover effective measures to control phytoplasma diseases. Despite their economic importance, phytoplasmas remain the most poorly characterized plant pathogens, primarily because efforts at in vitro culture, gene delivery, and mutagenesis have been unsuccessful. However, recent molecular studies have revealed unique biological features of phytoplasmas. This review summarizes the history and recent progress in phytoplasma research, focusing on reductive evolution of the genomes and virulence factors involved in their unique symptoms, such as TENGU and Phyllogen.

Under field conditions, environmental factors, e.g. temperature, light and humidity, are dynamically fluctuating. On the other hand, molecular mechanisms of plants have been investigated under simple laboratory conditions. It is difficult to predict plant responses to fluctuating environment only from knowledge obtained in laboratories. In this review, we focused on gene expression analysis under the fields. Integrative analysis between gene expression data and meteorological data tell us novel features of plant environmental responses.

Environmental stresses often cause serious damages to plants, and many cases of environmental stresses are accompanied by oxidative stress derived from overproduced reactive oxygen species (ROS). In chloroplasts under oxidative stress, stimulated peroxidation of polyunsaturated fatty acids by ROS generates reactive carbonyls that can act as toxic and signaling chemicals, RSLVs (Reactive Short-chain Leaf Volatiles). In this note, mechanism of production of reactive carbonyls and their physiological roles in environmental stress response are discussed.

The radioactive cesium released by a nuclear plant accident was dissolved in rainwater and deposited on the land surface. The nuclide was adsorbed strongly by clay fraction as soon as it contacted with the soil and remained in the soil outer layer. Plants absorb various kinds of substances with water from their root, but the cesium in the clay is hardly absorbed.On the other hand, the nuclide moves more easily in sandy soil, peat soil and organic matter layers that accumulated on the forest floor. When cesium is deposited on organic matter, it can be absorbed by plants. The translocation pattern in plants is similar with that of potassium ; transferring and accumulating in the growing part. In the river water, the radioactivity is detected when the soil sediment is contained. It is important to take means not to move a surface soil from the contaminated sites. In forest environments, cesium moves in the ecosystem. The survey of the nuclide deposition at one and a half years after the accident revealed that the radioactivity in the coniferous leaf or bark is approximately reduced to half and that in the soil outer layer increased by degradation of organic matters followed by downward movement by precipitation. The nuclide adsorbed by the soil is hard to move outside the system without artificial disturbance. However, the outflow of the soil by the muddy water is concerned in a steep slope. The preventive measures with an artificial pond, a ditch or the wall will restrain re-pollution.

We Enzyme Research Team, RIKEN, investigate biopolymer synthesis from plant and marine biomass using enzyme, bacteria and plant as biocatalysts. Here, our recent updates on biosyntheses of polyhydroxyalkanoate (PHA) by bacteria and plants are summarized. Also, a new gene delivery technique using peptide-based gene carriers is briefly introduced. The future perspectives on biopolymer synthesis from plant biomass and using plant as a host producer are described at the end of this short review.