ヒストン修飾が変化することで，ゲノムワイドに遺伝子の発現が制御される．このヒストン修飾変化は，クロマチン免疫沈降（ChIP）や抗修飾ヒストンモノクローナル抗体による免疫染色によって解析されてきた．ヒストン修飾の変化をリアルタイムで解析できれば，経時的なダイナミクスを捉えることができる．我々は，ヒストン修飾を認識する蛍光プローブを用いたライブセルイメージングによって，ヒストン修飾を生きた植物細胞で可視化する技術を確立した．特定のヒストンアセチル化を認識する抗体をもとに作成した蛍光プローブmintbody（modification specific intracellular antibody） を植物培養細胞に遺伝子導入した．その結果，細胞内の蛍光プローブはヒストン修飾を認識し，ヒストン修飾のレベルに応じて核の内外を移行することが明らかとなった．このヒストン修飾ライブイメージング技術によって，植物細胞内のヒストン修飾をリアルタイムで捉えることが可能になった．
Visualization of cytoskeletal organizations is a fundamental research method for understanding plant cell activities. Conventionally, immunostaining methods have been used to visualize cytoskeletons, but some technical difficulties make it hard to obtain a large number of reliable microscopic images. The introduction of fluorescent protein tagging technology and the development of high-throughput method for microscopic image acquisition have made it easier and quicker to obtain many reliable microscopic digital images of cytoskeletons. Based on these technical improvements, a method for quantitative evaluation of cytoskeletal organizations by image analysis has been developed. This method has become an indispensable research approach in state-of-the-art plant cell biology. In this minireview, I outline a practical method to measure image features to quantitatively evaluate the orientation, parallelness, bundling, and density of cytoskeletons using the ImageJ image analysis software.
Florigen is a mobile signal that initiates flowering, which is generated in leaves in response to various environmental stimuli and is transported to the shoot apical meristem (SAM) in plants. The molecular nature of florigen was found to be proteins encoded by the gene FLOWERING LOCUS T (FT) and its orthologs. Recent progress in the molecular biology of florigen revealed its receptors and a transcriptional complex composed of florigen, receptor and transcription factors. In vivo imaging of florigen distribution in the shoot apex and inside a cell contributed to elucidate the essential mechanisms for florigen function. In rice shoot apex, distribution of florigen is clearly visualized by expression of FT protein fused with green fluorescent protein (GFP), and the spatial patterns of downstream gene expression are also visualized by various techniques. At the cellular level, the distribution of florigen and its receptor complex is observed through bimolecular fluorescent complementation (BiFC), which revealed dynamic changes of subcellular localization for florigen and related proteins during the formation of florigen-receptor complex. Here the technique for dissecting SAM is presented to show how SAM samples are prepared for imaging florigen, and recent advances in the regulation of flowering in relation to the contributions from the application of imaging techniques are summarized.
Floral development is an important discipline within plant morphology, which in turn is the oldest botanical discipline. Recent achievements in molecular phylogeny, physiology and ecology have recalled the importance of floral development. To evaluate its contemporary relevance, we organized the JPR (Journal of Plant Research) symposium about the floral development. This symposium was co-organized by the Japanese Society of Plant Morphology and Fundación Flores (Chile).
Following the historical finding on the important contribution of endoreduplication on cell enlargement in the epidermis of leaves and hypocotyls, sometimes people misunderstand that cell size is always proportional to ploidy level. However, it was found that the impact of tetraploidization on cell size differs among cell types. More importantly, while endoreduplication occurs also in parenchymatous cells as well as epidermis in leaves, cell size of parenchymatous cells is very uniform. Our detailed analyses showed that the impact of endoreduplication on cell size is tissue-identity-dependent. Past reports on the relationship among changes in endoreduplication, cell size and organ size should be re-examined considering the above fact.
Chloroplasts (plastids) are able to synthesize energy-containing macromolecules for a great deal of living organisms. Consistent with their endosymbiotic origin, plastids maintain themselves by binary division. Plastid division is carried out by a ring complex called the plastid-dividing (PD) machinery; the PD machinery has inner and outer ring structures across the plastid membranes. Although many studies have been done to reveal the mechanisms of plastid division, much about the components and molecular mechanisms of the PD machinery remain to be discovered. My work demonstrated that: (1) the contractile force of the PD ring is generated via filament-sliding movement by dynamin proteins; (2) the PD ring is composed of polyglucan nanofilaments, synthesized by the glucosyltransferase PDR1; and (3) examination of the FtsZ ring reconstituted in a heterologous system revealed the assembly and contractile dynamics of the FtsZ ring. In addition, we have recently established isolation of the mitochondriondividing (MD) machinery and revealed that the ultrastructure and the dynamics of the isolated MD machinery were similar to those of the isolated PD machinery. Therefore, plastids and mitochondria divide by the action of supramolecular complexes “the PD and MD machineries” including dual contractible rings, the PD/MD ring and the FtsZ ring. These findings will lead to an understanding of how plastids and mitochondria were established during evolution.