Takumi Yoshida

Comprehensive analysis of rice DREB2-type genes that encode transcription factors involved in the expression of abiotic stress-responsive genes

DREB2s (dehydration-responsive element-binding protein 2s) are transcription factors that interact with a cis-acting DRE (dehydration-responsive element)/CRT (C-repeat) sequence and activate the expression of downstream genes involved in water- and heat-shock stress responses and tolerance in Arabidopsis thaliana. In this study, we performed a comprehensive analysis of all five DREB2-type genes in rice (OsDREB2s: OsDREB2A, OsDREB2B, OsDREB2C, OsDREB2E and OsABI4) to determine which of them contribute to plant stress responses. We analysed the expression patterns of these genes under abiotic stress conditions, and we examined the subcellular localisation and transcriptional activation activity of their translational products in protoplasts. Only OsDREB2A and OsDREB2B showed abiotic stress-inducible gene expression. In addition, OsDREB2B showed nuclear specific localisation and the highest transactivation activity. OsDREB2B has functional and non-functional forms of its transcript similar to its orthologues in the grass family, and the functional form of its transcript was markedly increased during stress conditions. We analysed the splicing mechanism of OsDREB2B with transgenic rice that express the non-functional transcript and we found that the non-functional form is not a precursor of the functional form; thus, stress-inducible alternative splicing of pre-mRNA is an important mechanism for the regulation of OsDREB2B. Transgenic Arabidopsis plants overexpressing OsDREB2B showed enhanced expression of DREB2A target genes and improved drought and heat-shock stress tolerance. These results suggest that OsDREB2B is a key gene that encodes a stress-inducible DREB2-type transcription factor that functions in stress-responsive gene expression in rice.

Arabidopsis HsfA1 transcription factors function as the main positive regulators in heat shock-responsive gene expression

Arabidopsis DREB2A is a key transcription factor of heat- and drought-responsive gene expression, and DREB2A expression is induced by these stresses. We analyzed the DREB2A promoter and found a heat shock element that functions as a cis-acting element in the heat shock (HS)-responsive expression of DREB2A. Among the 21 Arabidopsis heat shock factors, we chose 4 HsfA1-type proteins as candidate transcriptional activators (HsfA1a, HsfA1b, HsfA1d, and HsfA1e) based on transactivation activity and expression patterns. We generated multiple mutants and found that the HS-responsive expression of DREB2A disappeared in hsfa1a/b/d triple and hsfa1a/b/d/e quadruple mutants. Moreover, HS-responsive gene expression, including that of molecular chaperones and transcription factors, was globally and drastically impaired in the hsfa1a/b/d triple mutant, which exhibited greatly reduced tolerance to HS stress. HsfA1 protein accumulation in the nucleus was negatively regulated by their interactions with HSP90, and other factors potentially strongly activate the HsfA1 proteins under HS stress. The hsfa1a/b/d/e quadruple mutant showed severe growth retardation, and many genes were downregulated in this mutant even under non-stress conditions. Our study indicates that HsfA1a, HsfA1b, and HsfA1d function as main positive regulators in HS-responsive gene expression and four HsfA1-type proteins are important in gene expression for normal plant growth.

Functional analysis of an Arabidopsis heat-shock transcription factor HsfA3 in the transcriptional cascade downstream of the DREB2A stress-regulatory system

A transcription factor DREB2A functions as a key regulator not only in drought stress responses but also in heat stress (HS) responses, and activates expression of many abiotic stress-responsive-genes involved in drought and HS tolerance. HsfA3 is one of the most up-regulated heat-inducible genes in transgenic plants overexpressing DREB2A. In this study, the analyses of HsfA3 expression profile and the transactivation analysis of HsfA3 showed that the expression of HsfA3 was directly regulated by DREB2A under HS. Microarray analysis using transgenic plants overexpressing HsfA3 also showed that overexpression of HsfA3 induces many heat-inducible genes. Furthermore, we showed that thermotolerance of the HsfA3 overexpressors was increased, and that of the hsfA3 T-DNA tagged mutants was decreased. These results indicate that HsfA3 regulates expression of many heat-inducible genes in the transcriptional cascade downstream of the DREB2A stress-regulatory system and functions in acquisition of thermotolerance under the control of the DREB2A cascade.

Iron-Catalyzed Chemo- and Stereoselective Hydromagnesiation of Diarylalkynes and Diynes

Diarylalkynes are chemo- and stereoselectively hydromagnesiated in high yields at room temperature with an iron species generated in situ from FeCl(2)and EtMgBr. Functional groups such as bromide, iodide, amine, phenoxide, and alkene are well tolerated. Under similar conditions, diynes are chemo-, regio-, and stereoselectively hydromagnesiated. The resulting alkenylmagnesium compounds are a platform for further functionalization as a one-pot reaction.

Twinkle: Interacting with physical surfaces using handheld projector

We propose a novel interface called Twinkle for interacting with an arbitrary physical surface using a handheld projector and a camera. When a user flashes a projection light on an object, the projected images react as if the user touched the object with the light. The handheld device recognizes the features of the physical environment and displays images and sounds that are generated in real-time according to the users motion and collisions of projected images with objects. We realize this system by using several image-processing techniques and a collision detection algorithm. We also use an acceleration sensor to compensate for the image processing. In this paper, we explain the principle of interacting with a physical surface. Then, we describe the implementation of the prototype system and some application examples.

RePro3D: full-parallax 3D display with haptic feedback using retro-reflective projection technology

We propose a novel full-parallax three-dimensional (3D) display system-RePro3D-that is suitable for interactive 3D applications with haptic feedback.Our approach is based on the retro-reflective projection technology in which several images projected from a projector array are displayed on a retro-reflective screen. When viewers view the screen through a half mirror, they see, without the aid of glasses, a 3D image superimposed in real space. RePro3D has a sensor function that recognizes user input; therefore, it can support some interactive features such as manipulation of 3D objects. In addition, a wearable haptic device, which is a part of our system, provides the user with a sensation of having touched the 3D image. In this paper, we describe the optical system of the high-density projector array used in RePro3D. Then, we describe the development of a prototype of RePro3D. The prototype is used to demonstrate that our system displays full-parallax images superimposed in real space from 42 different viewpoints. The proposed system enables a user to physically interact with the 3D image with haptic feedback.

RePro3D: full-parallax 3D display using retro-reflective projection technology

Motion parallax is important to recognize the depth of a 3D image. In recent years, many 3D display methods that enable parallax images to be seen with the naked eye have been developed. In addition, there has been an increase in research to design interfaces that enable humans to intuitively interact with and operate 3D objects using their hands. However, realizing 3D object interaction as if the user is actually touching the object in the real world is quite difficult. One of the reasons for this is that the screen shape in conventional methods is restricted to a flat panel. In addition, it is difficult to achieve a balance between displaying the 3D image and sensing the user input. Therefore, we propose a novel full-parallax 3D display system that is suitable for interactive 3D applications. We call this system RePro3D. Our approach is based on a retro-reflective projection technology[Inami et al. 2000]. A number of images from a projector array are projected onto the retro-reflective screen. When a user looks at the screen through a half mirror, he or she, without the use of glasses, can view a 3D image that has motion parallax. We can choose the screen shape depending on the application. Image correction according to the screen shape is not required. Consequently, we can design a touch-sensitive soft screen, a complexly curved screen, or a screen with an automatically moving surface. RePro3D has a sensor function to recognize the user input. Some interactive features, such as operation of 3D objects, can be achieved by using it.

Manganese-Catalyzed Directed Methylation of C(sp2)–H Bonds at 25 °C with High Catalytic Turnover

We report here a manganese-catalyzed C-H methylation reaction of considerable substrate scope, using MeMgBr, a catalytic amount of MnCl2·2LiCl, and an organic dihalide oxidant. The reaction features ambient temperature, low catalyst loading, typically 1%, high catalytic turnover reaching 5.9 × 103, and no need for an extraneous ligand and illustrates a unique catalytic use of simple manganese salts for C-H activation, which so far has relied on catalysis by manganese carbonyls.

Twinkle: interface for using handheld projectors to interact with physical surfaces

Recently, many small pocket-size projectors have been developed. It is expected that in the near future, such projectors will be installed in portable devices. Meanwhile, intuitive interfaces that operate according to the users motion have been popular. Therefore, the interfaces that can be used for accessing information using handheld projectors have been increasingly studied [Forlines et al. 2005][Cao et al. 2007]. However, these interfaces suffer from a number of problems. Some systems need motion-tracking systems in order to measure the position of the projector. Further, the surface where image is projected are limited to plain screen like a white wall.

Transmission of existence by retro reflective projection technology using handheld projector

Our research aims to enable persons to communicate remotely with numerous participants while moving around freely in public spaces. To achieve this goal, we developed a novel remote communication system based on a mutual telexistence master-slave system. In this paper, we propose a system that transmits the operators sense of existence to the participant using retro-reflective projection technology and a handheld projector, which solves the problem of a limited sense of the surroundings. Although stereoscopic presentation by motion parallax did not occur in this study, this system was expected to give the participant a stereoscopic view via the surrogate robot using a handheld projector.