Chemical aspects of the circadian leaf movement known as nyctinasty are discussed in this article. Each of nyctinastic plants of five different genera so far examined contained a pair of factors, one of which induces leaf closure and another induces leaf opening. The relative contents of the closing and opening factors changed correlating with the nyctinastic leaf movement. We focused on the leaf-closing chemical factor, jasmonic acid glucoside (JAG), for bioorganic studies on nyctinasty in Samanea saman. Use of fluorescence-labeled and photoaffinity-labeled factors revealed that JAG targeted extensor motor cells in pulvinus and bound to a membrane target protein on the cells. Another function of JAG as a trap-closing chemical factor of Dionaea muscipula is also described.

Plants responses to internal signals and environmental stimuli are regulated by a complex mechanism of signal transduction networks. Plant hormones are important signal mediators that play key roles in signaling. Brassinosteroids (BRs) and jasmonic acid (JA) are plant hormones involved in plant development and defense responses to environmental stress. To explore the biological functions of their biosynthetic pathways, we conducted a systematic search for specific inhibitors of BRs biosynthesis and JA biosynthesis. The BRs biosynthesis inhibitors were developed based on the molecular scaffold of P450 inhibitors. Structure-activity relationship studies created YCZ-18, which is the most potent BRs biosynthesis inhibitor found to date. Development of the JA biosynthesis inhibitors was conducted based on the design of inhibitors targeting allene oxide synthase (AOS, CYP74A), a key enzyme of JA biosynthesis. This strategy led to the discovery of JM-8686, the first synthetic inhibitor of JA biosynthesis.

A naturally occurring auxin, indole-3-acetic acid (IAA) regulates diverse physiological processes in plants. We have studied the biochemical role for the YUCCA (YUC) family of flavin monooxygenases in IAA biosynthesis in Arabidopsis. We uncovered TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA)-mediated indole-3-pyruvic acid (IPA) pathway and placed the YUC family in this pathway. Our study elucidated the complete IAA biosynthesis pathway, in which TAAs first convert tryptophan to IPA and YUCs subsequently catalyze oxidative decarboxylation of IPA to IAA. Here we summarize the studies on biochemical and physiological functions of YUC.

Developmental process, growth and breeding season of most living organisms are controlled by photoperiods of their living environment. The phenomenon common to a variety of organisms is well-known as "photoperiodism". The report written by Garner and Allard of the United States Department of Agriculture based on a series of studies almost 100 years ago is thought to be the 1^<st> research article on the photoperiodism. What kind of questions did Garner and Allard address 100 years ago? Have all the questions solved by studies with most advanced science and technology since then? In this special issue, four research groups working on photoperiodic flowering have summarized recent progresses, focusing on 9 research topics. We hope that our reports will be helpful for young researchers who will challenge some unsolved questions on the photoperiodic flowering.

Circadian clock has been shown to affect photoperiodic flowering of many plant species such as Arabidopsis thaliana (Arabidopsis) and Oryza sativa.LATE ELONGATED HYPOCOTYL (LHY), CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), EARLY FLOWERING 3 (ELF3) and CRYPTOCHROME 2 (CRY2) play key roles in the control of circadian rhythms of Arabidopsis. lhy;cca1, elf3;cry2 and elf3;sel1001 appear to have some characteristics of the short-day plants. In this short review, we show a recent progress on characterization of Arabidopsis mutants of circadian clock genes mainly based on our recent studies.

Chrysanthemum is a typical short-day plant and responds to shortening of daylength in the transition from vegetative to reproductive phase. The manipulation of daylength is widely used in the commercial production of chrysanthemum. In chrysanthemum, daylength and growth temperature affect the development of floral organs after the floral transition. Recent advances in molecular genetics have identified a florigen in model plants. Recently, an antiflorigen which inhibits flowering antagonizing with florigen has been found in chrysanthemum. This review summarizes the flowering regulated by daylength and temperature through the balance of florigen and antifl origen production in chrysanthemum.

Recent molecular genetic analyses revealed a general outline of the genetic network in photoperiodic flowering in rice. There are two florigen genes termed Hd3a and RFT1 tandemly arranged in the rice genome functions as molecular switches for floral transition in rice. According to the difference in transcriptional machinery for these genes and in genetic background in rice varieties, some rice varieties behave as an absolute short-day plant, and other varieties behave as a facultative short-day plant. Here, this review focused on what molecular mechanisms are underlying to confer the distinct photoperiodic responses of flowering.

Plants regulate timing of phase transition in response to day length. Over the past 80 years a considerable number of studies have been done on photoreceptors and circadian clock to understand photoperiodism. Today, the factors mediating the physiological response have been examined extensively. However we could not achieve a comprehensive understanding yet, due to their complexity of signaling network. This review provides a brief overview of the current state of photoreceptors, circadian clock and photoperiodic flowering in Arabidopsis thaliana and addresses to the future issues of these research fields. Also we introduce a novel approach to understand a framework of entire signaling pathway from light input to physiological output by using species with low genetic redundancy. In particular, recent studies in the liverwort Marchantia polymorpha, one of emerging model plants in bryophytes, have revealed that it has the most simplified version with all required components for A. thaliana circadian clock and photoperiodic growth-phase regulation. Together with the phylogenetic position as basal land plants, studies with M. polymorpha provide us insights into the evolution of underlying mechanism regulating photoperiodic growth-phase transition.

The goal of crop breeding is to develop crop varieties that stably provide as much agricultural products as possible with qualities meeting consumer needs. In practice, genetic modifications (crossing, mutational and transgenic breeding) and selections have been intensively performed to enhance tolerance or resistance for abiotic or biotic stresses that impair stable production of crops in addition to improvement of yields and qualities. Physiological effects of phytohormones on crops have been studied for a long time. Chemicals showing hormonal activity or affecting hormone metabolism or signaling are widely used as plant growth regulators in agriculture. Recent advances in plant molecular genetics and genomics have revealed that a number of agriculturally important traits are closely related to phytohormones. This review introduces several hormone-related traits and corresponding molecular mechanisms. We summarize recent and future possible contributions of hormone research to crop breeding.

Several parasitic plants in Orobanchaceae, such as Striga and Orobanche, cause devastating damage on agriculture worldwide. However, the molecular mechanisms of plant parasitism remain poorly understood. Orobanchaceae include species in a different range of parasitism, i.e. facultative and obligate parasites. Facultative parasites complete their life cycle without host plants, while obligate parasites are not able to survive without hosts in a natural condition. Although both parasites respond to quinone signals to develop infectious organs called haustoria, their shapes are distinct. Their responses to germination stimulants are also different. We are conducting genome and transcriptome analyses of an obligate parasite Striga asiatica and a facultative parasite Phtheirospermum japonicum to identify genes responsible for plant parasitism. A transformation protocol of P. japonicum was also established and used for functional characterization of parasitic plant genes.

Transport is an important factor that determines endogenous concentrations of a compound in association with biosynthesis and catabolism. However, our understanding on the molecular mechanisms for transport is limited compared to those for biosynthesis and catabolism. We recently developed a modified yeast two-hybrid system to functionally screen transporters for the plant hormone abscisic acid (ABA). Here we describe our strategy for identification of ABA transporters and discuss how we can apply the strategy to identify transporters of other compounds.

Plant factory is a plant production system where the cultivation space is isolated from outside. The environmental factors for plant growth are artificially controlled and the plant production can be performed through the year in the plant factory. Total amount of vegetable production, which have a feature of non-agricultural chemicals, and stable production and uniformity in size and shape, in plant factories is getting increased. On the other hand, research for producing the raw materials for pharmaceuticals and cosmetics has been attempted, and some results were achieved. This article describes the current status and the future challenges of plant factory.