UV-B signalling in rice: Response identification, gene expression profiling and mutant isolation.

Responses of rice seedlings to UV-B radiation (UV-B) were investigated, aiming to establish rice as a model plant for UV-B signalling studies. The growth of japonica rice coleoptiles, grown under red light, was inhibited by brief irradiation with UV-B, but not with blue light. The effective UV-B fluences (10 -10 μmol m ) were much lower than those reported in Arabidopsis.

Identification of anthocyanin and other flavonoids from the green-blue petals of Puya alpestris (Bromeliaceae) and a clarification of their coloration mechanism.

To understand the unique green-blue color of Puya alpestris (Bromeliaceae) flowers, we investigated their constituent anthocyanin and related compounds. An anthocyanin, two undescribed flavonols, and two flavones were isolated and identified as delphinidin 3,3',5'-tri-O-β-glucopyranoside, myricetin 3-O-[α-rhamnopyranosyl-(1 → 6)-β-glucopyranoside]-3',5'-di-O-β-glucopyranoside, myricetin 3,3',5'-tri-O-β-glucopyranoside, luteolin 4'-O-glucoside, and apigenin 4'-O-glucoside. Furthermore, the presence of chlorophyll has also been revealed.

Jasmonoyl-l-isoleucine is required for the production of a flavonoid phytoalexin but not diterpenoid phytoalexins in ultraviolet-irradiated rice leaves.

Rice produces low-molecular-weight antimicrobial compounds known as phytoalexins, in response to not only pathogen attack but also abiotic stresses including ultraviolet (UV) irradiation. Rice phytoalexins are composed of diterpenoids and a flavonoid. Recent studies have indicated that endogenous jasmonyl-l-isoleucine (JA-Ile) is not necessarily required for the production of diterpenoid phytoalexins in blast-infected or CuCl2-treated rice leaves.

Full establishment of arbuscular mycorrhizal symbiosis in rice occurs independently of enzymatic jasmonate biosynthesis.

Development of the mutualistic arbuscular mycorrhiza (AM) symbiosis between most land plants and fungi of the Glomeromycota is regulated by phytohormones. The role of jasmonate (JA) in AM colonization has been investigated in the dicotyledons Medicago truncatula, tomato and Nicotiana attenuata and contradicting results have been obtained with respect to a neutral, promotive or inhibitory effect of JA on AM colonization. Furthermore, it is currently unknown whether JA plays a role in AM colonization of monocotyledonous roots.

OsJAR1 contributes mainly to biosynthesis of the stress-induced jasmonoyl-isoleucine involved in defense responses in rice.

Jasmonate plays key roles in plant growth and stress responses, as in defense against pathogen attack. Jasmonoyl-isoleucine (JA-Ile), a major active form of jasmonates, is thought to play a pivotal role in plant defense responses, but the involvement of JA-Ile in rice defense responses, including phytoalexin production, remains largely unknown. Here we found that OsJAR1 contributes mainly to stress-induced JA-Ile production by the use of an osjar1 Tos17 mutant.

Identification of rice Allene Oxide Cyclase mutants and the function of jasmonate for defence against Magnaporthe oryzae.

Two photomorphogenic mutants of rice, coleoptile photomorphogenesis 2 (cpm2) and hebiba, were found to be defective in the gene encoding allene oxide cyclase (OsAOC) by map-based cloning and complementation assays. Examination of the enzymatic activity of recombinant GST-OsAOC indicated that OsAOC is a functional enzyme that is involved in the biosynthesis of jasmonic acid and related compounds. The level of jasmonate was extremely low in both mutants, in agreement with the fact that rice has only one gene encoding allene oxide cyclase.

AtLAZY1 is a signaling component required for gravitropism of the Arabidopsis thaliana inflorescence.

The present study identified a family of six A. thaliana genes that share five limited regions of sequence similarity with LAZY1, a gene in Oryza sativa (rice) shown to participate in the early gravity signaling for shoot gravitropism. A T-DNA insertion into the Arabidopsis gene (At5g14090) most similar to LAZY1 increased the inflorescence branch angle to 81° from the wild type value of 42°.

Identification of the gravitropism-related rice gene LAZY1 and elucidation of LAZY1-dependent and -independent gravity signaling pathways.

We identified the gene responsible for three allelic lazy1 mutations of Japonica rice (Oryza sativa L.) by map-based cloning, complementation and RNA interference. Sequence analysis and database searches indicated that the wild-type gene (LAZY1) encodes a novel and unique protein (LAZY1) and that rice has no homologous gene.

Circumnutation of rice coleoptiles: its relationships with gravitropism and absence in lazy mutants.

Although circumnutation occurs widely in higher plants, its mechanism is little understood. The idea that circumnutation is based on gravitropism has long been investigated, but the reported results have been controversial. We used dark-grown coleoptiles of rice (Oryza sativa L.

Asymmetric distribution of auxin correlates with gravitropism and phototropism but not with autostraightening (autotropism) in pea epicotyls.

The relationships between the distribution of the native auxin indole-3-acetic acid (IAA) and tropisms in the epicotyl of red light-grown pea (Pisum sativum L.) seedlings have been investigated. The distribution measurement was made in a defined zone of the third internode, using (3)H-IAA applied from the plumule as a tracer.

Toward understanding the ecological functions of tropisms: interactions among and effects of light on tropisms.

Tropisms of higher plants have been investigated for well over a century. Only recently, however, we have begun to establish their mechanisms firmly, mainly thanks to the availability of mutants and genome sequence information. For example, the starch-statolith hypothesis is now best supported as the main mechanism by which plants perceive gravity direction.

Circumnutation of rice coleoptiles: its occurrence, regulation by phytochrome, and relationship with gravitropism.

It has been found that coleoptiles of dark-grown rice (Oryza sativa L.) seedlings undergo regular circumnutation in circular orbits with periods of about 180 min. Both clockwise and counter-clockwise movements were observed, but individual coleoptiles continued to rotate only in one direction.

A novel receptor kinase involved in jasmonate-mediated wound and phytochrome signaling in maize coleoptiles.

We identified a gene of maize (Zea mays L.) that is transcriptionally activated in decapitated coleoptiles. The amino acid sequence deduced from its full-length cDNA indicated that the identified gene encodes a novel leucine-rich-repeat receptor-like kinase.

The Rice COLEOPTILE PHOTOTROPISM1 gene encoding an ortholog of Arabidopsis NPH3 is required for phototropism of coleoptiles and lateral translocation of auxin.

We isolated a mutant, named coleoptile phototropism1 (cpt1), from gamma-ray-mutagenized japonica-type rice (Oryza sativa). This mutant showed no coleoptile phototropism and severely reduced root phototropism after continuous stimulation. A map-based cloning strategy and transgenic complementation test were applied to demonstrate that a NPH3-like gene deleted in the mutant corresponds to CPT1.

Phytochrome-mediated transcriptional up-regulation of ALLENE OXIDE SYNTHASE in rice seedlings.

Allene oxide synthase (AOS) is a key enzyme for the biosynthesis of jasmonic acid (JA). We identified four AOS gene homologs, named OsAOS1-4, in the database of a japonica rice genome and cloned a full-length cDNA of OsAOS1. The analysis of deduced amino acid sequences indicated that only OsAOS1 has a chloroplast transit peptide among all the identified monocot AOSs including OsAOSs.

Photomorphogenesis of rice seedlings: a mutant impaired in phytochrome-mediated inhibition of coleoptile growth.

A mutant showing a long coleoptile phenotype under white light was isolated from gamma-ray-mutagenized rice (cv. Nihonmasari). This mutant, named cpm1 (coleoptile photomorphogenesis 1), has been found to be impaired in phytochrome-mediated inhibition of coleoptile growth.