Epoxycarotenoid-mediated synthesis of abscisic acid in Physcomitrella patens implicating conserved mechanisms for acclimation to hyperosmosis in embryophytes.

Plants acclimate to environmental stress signals such as cold, drought and hypersalinity, and provoke internal protective mechanisms. Abscisic acid (ABA), a carotenoid-derived phytohormone, which increases in response to the stress signals above, has been suggested to play a key role in the acclimation process in angiosperms, but the role of ABA in basal land plants such as mosses, including its biosynthetic pathways, has not been clarified. Targeted gene disruption of PpABA1, encoding zeaxanthin epoxidase in the moss Physcomitrella patens was conducted to determine the role of endogenous ABA in acclimation processes in mosses.

The maize DWARF1 encodes a gibberellin 3-oxidase and is dual localized to the nucleus and cytosol.

The maize (Zea mays) gibberellin (GA)-deficient mutant dwarf1 (d1) displays dwarfism and andromonoecy (i.e. forming anthers in the female flower).

Arabidopsis galactinol synthase AtGolS2 improves drought tolerance in the monocot model Brachypodium distachyon.

Brachypodium distachyon (purple false brome) is a herbaceous species belonging to the grass subfamily Pooideae, which also includes major crops like wheat, barley, oat and rye. The species has been established as experimental model organism for understanding and improving cereal crops and temperate grasses. The complete genome of Bd21, the community standard line of B.

Mapping and characterization of seed dormancy QTLs using chromosome segment substitution lines in rice.

Seed dormancy--the temporary failure of a viable seed to germinate under favorable conditions--is a complex characteristic influenced by many genes and environmental factors. To detect the genetic factors associated with seed dormancy in rice, we conducted a QTL analysis using chromosome segment substitution lines (CSSLs) derived from a cross between Nona Bokra (strong dormancy) and Koshihikari (weak dormancy). Comparison of the levels of seed dormancy of the CSSLs and their recurrent parent Koshihikari revealed that two chromosomal regions-on the short arms of chromosomes 1 and 6-were involved in the variation in seed dormancy.

Molecular cloning of Sdr4, a regulator involved in seed dormancy and domestication of rice.

Seed dormancy provides a strategy for flowering plants to survive adverse natural conditions. It is also an important agronomic trait affecting grain yield, quality, and processing performance. We cloned a rice quantitative trait locus, Sdr4, which contributes substantially to differences in seed dormancy between japonica (Nipponbare) and indica (Kasalath) cultivars.

Three SnRK2 protein kinases are the main positive regulators of abscisic acid signaling in response to water stress in Arabidopsis.

Responses to water stress are thought to be mediated by transcriptional regulation of gene expression via reversible protein phosphorylation events. Previously, we reported that bZIP (basic-domain leucine zipper)-type AREB/ABF (ABA-responsive element-binding protein/factor) transcription factors are involved in ABA signaling under water stress conditions in Arabidopsis. The AREB1 protein is phosphorylated in vitro by ABA-activated SNF1-related protein kinase 2s (SnRK2s) such as SRK2D/SnRK2.

High temperature-induced abscisic acid biosynthesis and its role in the inhibition of gibberellin action in Arabidopsis seeds.

Suppression of seed germination at supraoptimal high temperature (thermoinhibiton) during summer is crucial for Arabidopsis (Arabidopsis thaliana) to establish vegetative and reproductive growth in appropriate seasons. Abscisic acid (ABA) and gibberellins (GAs) are well known to be involved in germination control, but it remains unknown how these hormone actions (metabolism and responsiveness) are altered at high temperature. Here, we show that ABA levels in imbibed seeds are elevated at high temperature and that this increase is correlated with up-regulation of the zeaxanthin epoxidase gene ABA1/ZEP and three 9-cis-epoxycarotenoid dioxygenase genes, NCED2, NCED5, and NCED9.

Dissection of the phosphorylation of rice DELLA protein, SLENDER RICE1.

DELLA proteins are repressors of gibberellin signaling in plants. Our previous studies have indicated that gibberellin signaling is derepressed by SCF(GID2)-mediated proteolysis of the DELLA protein, SLENDER RICE1 (SLR1), in rice. In addition, the gibberellin-dependent increase of phosphorylated SLR1 in the loss-of-function gid2 mutant suggests that the SCF(GID2)-mediated degradation of SLR1 might be initiated by gibberellin-dependent phosphorylation.

An important role of phosphatidic acid in ABA signaling during germination in Arabidopsis thaliana.

Phosphatidic acid (PA) functions as a lipid signaling molecule in plants. Physiological analysis showed that PA triggers early signal transduction events that lead to responses to abscisic acid (ABA) during seed germination. We measured PA production during seed germination and found increased PA levels during early germination.

Comparative genomics in salt tolerance between Arabidopsis and aRabidopsis-related halophyte salt cress using Arabidopsis microarray.

Salt cress (Thellungiella halophila), a halophyte, is a genetic model system with a small plant size, short life cycle, copious seed production, small genome size, and an efficient transformation. Its genes have a high sequence identity (90%-95% at cDNA level) to genes of its close relative, Arabidopsis. These qualities are advantageous not only in genetics but also in genomics, such as gene expression profiling using Arabidopsis cDNA microarrays.

An overview of gibberellin metabolism enzyme genes and their related mutants in rice.

To enhance our understanding of GA metabolism in rice (Oryza sativa), we intensively screened and identified 29 candidate genes encoding the following GA metabolic enzymes using all available rice DNA databases: ent-copalyl diphosphate synthase (CPS), ent-kaurene synthase (KS), ent-kaurene oxidase (KO), ent-kaurenoic acid oxidase (KAO), GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox). In contrast to the Arabidopsis genome, multiple CPS-like, KS-like, and KO-like genes were identified in the rice genome, most of which are contiguously arranged. We also identified 18 GA-deficient rice mutants at six different loci from rice mutant collections.

Genetic manipulation of gibberellin metabolism in transgenic rice.

The 'green revolution' was fueled by the introduction of the semi-dwarf trait into cereal crop cultivars. The semi-dwarf cultivars--which respond abnormally to the plant growth hormone gibberellin (GA)--are more resistant to wind and rain damage and thus yield more grain when fertilized. To generate dwarf rice plants using a biotechnological approach, we modified the level of GA by overproduction of a GA catabolic enzyme, GA 2-oxidase.

Accumulation of phosphorylated repressor for gibberellin signaling in an F-box mutant.

Gibberellin (GA) regulates growth and development in plants. We isolated and characterized a rice GA-insensitive dwarf mutant, gid2. The GID2 gene encodes a putative F-box protein, which interacted with the rice Skp1 homolog in a yeast two-hybrid assay.