Involvement of cinnamyl-alcohol dehydrogenase in the control of lignin formation in Sorghum bicolor L. Moench

The lignin structure and enzyme activities of normal and brown-midrib (BMR-6) mutant lines of Sorghum bicolor have been compared to identify the enzyme(s) involved in the reduction of the lignin content of the mutant. The results indicate that cinnamyl-alcohol dehydrogenase (CAD) and caffeic acid O-methyltransferase are depressed in the BMR-6 line, whereas the structural modifications correspond only to a reduction of CAD activity. Apparently, the change in the Sorghum lignin content, caused by depression of CAD activity, is accompanied by the incorporation of cinnamaldehydes into the core lignin.Abbreviations CAD cinnamyl-alcohol dehydrogenase - HPLC high-performance liquid chromatography - m/z mass number - OMT caffeic acid O-methyltransferase     

Association of lignin and <Emphasis Type="Italic">FLEXIBLE CULM 1 (FC1)</Emphasis> ortholog in imparting culm strength and lodging resistance in kodo millet (<Emphasis Type="Italic">Paspalum scrobiculatum</Emphasis> L.)

To understand the lodging behavior in kodo millet (Paspalum scrobiculatum L.) at morphological, biochemical, and molecular levels, 22 germplasm accessions selected based on previous trials were characterized for culm strength-related morphological traits such as pulling force, culm weight per unit length, culm diameter, recovery angle after bending and degree of lodging, and biochemical traits such as cellulose, hemicellulose, and lignin content of the culm. Correlation among traits and path analysis with degree of lodging showed that only lignin content per unit length of the culm had a very high negative effect on degree of lodging, followed by culm diameter, which means that higher the lignin content and culm diameter, the lesser will be the degree of lodging. Hence, it was concluded that any improvement for lodging resistance in kodo millet can be achieved through improving the lignin content (mg/cm of the dry culm) and culm diameter. Gene expression studies in kodo millet for FLEXIBLE CULM 1 (FC1), a gene implicated in lignin biosynthetic pathway and lodging resistance in rice, suggests the role of FC1 gene ortholog in lignin accumulation in kodo millet as well. Accordingly, the highest gene expression was recorded in strong culm line “Adari” a land race and the lowest expression in “Aamo 10,” a weak culm line.     

<Emphasis Type="Italic">pgd1</Emphasis>, an <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> deletion mutant,is defective in pollen germination

An Arabidopsis deletion mutant was fortuitously identified from the alpha population of T-DNA insertional mutants generated at the University of Wisconsin Arabidopsis Knockout Facility. Segregation and reciprocal crosses indicated that the mutant was a gametophytic pollen sterile mutant. Pollen carrying the mutation has the unusual phenotype that it is viable, but cannot germinate. Thus, the mutant was named pollen germination defective mutant 1 (pgd1), based on the pollen phenotype. Flanking sequences of the T-DNA insertion in the pgd1 mutant were identified by thermal asymmetric interlaced (TAIL) PCR. Sequencing of bands from TAIL PCR revealed that the T-DNA was linked to the gene XLG1, At2g23460, at its downstream end, while directly upstream of the T-DNA was a region between At2g22830 and At2g22840, which was 65 genes upstream of XLG1. Southern blotting and genomic PCR confirmed that the 65 genes plus part of XLG1 were deleted in the pgd1 mutant. A 9,177 bp genomic sequence containing the XLG1 gene and upstream and downstream intergenic regions could not rescue the pgd1 pollen phenotype. One or more genes from the deleted region were presumably responsible for the pollen germination defect observed in the pgd1 mutant. Because relatively few mutations have been identified that affect pollen germination independent of any effect on pollen viability, this mutant line provides a new tool for identification of genes specifically involved in this phase of the reproductive cycle.     

Rice <Emphasis Type="Italic">phot1a</Emphasis> mutation reduces plant growth by affecting photosynthetic responses to light during early seedling growth

The aim of this work was to characterize the phot1 mutant of rice during early seedling growth in various light conditions. We isolated the rice T-DNA insertion mutant phot1a-1 and compared it to the Tos17 insertion mutant phot1a-2. When phot1a mutants were grown under WL (100) and BL (40 μmol m⁻² s⁻¹), they demonstrated a considerable reduction in photosynthetic capacity, which included decreased leaf CO₂ uptake and plant growth. Pigment analysis showed no significant difference between wild-type and mutants in the Chl a:b ratios, whereas in the latter, total concentration was reduced (a 2-fold decrease). Carotenoid contents of the mutants were also decreased considerably, implying the involvement of phot1a in pigment degradation. Deletion of phot1a showed higher contents of H₂O₂ in leaves. Chloroplastic APX and SOD activities were lower in the mutants whereas the activities of cytosolic enzymes were increased. Immunoblotting indicated reduced accumulation of photosystem proteins (D1, D2, CP43, Lhca2, and PsaC) relative to the other light-harvesting complexes in the mutant. We conclude that the defect of Os Phot1a affects degradation of chlorophylls and carotenoids, and under photosynthetically active photon fluxes, mutation of phot1a results in loss of photosynthetic capacity owing to the damage of photosystems caused by elevated H₂O₂ accumulation, leading to a reduction in plant growth. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Characterization of <Emphasis Type="Italic">Glossy1</Emphasis>-homologous genes in rice involved in leaf wax accumulation and drought resistance

The outermost surfaces of plants are covered with an epicuticular wax layer that provides a primary waterproof barrier and protection against different environmental stresses. Glossy 1 (GL1) is one of the reported genes controlling wax synthesis. This study analyzed GL1-homologous genes in Oryza sativa and characterized the key members of this family involved in wax synthesis and stress resistance. Sequence analysis revealed 11 homologous genes of GL1 in rice, designated OsGL1-1 to  OsGL1-11. OsGL1-1, -2 and -3 are closely related to GL1. OsGL1-4, -5, -6, and -7 are closely related to Arabidopsis CER1 that is involved in cuticular wax biosynthesis. OsGL1-8, -9, -10 and -11 are closely related to SUR2 encoding a putative sterol desaturase also involved in epicuticular wax biosynthesis. These genes showed variable expression levels in different tissues and organs of rice, and most of them were induced by abiotic stresses. Compared to the wild type, the OsGL1-2-over-expression rice exhibited more wax crystallization and a thicker epicuticular layer; while the mutant of this gene showed less wax crystallization and a thinner cuticular layer. Chlorophyll leaching experiment suggested that the cuticular permeability was decreased and increased in the over-expression lines and the mutant, respectively. Quantification analysis of wax composition by GC–MS revealed a significant reduction of total cuticular wax in the mutant and increase of total cuticular wax in the over-expression plants. Compared to the over-expression and wild type plants, the osgl1-2 mutant was more sensitive to drought stress at reproductive stage, suggesting an important role of this gene in drought resistance. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Knockout of a starch synthase gene <Emphasis Type="Italic">OsSSIIIa</Emphasis>/<Emphasis Type="Italic">Flo5</Emphasis> causes white-core floury endosperm in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

To elucidate the role of SSIIIa during starch synthesis in rice (Oryza sativa L.) endosperm, we characterized null mutants of this gene, generated by T-DNA insertions. Scanning electron microscope (SEM) analysis revealed that the starch granules in these mutants are smaller and rounder compared with the wild type controls, and that the mutant endosperm is characterized by a loosely packed central portion exhibiting a floury-like phenotype. Hence, the OsSSIIIa (Oryza sativa SSIIIa) mutations are referred to as white-core floury endosperm 5-1 (flo5-1) and flo5-2. Based upon their X-ray diffraction patterns, the crystallinity of the starch in the flo5 mutant endosperm is decreased compared with wild type. Through determination of the chain-length distribution of the mutant endosperm starch, we found that flo5-1 and flo5-2 mutants have reduced the content of long chains with degree of polymerization (DP) 30 or greater compared with the controls. This suggests that OsSSIIIa/Flo5 plays an important role in generating relatively long chains in rice endosperm. In addition, DP 6 to 8 and DP 16 to 20 appeared to be reduced in endosperm starch of flo5-1 and flo5-2, whereas DP 9 to 15 and DP 22 to 29 were increased in these mutants. By the use of differential scanning calorimetry (DSC), the gelatinization temperatures of endosperm starch were found to be 1–5°C lower than those of the control. We propose a distinct role for OsSSIIIa/Flo5 and the coordinated action of other SS isoforms during starch synthesis in the seed endosperm of rice.     

Identification and fine mapping of a thermo-sensitive chlorophyll deficient mutant in rice (<Emphasis Type="Italic">Oryza sativa </Emphasis>L.)

A thermo-sensitive chlorophyll deficient mutant was isolated from more than 15,000 transgenic rice lines. The mutant displayed normal phenotype at 23°C or lower temperature (permissive temperature). However, when grown at 26°C or higher (nonpermissive temperature) the plant exhibited an abnormal phenotype characterized by yellow green leaves. Genetic analysis revealed that a single nuclear-encoded recessive gene is responsible for the mutation, which is tentatively designed as cde1(t) (chlorophyll deficient 1, temporally). PCR analysis and hygromycin resistance assay indicated the mutation was not caused by T-DNA insertion. To isolate the cde1(t) gene, a map-based cloning strategy was employed and 15 new markers (five SSR and ten InDels markers) were developed. A high-resolution physical map of the chromosomal region around the cde1(t) gene was made using F₂ and F₃ population consisting of 1,858 mutant individuals. Finally, the cde1(t) gene was mapped in 7.5 kb region between marker ID10 and marker ID11 on chromosome 2. Sequence analysis revealed only one candidate gene, OsGluRS, in the 7.5 kb region. Cloning and sequencing of the target region from the cde1(t) mutant showed that a missense mutation occurred in the mutant. So the OsGluRS gene (TIGR locus Os02 g02860) which encode glutamyl-tRNA synthetase was identified as the Cde1(t) gene.     

Both caffeoyl Coenzyme A 3-<Emphasis Type="Italic">O</Emphasis>-methyltransferase 1 and caffeic acid <Emphasis Type="Italic">O</Emphasis>-methyltransferase 1 are involved in redundant functions for lignin,flavonoids and sinapoyl malate biosynthesis in Arabidopsis

Two methylation steps are necessary for the biosynthesis of monolignols, the lignin precursors. Caffeic acid O-methyltransferase (COMT) O-methylates at the C5 position of the phenolic ring. COMT is responsible for the biosynthesis of sinapyl alcohol, the precursor of syringyl lignin units. The O-methylation at the C3 position of the phenolic ring involves the Caffeoyl CoA 3-O-methyltransferase (CCoAOMT). The CCoAOMT 1 gene (At4g34050) is believed to encode the enzyme responsible for the first O-methylation in Arabidopsis thaliana. A CCoAOMT1 promoter-GUS fusion and immunolocalization experiments revealed that this gene is strongly and exclusively expressed in the vascular tissues of stems and roots. An Arabidopsis T-DNA null mutant named ccomt 1 was identified and characterised. The mutant stems are slightly smaller than wild-type stems in short-day growth conditions and has collapsed xylem elements. The lignin content of the stem is low and the S/G ratio is high mainly due to fewer G units. These results suggest that this O-methyltransferase is involved in G-unit biosynthesis but does not act alone to perform this step in monolignol biosynthesis. To determine which O-methyltransferase assists CCoAOMT 1, a comt 1 ccomt1 double mutant was generated and studied. The development of comt 1 ccomt1 is arrested at the plantlet stage in our growth conditions. Lignins of these plantlets are mainly composed of p-hydroxyphenyl units. Moreover, the double mutant does not synthesize sinapoyl malate, a soluble phenolic. These results suggest that CCoAOMT 1 and COMT 1 act together to methylate the C3 position of the phenolic ring of monolignols in Arabidopsis. In addition, they are both involved in the formation of sinapoyl malate and isorhamnetin.     

Isolation,expression, and evolution analysis of the type 2C protein phosphatase gene <Emphasis Type="Italic">BcABI1</Emphasis> involved in abiotic and biotic stress in <Emphasis Type="Italic">Brassica campestris</Emphasis> ssp. <Emphasis Type="Italic">chinensis</Emphasis>

Dense plant cultivation is an efficient approach to utilize the maximum inputs for increasing maize production. However, dense plant populations may prone to lodging as it results in increased plant height and reduced culm diameter; therefore, we hypothesized that weaker stems may be responsible for maize lodging. In this study, we examined the regulatory effects of paclobutrazol under two commonly used application methods (seed-soaking and seed-dressing). Seed-soaking with paclobutrazol at the rate of 0 (CK1), 200 (S1), 300 (S2), and 400 (S3) mg L^?1, while seed-dressing at the rate of 0 (CK2), 1.5 (D1), 2.5 (D2), and 3.5 (D3) g kg^?1 were used. Results showed that paclobutrazol improved the culm physical strength by increasing the rind penetration strength, stalk breaking strength, culm diameter, wall thickness, and dry weight per unit length of basal third internode, compared to control plants. Moreover, paclobutrazol reduced the internode length, plant height, ear height, center of gravity height and lodging rate in both growing seasons. In addition, more lignin was accumulated in the basal internode and the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD) and 4-coumarate: CoA ligase (4CL) increased with paclobutrazol, and their maximum values were observed in the S2 and D3 treatments, resulting in strong lodging resistance. Lignin content was positively and significantly correlated with the rind penetration strength, breaking strength of internode, and activities of PAL, 4CL, POD, and CAD, while significantly and negatively correlated with lodging percentage. The present findings suggested that 300 mg L^?1 and 3.5 g kg^?1 of paclobutrazol may efficiently be utilized to minimize the risk of lodging, not only by manipulating plant height but also by enhancing culm physical strength and lignin accumulation in basal internodes.     

<Emphasis Type="Italic">NARROW LEAF 7</Emphasis> controls leaf shape mediated by auxin in rice

Elucidation of the genetic basis of the control of leaf shape could be of use in the manipulation of crop traits, leading to more stable and increased crop production. To improve our understanding of the process controlling leaf shape, we identified a mutant gene in rice that causes a significant decrease in the width of the leaf blade, termed narrow leaf 7 (nal7). This spontaneous mutation of nal7 occurred during the process of developing advanced backcrossed progeny derived from crosses of rice varieties with wild type leaf phenotype. While the mutation resulted in reduced leaf width, no significant morphological changes at the cellular level in leaves were observed, except in bulliform cells. The NAL7 locus encodes a flavin-containing monooxygenase, which displays sequence homology with YUCCA. Inspection of a structural model of NAL7 suggests that the mutation results in an inactive enzyme. The IAA content in the nal7 mutant was altered compared with that of wild type. The nal7 mutant overexpressing NAL7 cDNA exhibited overgrowth and abnormal morphology of the root, which was likely to be due to auxin overproduction. These results indicate that NAL7 is involved in auxin biosynthesis. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under accession numbers AB354301 and AB354302.     

Genomic targeting and mapping of tiller inhibition gene (<Emphasis Type="Italic">tin3</Emphasis>) of wheat using ESTs and synteny with rice

Changes in plant architecture have been central to the domestication of wild species. Tillering or the degree of branching determines shoot architecture and is a key component of grain yield and/or biomass. Previously, a tiller inhibition mutant with monoculm phenotype was isolated and the mutant gene (tin3) was mapped in the distal region of chromosome arm 3A^mL of Triticum monococcum. As a first step towards isolating a candidate gene for tin3, the gene was mapped in relation to physically mapped expressed sequence tags (ESTs) and sequence tag site (STS) markers developed based on synteny with rice. In addition, we investigated the relationship of the wheat region containing tin3 with the corresponding region in rice by comparative genomic analysis. Wheat ESTs that had been previously mapped to deletion bins provided a useful framework to identify closely related rice sequences and to establish the most likely syntenous region in rice for the wheat tin3 region. The tin3 gene was mapped to a 324-kb region spanned by two overlapping bacterial artificial chromosomes (BACs) of rice chromosome arm 1L. Wheat–rice synteny was exceptionally high at the tin3 region despite being located in the high-recombination, gene-rich region of wheat. Identification of tightly linked flanking EST and STS markers to the tin3 gene and its localization to highly syntenic rice BACs will assist in the future development of a high-resolution map and map-based cloning of the tin3 gene. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

<Emphasis Type="Italic">Dwarf 88</Emphasis>, a novel putative esterase gene affecting architecture of rice plant

Rice architecture is an important agronomic trait that affects grain yield. We characterized a tillering dwarf mutant d88 derived from Oryza sativa ssp. japonica cultivar Lansheng treated with EMS. The mutant had excessive shorter tillers and smaller panicles and seeds compared to the wild-type. A reduction in number and size of parenchyma cells around stem marrow cavity as well as a delay in the elongation of parenchyma cells caused slender tillers and dwarfism in the d88 mutant. The D88 gene was isolated via map-based cloning and identified to encode a putative esterase. The gene was expressed in most rice organs, with especially high levels in the vascular tissues. The mutant carried a nucleotide substitution in the first exon of the gene that led to the substitution of arginine for glycine, which presumably disrupted the functionally conserved N-myristoylation domain of the protein. The function of the gene was confirmed by complementation test and antisense analysis. D88, thus, represents a new category of genes that regulates cell growth and organ development and consequently plant architecture. The potential relationship between the tiller formation associated genes and D88 is discussed and future identification of the substrate for D88 may lead to the characterization of new pathways regulating plant development. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Isolation and characterization of <Emphasis Type="Italic">shs1</Emphasis>, a sugar-hypersensitive and ABA-insensitive mutant with multiple stress responses

To identify salt tolerance determinants, we screened for double mutants from a T-DNA tagged sos3-1 mutant population in the Arabidopsis Col-0 gl1 background. The shs1-1 (sodium hypersensitive) sos3-1 mutant was isolated as more sensitive to NaCl than sos3-1 plants. TAIL-PCR revealed that the introduced T-DNA was located 62 bp upstream of the initiation codon of an adenylate translocator-like protein gene on chromosome IV. SHS1 mRNA did not accumulate in shs1-1 sos3-1 plants although it accumulated in shoots of both sos3-1 and the wild type plants, indicating that this gene is inactive in the mutant. Genetic co-linkage analysis revealed that the mutation causing the phenotype segregated as a recessive, single gene mutation. This mutant showed altered sensitive responses to salt as well as to cold stress. It also demonstrated sugar sensitive and ABA insensitive phenotypes including enhanced germination, reduced growth, altered leaf morphology, and necrosis on leaves at an early growth stage. Sensitivity of sos3-1 shs1-1 root growth to LiCl, KCl, and mannitol was not significantly different from growth of sos3-1 roots. Further, expression of 35S::SHS1 in sos3-1 shs1-1 plants complemented NaCl and sugar sensitivity and partially restored the leaf morphology. G. Inan and F. Goto contributed equally in this work.     

New target for rice lodging resistance and its effect in a typhoon

We demonstrated the new target for lodging resistance in rice (Oryza sativa L.) by the analysis of physiological function of a locus for lodging resistance in a typhoon (lrt5) with the near isogenic line under rice “Koshihikari” genetic background (tentatively named S1). The higher lodging resistance of S1 was observed during a typhoon in September 2004 (28 days after heading), when most other plants in “Koshihikari” became lodged. Visual observations showed that bending of the upper stems triggered lodging during the typhoon; the upper stem of “Koshihikari” buckled completely, whereas that of S1 remained straight. In addition to the strong rain and winds during the typhoon, the weight of the buckled upper plant parts increased the pressure on adjacent plants and caused a domino effect in “Koshihikari”. Young’s modulus, an indicator of the rigidity of the culm, was significantly higher in S1 than in “Koshihikari”. In the upper culm, the starch content in S1 was 4.8 times the value in “Koshihikari”, and senescence was delayed in the upper leaves of S1. These results suggest that the rigidity of the upper culm by the higher starch content (as a result of delayed senescence in the upper leaves) may be responsible for the higher lodging resistance during a typhoon in rice. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Evidence for a role of AtCAD 1 in lignification of elongating stems of Arabidopsis thaliana

The cinnamyl alcohol dehydrogenase (AtCAD) multigene family in Arabidopsis is composed of nine genes. Our previous studies focused on the two isoforms AtCAD C and AtCAD D which show a high homology to those related to lignification in other plants. This study focuses on the seven other Arabidopsis CAD for which functions are not yet elucidated. Their expression patterns were determined in different parts of Arabidopsis. Only CAD 1 protein can be detected in elongating stems, flowers, and siliques using Western-blot analysis. Tissue specific expression of CAD 1, B1, and G genes was determined using their promoters fused to the GUS reporter gene. CAD 1 expression was observed in primary xylem in accordance with a potential role in lignification. Arabidopsis T-DNA mutants knockout for the different genes CAD genes were characterized. Their stems displayed no substantial reduction of CAD activities for coniferyl and sinapyl alcohols as well as no modifications of lignin quantity and structure in mature inflorescence stems. Only a small reduction of lignin content could be observed in elongating stems of Atcad 1 mutant. These CAD genes in combination with the CAD D promoter were used to complement a CAD double mutant severely altered in lignification (cad c cad d). The expression of AtCAD A, B1, B2, F, and G had no effect on restoring a normal lignin profile of this mutant. In contrast, CAD 1 complemented partly this mutant as revealed by the partial restoration of conventional lignin units and by the decrease in the frequency of β-O-4 linked p-OH cinnamaldehydes.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

A role of <Emphasis Type="Italic">OsGA20ox1</Emphasis>, encoding an isoform of gibberellin 20-oxidase,for regulation of plant stature in rice

Gibberellin (GA) 20-oxidase (GA20ox) is a key enzyme that normally catalyzes the penultimate steps in GA biosynthesis. One of the GA20ox genes in rice (Oryza sativaL.), OsGA20ox2 (SD1), is well known as the Green Revolution gene, and loss-of function mutation in this locus causes semi-dwarfism. Another GA20ox gene, OsGA20ox1, has also been identified, but its contribution to plant stature has remained unclear because no suitable mutants have been available. We isolated a mutant, B142, tagged with a T-DNA containing three CaMV 35S promoters, which showed a tall, GA-overproduction phenotype. The final stature of the B142 mutant reflects internode overgrowth and is approximately twice that of its wild-type parent. This mutant responds to application of both GA3 and a GA biosynthesis inhibitor, indicating that it is a novel tall mutant of rice distinct from GA signaling mutants such as slr1. The integrated T-DNAs, which contain three CaMV 35S promoters, are located upstream of the OsGA20ox1 open reading frame (ORF) in the B142 mutant genome. Analysis of mRNA and the endogenous GAs reveal that biologically active GA level is increased by up-regulation of the OsGA20ox1 gene in B142. Introduction of OsGA20ox1 cDNA driven by 35S promoter into the wild type phenocopies the morphological characteristics of B142. These results indicate that the elongated phenotype of the B142 mutant is caused by up-regulation of the OsGA20ox1 gene. Moreover, the final stature of rice was reduced by specific suppression of the OsGA20ox1 gene expression. This result indicates that not only OsGA20ox2 but also OsGA20ox1 affects plant stature.     

T-DNA tagged knockout mutation of rice <Emphasis Type="Italic">OsGSK1</Emphasis>, an orthologue of <Emphasis Type="Italic">Arabidopsis BIN2</Emphasis>, with enhanced tolerance to various abiotic stresses

T-DNA-tagged rice plants were screened under cold- or salt-stress conditions to determine the genes involved in the molecular mechanism for their abiotic-stress response. Line 0-165-65 was identified as a salt-responsive line. The gene responsible for this GUS-positive phenotype was revealed by inverse PCR as OsGSK1 (O ryza s ativa g lycogen s ynthase k inase3-like gene 1), a member of the plant GSK3/SHAGGY-like protein kinase genes and an orthologue of the Arabidopsis b rassinosteroid in sensitive 2 (BIN2), AtSK21. Northern blot analysis showed that OsGSK1 was most highly detected in the developing panicles, suggesting that its expression is developmental stage specific. Knockout (KO) mutants of OsGSK1 showed enhanced tolerance to cold, heat, salt, and drought stresses when compared with non-transgenic segregants (NT). Overexpression of the full-length OsGSK1 led to a stunted growth phenotype similar to the one observed with the gain-of-function BIN/AtSK21 mutant. This suggests that OsGSK1 might be a functional rice orthologue that serves as a negative regulator of brassinosteroid (BR)-signaling. Therefore, we propose that stress-responsive OsGSK1 may have physiological roles in stress signal-transduction pathways and floral developmental processes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Serry Koh and Sang-Choon Lee are co-first authors.