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Plant hormones are small organic molecules that influence almost every aspect of plant growth and development. Genetic and molecular studies have revealed a large number of genes that are involved in responses to numerous plant hormones, including auxin, gibberellin, cytokinin, abscisic acid, ethylene, jasmonic acid, salicylic acid, and brassinosteroid. Here, we develop an Arabidopsis hormone database, which aims to provide a systematic and comprehensive view of genes participating in plant hormonal regulation, as well as morphological phenotypes controlled by plant hormones. Based on data from mutant studies, transgenic analysis and gene ontology (GO) annotation, we have identified a total of 1026 genes in the Arabidopsis genome that participate in plant hormone functions. Meanwhile, a phenotype ontology is developed to precisely describe myriad hormone-regulated morphological processes with standardized vocabularies. A web interface (http://ahd.cbi.pku.edu.cn) would allow users to quickly get access to information about these hormone-related genes, including sequences, functional category, mutant information, phenotypic description, microarray data and linked publications. Several applications of this database in studying plant hormonal regulation and hormone cross-talk will be presented and discussed.

Gibberellins (GAs) play important roles in many essential plant growth and development processes. A family of nuclear growth-repressing DELLA proteins is the key component in GA signaling. GA perception is mediated by GID1, and the key event of GA signaling is the degradation of DELLA proteins via the 26S proteasome pathway. DELLA proteins integrating other plant hormones signaling and environmental cue modulating plant growth and development have been revealed. GA turning on the de-DELLA-repressing system is conserved, and independently establishes step-by-step recruitment of GA-stimulated GID1-DELLA interaction and DELLA growth-repression functions during land plant evolution. These discoveries open new prospects for the understanding of GA action and DELLA-mediated signaling in plants.

Dominant Semidwarf mutant rice (Sdd) was obtained from its wild type (WT) by irradiation with a low-energy ion beam. Six tall revertants of Sdd were induced by irradiation. The revertants restored the plant height to that of WT plants. Investigation of the agronomic character and genetic analysis indicate that the revertants are similar to WT plants with putative different inherited mutations. The revertants were checked for DNA differences using the simple sequence repeat technique. Among 408 such primers used, only 2 primers detected mutation sites in the revertants, which provided the molecular evidence for the revertants induced from Sdd. This study indicates that ion irradiation may be used as a mutagen to create revertants for plant architecture studies and could be a new application.

By nitrogen ion implanting, we obtained a semi-dwarf mutant from a japonica rice cultivar Y98148, designated as Y98149. The genetic analysis of Y98149 indicated that the semi-dwarf phenotype was controlled by a single dominant gene, Sdd(t). We show that Y98149 reduced plant height mainly via inhibiting the first, second and third internode elongation. Based on this dwarfing pattern, the mutant could be grouped into dn-type dwarf defined by Takeda [Gamma Field Symp. (1977) Vol. 16, PP. 1-18]. In addition, the Sdd(t) gene was sensitive to gibberellin (GA) based on the response to extraneous GA 3 and the quantitative determination of endogenous GA 1 and GA 4 . To map the Sdd(t) gene, we tested molecular markers by bulk segregant analysis. The Sdd(t) gene was localized to a 6.4 cM-interval on the short arm of chromosome 6, flanked by two sequence-tagged site markers S9 and S 13.

Phytohormone gibberellins (GA) are a large family of tetracyclic diterpenoids and play the important roles in modulation of plant growth and development throughout the plant life cycle. GA depresses its signaling by the GA-promoted destabilization of the DELLA protein growth repressors via 26S proteasome pathway. Recent evidences indicate that the DELLA proteins interact with multiple environmental and other hormonal response pathways and confer plant growth restraint. Furthermore, the discovery of rice GIBBERELLIN INSENSITIVE DWARF1 (GID1) and three Arabidopsis AtGID1 homologs as soluble GA receptors opens new prospects for understanding of de-DELLA repressing system in GA signaling.

Substantial increases in grain yield of cereal crops are required to feed a growing human population. Here we show that a natural variant of SEMIDWARF AND HIGH-TILLERING (SDT) increases harvest index and grain productivity in rice. Gain-of-function sdt mutation has a shortened polyadenylation tail on the OsmiR156h microRNA precursor, which cause the up-regulation of OsmiR156h. The plants carrying the semidominant sdt allele exhibit reduced plant height, enhanced lodging resistance, increased tiller numbers per plant, and resulting in an increased grain yield. We also show that combining the sdt allele with the OsSPL14WFP allele can be effective in simultaneously improving tillering capacity and panicle branching, thereby leading to higher harvest index and grain yield. Most importantly, pyramiding of the sdt allele and the green revolution gene sd1 enhances grain yield by about 20% in hybrid rice breeding. Our results suggest that the manipulation of the polyadenylation status of OsmiR156 represents a novel strategy for improving the yield potential of rice over what is currently achievable.

Elongation of rice internodes is one of the most important agronomic traits, which determines the plant height and underlies the grain yield. It has been shown that the elongation of internodes is under genetic control, and various factors are implicated in the process. Here, we report a detailed characterization of an elongated uppermost internode1 (eui1) mutant, which has been used in hybrid rice breeding. In the eui1-2 mutant, the cell lengths in the uppermost internodes are significantly longer than that of wild type and thus give rise to the elongated uppermost internode. It was found that the level of active gibberellin was elevated in the mutant, whereas its growth in response to gibberellin is similar to that of the wild type, suggesting that the higher level accumulation of gibberellin in the eui1 mutant causes the abnormal elongation of the uppermost internode. Consistently, the expression levels of several genes which encode gibberellin biosynthesis enzymes were altered. We cloned the EUI1 gene, which encodes a putative cytochrome P450 monooxygenase, by map-based cloning and found that EUI1 was weakly expressed in most tissues, but preferentially in young panicles. To confirm its function, transgenic experiments with different constructs of EUI1 were conducted. Overexpression of EUI1 gave rise to the gibberellin-deficient-like phenotypes, which could be partially reversed by supplementation with gibberellin. Furthermore, apart from the alteration of expression levels of the gibberellin biosynthesis genes, accumulation of SLR1 protein was found in the overexpressing transgenic plants, indicating that the expression level of EUI1 is implicated in both gibberellin-mediated SLR1 destruction and a feedback regulation in gibberellin biosynthesis. Therefore, we proposed that EUI1 plays a negative role in gibberellin-mediated regulation of cell elongation in the uppermost internode of rice.

The deployment of heterosis in the form of hybrid rice varieties has boosted grain yield, but grain quality improvement still remains a challenge. Here we show that a quantitative trait locus for rice grain quality, qGW7, reflects allelic variation of GW7, a gene encoding a TONNEAU1-recruiting motif protein with similarity to C-terminal motifs of the human centrosomal protein CAP350. Upregulation of GW7 expression was correlated with the production of more slender grains, as a result of increased cell division in the longitudinal direction and decreased cell division in the transverse direction. OsSPL16 (GW8), an SBP-domain transcription factor that regulates grain width, bound directly to the GW7 promoter and repressed its expression. The presence of a semidominant GW7(TFA) allele from tropical japonica rice was associated with higher grain quality without the yield penalty imposed by the Basmati gw8 allele. Manipulation of the OsSPL16-GW7 module thus represents a new strategy to simultaneously improve rice yield and grain quality.

The phytohormones ethylene and gibberellin (GA) act synergistically to regulate a diversity of plant growth and development processes. In the presence of ethylene, the signaling mediated by ethylene receptors and CTR1 (CONSTITUTIVE TRIPLE RESPONSE1) is switched off, while EIN2 (ETHYLENE INSENSITIVE2) and EIN3 (ETHYLENE INSENSITIVE3) together mediate ethylene signaling. GA promotes plant growth by facilitating the degradation of the DELLA proteins, a family of nuclear growth repressors. Although the existence of crosstalk between ethylene and GA in the context of growth and development has long been known, its molecular basis is only now beginning to be understood. Both the synthesis and the signaling pathways controlled by ethylene and GA are reciprocally regulated. In this chapter, recent advances in the understanding of how they regulate germination, root and hypocotyl growth, apical hook development, and flowering initiation are reviewed. The significance of ethylene–GA crosstalk in the plant response to abiotic stress is described.

The success of contemporary breeding programmes involving genetic engineering depends on the stability of transgene expression over many generations. We studied the stability of transgene expression in 40 independent rice plant lines representing 11 diverse cultivated varieties. Each line contained three or four different transgenes delivered by particle bombardment, either by cotransformation or in the form of a cointegrate vector. Approximately 75% of the lines (29/40) demonstrated Mendelian inheritance of all transgenes, suggesting integration at a single locus. We found that levels of transgene expression varied among different lines, but primary transformants showing high-level expression of the gna, gusA, hpt and bar transgenes faithfully transmitted these traits to progeny. Furthermore, we found that cry1Ac and cry2A transgene expression was stably inherited when primary transformants showed moderate or low-level expression. Our results show that six transgenes (three markers and three insect-resistance genes) were stably expressed over four generations of transgenic rice plants. We showed that transgene expression was stable in lines of all the rice genotypes we analysed. Our data represent a step forward in the transfer of rice genetic engineering technology from model varieties to elite breeding lines grown in different parts of the world.

Whole plasmids are used in both Agrobacterium-mediated transformation and direct DNA transfer, generally leading to the integration of vector backbone sequences into the host genome along with the transgene(s). This is undesirable, as vector backbone sequences often have negative effects on transgene or endogenous gene expression, and can promote transgene rearrangements. We, therefore, bombarded rice tissue with two constructs: a plasmid containing the bar gene, and a linear DNA fragment isolated from the same plasmid, corresponding to the minimal bar gene expression cassette (promoter, open reading frame and terminator). We recovered phosphinothricin-resistant plants from both experiments, showing that the selectable marker was efficiently expressed. Transformation with such constructs resulted in predominantly 'simple' integration events (one or two bands on Southern blots), producing low-copy-number transgenic plants with a low frequency of transgene rearrangements. Conversely, transformation with supercoiled or linearized whole plasmids generated plants with 'complex' integration patterns, that is, higher copy numbers and frequent transgene rearrangements. We monitored transgenic lines through to the R4 generation and observed no silencing in plants carrying minimal constructs. We also carried out experiments in which rice tissue was simultaneously bombarded with minimal linear hpt and gusA cassettes. We observed robust GUS activity in hygromycin-resistant plants, confirming co-expression of the selectable and nonselectable markers. Furthermore, the efficiency of cotransformation using minimal constructs was the same as that using supercoiled plasmid cointegrate vectors.

Transgenic rice (Oryza sativa L.) plants generated through particle bombardment expressed high levels of an insecticidal protein (the snowdrop lectin, GNA) directed against sap-sucking insects. Engineered plants expressed GNA either constitutively or in a tissue specific manner, depending on the nature of the promoter used to drive expression of the gene. We used specific antibodies raised against GNA to localize its expression in phloem tissue in plants engineered with the rice sucrose synthase promoter driving GNA expression. We report here molecular, biochemical and immunological analyses for fifteen independently-derived transformants out of more than 200 plants we generated.

Phosphatidylserine (PS), a quantitatively minor membrane phospholipid, is involved in many biological processes besides its role in membrane structure. One PS synthesis gene, PHOSPHATIDYLSERINE SYNTHASE1 (PSS1), has been discovered to be required for microspore development in Arabidopsis thaliana L. but how PSS1 affects postembryonic development is still largely unknown. Here, we show that PSS1 is also required for inflorescence meristem and organ development in Arabidopsis. Disruption of PSS1 causes severe dwarfism, smaller lateral organs and reduced size of inflorescence meristem. Morphological and molecular studies suggest that both cell division and cell elongation are affected in the pss1-1 mutant. RNA in situ hybridization and promoter GUS analysis show that expression of both WUSCHEL (WUS) and CLAVATA3 (CLV3) depend on PSS1. Moreover, the defect in meristem maintenance is recovered and the expression of WUS and CLV3 are restored in the pss1-1 clv1-1 double mutant. Both SHOOTSTEMLESS (STM) and BREVIPEDICELLUS (BP) are upregulated, and auxin distribution is disrupted in rosette leaves of pss1-1. However, expression of BP, which is also a regulator of internode development, is lost in the pss1-1 inflorescence stem. Our data suggest that PSS1 plays essential roles in inflorescence meristem maintenance through the WUS-CLV pathway, and in leaf and internode development by differentially regulating the class I KNOX genes.

• Control of organ size and shape by cell proliferation and cell expansion is a fundamental developmental process, but the mechanisms that set the size and shape of determinate organs are largely unknown in plants. • Molecular, genetic, cytological and biochemical approaches were used to characterize the roles of the Arabidopsis thaliana G protein γ subunit (AGG3) gene in organ growth. • Here, we describe A. thaliana AGG3, which promotes petal growth by increasing the period of cell proliferation. Both the N-terminal region and the C-terminal domains of AGG3 are necessary for the function of AGG3. By contrast, analysis of a series of AGG3 derivatives with deletions in specific domains showed that the deletion of any of these domains cannot completely abolish the function of AGG3. The GFP-AGG3 fusion protein is localized to the plasma membrane. The predicted transmembrane domain plays an important role in the plasma membrane localization of AGG3. Genetic analyses revealed that AGG3 action requires a functional G protein α subunit (GPA1) and G protein β subunit (AGB1). • Our findings demonstrate that AGG3, GPA1 and AGB1 act in the same genetic pathway to influence organ size and shape in A. thaliana.

Grain size and shape are important components of grain yield and quality and have been under selection since cereals were first domesticated. Here, we show that a quantitative trait locus GW8 is synonymous with OsSPL16, which encodes a protein that is a positive regulator of cell proliferation. Higher expression of this gene promotes cell division and grain filling, with positive consequences for grain width and yield in rice. Conversely, a loss-of-function mutation in Basmati rice is associated with the formation of a more slender grain and better quality of appearance. The correlation between grain size and allelic variation at the GW8 locus suggests that mutations within the promoter region were likely selected in rice breeding programs. We also show that a marker-assisted strategy targeted at elite alleles of GS3 and OsSPL16 underlying grain size and shape can be effectively used to simultaneously improve grain quality and yield.

Facing the current increasingly serious network security situation, one model of networked system security situation evaluation and definition of attack factors was presented based on the problems. Then, attack frequency, attack difficult degree and attack compromise degree were quantized in dynamic method. It made to indicate the success number, probability of success and the extent of harm more precisely. In view of the uncertainty, un-integrity fuzzy and changeability of the attack information, this thesis put forward a method of fuzzy information fusion which was based on Mamdani fuzzy reasoning method to realize the association of attack factors. Then, this thesis used Matlab 7.0 simulating tool to conduct the experiment. The experiment showed that the method raised in this thesis really reflected the security situation format.

The phytohormone gibberellic acid (GA) regulates diverse aspects of plant growth and development. GA responses are triggered by the degradation of DELLA proteins, which function as repressors in GA signaling pathways. Recent studies in Arabidopsis thaliana and rice (Oryza sativa) have implied that the degradation of DELLA proteins occurred via the ubiquitin-proteasome system. Here, we developed an Arabidopsis cell-free system to recapitulate DELLA protein degradation in vitro. Using this cell-free system, we documented that Lys-29 of ubiquitin is the major site for ubiquitin chain formation to mediate DELLA protein degradation. We also confirmed the specific roles of GA receptors and multisubunit E3 ligase components in regulating DELLA protein degradation. In addition, blocking DELLA degradation with a PP1/PP2A phosphatase inhibitor in our cell-free assay suggested that degradation of DELLA proteins required protein Ser/Thr dephosphorylation activity. Furthermore, our data revealed that the LZ domain of Arabidopsis DELLA proteins is essential for both their stability and activity. Thus, our in vitro degradation system provides biochemical insights into the regulation of DELLA protein degradation. This in vitro assay system could be widely adapted for dissecting cellular signaling pathways in which regulated proteolysis is a key recurrent theme.

Light and gibberellins (GAs) mediate many essential and partially overlapping plant developmental processes. DELLA proteins are GA-signalling repressors that block GA-induced development1. GA induces degradation of DELLA proteins via the ubiquitin/proteasome pathway2, but light promotes accumulation of DELLA proteins by reducing GA levels3. It was proposed that DELLA proteins restrain plant growth largely through their effect on gene expression4,5. However, the precise mechanism of their function in coordinating GA signalling and gene expression remains unknown. Here we characterize a nuclear protein interaction cascade mediating transduction of GA signals to the activity regulation of a light-responsive transcription factor. In the absence of GA, nuclear-localized DELLA proteins accumulate to higher levels, interact with phytochrome-interacting factor 3 (PIF3, a bHLH-type transcription factor) and prevent PIF3 from binding to its target gene promoters and regulating gene expression, and therefore abrogate PIF3-mediated light control of hypocotyl elongation. In the presence of GA, GID1 proteins (GA receptors) elevate their direct interaction with DELLA proteins in the nucleus, trigger DELLA protein’s ubiquitination and proteasome-mediated degradation, and thus release PIF3 from the negative effect of DELLA proteins.

Plant morphogenesis is profoundly influenced by light (a phenomenon known as photomorphogenesis). For example, light inhibits seedling hypocotyl growth via activation of phytochromes and additional photoreceptors. Subsequently, information is transmitted through photoreceptor-linked signal transduction pathways and used (via previously unknown mechanisms) to control hypocotyl growth. Here we show that light inhibition of Arabidopsis (Arabidopsis thaliana) hypocotyl growth is in part dependent on the DELLAs (a family of nuclear growth-restraining proteins that mediate the effect of the phytohormone gibberellin [GA] on growth). We show that light inhibition of growth is reduced in DELLA-deficient mutant hypocotyls. We also show that light activation of phytochromes promotes the accumulation of DELLAs. A green fluorescent protein (GFP)-tagged DELLA (GFP-RGA) accumulates in elongating cells of light-grown, but not dark-grown, transgenic wild-type hypocotyls. Furthermore, transfer of seedlings from light to dark (or vice versa) results in rapid changes in hypocotyl GFP-RGA accumulation, changes that are paralleled by rapid alterations in the abundance in hypocotyls of transcripts encoding enzymes of GA metabolism. These observations suggest that light-dependent changes in hypocotyl GFP-RGA accumulation are a consequence of light-dependent changes in bioactive GA level. Finally, we show that GFP accumulation and quantitative modulation of hypocotyl growth is proportionate with light energy dose (the product of exposure duration and fluence rate). Hence, DELLAs inhibit hypocotyl growth during the light phase of the day-night cycle via a mechanism that is quantitatively responsive to natural light variability. We conclude that DELLAs are a major component of the adaptively significant mechanism via which light regulates plant growth during photomorphogenesis.

This article describes a personal video recorder (PVR) system that uses H.264 for video coding and MPEG-2 transport stream as data format for simultaneous record and playback. Using H.264 provides two times longer recording time over MPEG-2 based on the same video quality. The 2004 amendment of the MPEG-2 system standard added support for the transport of none MPEG-2 AVC video data using MPEG-2 transport stream. This article discusses the overall architecture of the PVR and several key technical aspects of the implementation, including A/V capture, synchronization, storage and play-back. The implementation uses the Davinci digital video software development kit (DVSDK).

The plant cell wall-associated kinase (WAK) and WAK-like kinase (WAKL) make up a unique group in the receptor-like protein kinase (RLK) superfamily. Previous studies on Arabidopsis have revealed that the WAK gene family members play an important role in both cell elongation and stress response signalling. Here we show that four putative WAKs (TaWAK1, TaWAKL2, TaWAKL3, and TaWAK4) and two WAKLs (TaWAKL1 and TaWAKL2) were isolated from wheat based on the DNA sequence similarity and the protein structure conservation of Arabidopsis WAKs genes. TaWAK1, TaWAK2, TaWAK3 and TaWAKL1 each encode a putative intact protein with the characteristic of the WAK / WAKL gene family members, except for the abbreviated TaWAK4 and TaWAKL2 which were caused by nucleotide mutation and alternative splicing, respectively. Southern analysis revealed that TaWAKL1, TaWAK1, TaWAK2 and TaWAK3 are all multiple-copy members. Real-time PCR analysis revealed that the TaWAK1 and TaWAK3 displayed similar expression patterns, while expressions of TaWAKL1, TaWAKL2, and TaWAK2 were organ specific. Further, we analysed the conservation of introns and intron–exon structure and the putative protein structures between wheat and Arabidopsis, which showed the putative wheat WAKs are different from those of Arabidopsis and make up a new subgroup in the polygenetic tree.

The phytohormone gibberellin (GA) regulates the development and fertility of Arabidopsis flowers. The mature flowers of GA-deficient mutant plants typically exhibit reduced elongation growth of petals and stamens. In addition, GA-deficiency blocks anther development, resulting in male sterility. Previous analyses have shown that GA promotes the elongation of plant organs by opposing the function of the DELLA proteins, a family of nuclear growth repressors. However, it was not clear that the DELLA proteins are involved in the GA-regulation of stamen and anther development. We show that GA regulates cell elongation rather than cell division during Arabidopsis stamen filament elongation. In addition, GA regulates the cellular developmental pathway of anthers leading from microspore to mature pollen grain. Genetic analysis shows that the Arabidopsis DELLA proteins RGA and RGL2 jointly repress petal, stamen and anther development in GA-deficient plants, and that this function is enhanced by RGL1 activity. GA thus promotes Arabidopsis petal, stamen and anther development by opposing the function of the DELLA proteins RGA, RGL1 and RGL2.

The growth of plant organs is influenced by a stream of the phytohormone auxin that flows from the shoot apex to the tip of the root 1 . However, until now it has not been known how auxin regulates the cell proliferation and enlargement that characterizes organ growth. Here we show that auxin controls the growth of roots by modulating cellular responses to the phytohormone gibberellin (GA). GA promotes the growth of plants by opposing the effects of nuclear DELLA protein growth repressors 2‐8 , one of which is Arabidopsis RGA (for repressor of gal-3) 9,10 . GA opposes the action of several DELLA proteins by destabilizing them, reducing both the concentration of detectable DELLA proteins and their growth-restraining effects 9‐14 . We also show that auxin is necessary for GA-mediated control of root growth, and that attenuation of auxin transport or signalling delays the GA-induced disappearance of RGA from root cell nuclei. Our observations indicate that the shoot apex exerts long-distance control on the growth of plant organs through the effect of auxin on GA-mediated DELLA protein destabilization. Auxin mediates at least some of its effects on plant growth by inducing the proteasome-mediated degradation of AUX/IAA proteins 15,16 . However, the mechanism by which auxin regulates growth remains unclear. Furthermore, it is not known how the auxin and GA signalling pathways interact with one another 17 . Here we demonstrate a molecular link between auxin-mediated and GA-mediated growth regulation: auxin controls the growth of Arabidopsis roots through the modulation of the cellular response to GA. Although GA has long been known to regulate shoot growth, its role in the regulation of root growth was less clear. We showed that primary roots of the GA-deficient Arabidopsis ga1-3 mutant 5 are shorter than those of the wild type, whereas GA-treated ga1-3 roots are of a similar length to those of the wild type (Fig. 1a). Thus, GA regulates root growth. Arabidopsis contains genes encoding five DELLA proteins (GAI, RGA, RGL1, RGL2 and RGL3), and genetic analysis has shown that some of these proteins mediate specific components of the GA response 2,3,5‐8 . We showed that roots lacking GAI (gai-t6 ga1-3) or RGA (rga-24 ga1-3) are longer than ga1-3 controls (Fig. 1b), whereas a lack of both GAI and RGA (gai-t6 rga-24 ga1-3) substantially suppresses the ga1-3 phenotype (Fig. 1b). Thus, GAI and RGA act together in the regulation of root (and shoot 5,6 ) growth, as growth repressors whose function is opposed by

DELLA proteins are nuclear repressors of plant gibberellin (GA) responses. Here, we investigate the properties of SLN1, a DELLA protein from barley that is destabilized by GA treatment. Using specific inhibitors of proteasome function, we show that proteasome-mediated protein degradation is necessary for GA-mediated destabilization of SLN1. We also show that GA responses, such as the aleurone alpha-amylase response and seedling leaf extension growth, require proteasome-dependent GA-mediated SLN1 destabilization. In further experiments with protein kinase and protein phosphatase inhibitors, we identify two additional signaling steps that are necessary for GA response and for GA-mediated destabilization of SLN1. Thus, GA signaling involves protein phosphorylation and dephosphorylation steps and promotes the derepression of GA responses via proteasome-dependent destabilization of DELLA repressors.

We investigated transgene silencing in a line of rice plants that carries a single-copy 6.6-kb transgenic locus comprising three heterologous transgenes: bar, hpt and gusA. We identified at least three distinct types of silencing effects associated with different methylation patterns, including a novel form of transcriptional silencing involving methylation of cytosine residues only at non-conventional acceptor sites in the coding region. Silencing arose de novo in individual R1, R2 and R3 plants despite the stability of the transgenic locus, although the basic structure of the locus, transgene dosage and position effects remained constant within the line. We found that different silencing effects could occur concurrently in adjacent heterologous transgenes in the same plant, with no evidence for spreading of silenced states or methylation patterns from one transgene to another.

Snowdrop lectin (Galanthus nivalis agglutinin; GNA) has been shown previously to be toxic towards rice brown planthopper (Nilaparvata lugens; BPH) when administered in artificial diet. BPH feeds by phloem abstraction, and causes 'hopper burn', as well as being an important virus vector. To evaluate the potential of the gna gene to confer resistance towards BPH, transgenic rice (Oryza sativa L.) plants were produced, containing the gna gene in constructs where its expression was driven by a phloem-specific promoter (from the rice sucrose synthase RSs1 gene) and by a constitutive promoter (from the maize ubiquitin ubi1 gene). PCR and Southern analyses on DNA from these plants confirmed their transgenic status, and that the transgenes were transmitted to progeny after self-fertilization. Western blot analyses revealed expression of GNA at levels of up to 2.0% of total protein in some of the transgenic plants. GNA expression driven by the RSs1 promoter was tissue-specific, as shown by immunohistochemical localization of the protein in the non-lignified vascular tissue of transgenic plants. Insect bioassays and feeding studies showed that GNA expressed in the transgenic rice plants decreased survival and overall fecundity (production of offspring) of the insects, retarded insect development, and had a deterrent effect on BPH feeding. gna is the first transgene to exhibit insecticidal activity towards sap-sucking insects in an important cereal crop plant.

Bioactive gibberellins (GAs) are essential endogenous regulators of plant growth. GA signaling is mediated via GAI, a nuclear member of the GRAS family of plant transcription factors. Previous experiments have suggested that GAI is a GA-derepressible repressor of plant growth. Here we test this hypothesis by examining the effects of the expression of Arabidopsis GAI in transgenic Basmati rice. High-level expression of GAI caused dwarfism and reduced GA responses, and the strength of this effect was correlated with the level of transgene expression. In particular, the expression of GAI abolished the GA-mediated induction of rice aleurone alpha-amylase activity, thus implicating GAI orthologs in the well-characterized cereal aleurone GA response. The GA derepressible repressor model predicts that high-level expression of GAI should confer dwarfism, and these observations are consistent with this prediction.