Over-expression of a Type-A Response Regulator Alters Rice Morphology and Cytokinin Metabolism
Ontology highlight
ABSTRACT:
ORGANISM(S): Oryza sativa
PROVIDER: GSE6737 | GEO | 2007/02/15
SECONDARY ACCESSION(S): PRJNA98971
REPOSITORIES: GEO
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Project description:Cytokinin plays crucial roles in regulating plant growth and development, with the signal transduction mediated by type-A and type-B response regulators (RRs).While much genetic knowledge about RRs on regulating plant height remains unclear. Here, we found that overexpressing an OsORR2 gene (a type-B RR) could reduce plant height in rice compared with the wild type (WT). Using quantitative real time (RT-qPCR) assay, OsORR2was expressed widely in most tissues such as root, culm, sheath, leaf, and panicle. Strong signals were detected in leaf mesophyll cells and anther by in situ hybridization assays (ISH). The subcellular localization of OsORR2 was in cell nucleus. In addition, we found that the transcriptional expression levels of type-A RR genes such as OsRR9, OsRR10, OsRR12, and OsRR13 were significantly up-regulated in the overexpression transgenic plants (OE) plants. Taken together, our data suggested that OsORR2was involved in the development of plant height in rice and provided a foundation for future deep molecular research of the type-B RRs.
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Project description:The expression patterns of the NRT2 genes have been well described; however, the role of OsNRT2.4 in root growth is not well known. In this study, we thus aimed at investigating the role of high-affinity NO3− transport OsNRT2.4 in root growth modulation. Through the amiRNA-mediated gene silencing technique, we successfully obtained osnrt2.4 knockdown lines to study the role of OsNRT2.4 on root growth under low nitrate conditions. We performed real-time PCR analysis to investigate the relative gene expression level in root and shoot, soluble metabolites, and measurement of root system. Knockdown of OsNRT2.4 decreased rice growth. The comparison with wild-type (WT) plants showed that (i) knockdown of OsNRT2.4 inhibited root formation under low NO3− supply; (ii) we demonstrated that the mutant lines had significantly increased NO3− uptake than WT plants when grown in different nitrate supplies; (iii) osnrt2.4 knockdown lines showed an alteration in nitrogen metabolism, and this affected the root growth; and (iv) the downregulation of OsNRT2.4 enhanced the expression of gene response of low external NO3− concentrations. Herein we provide new insights in OsNRT2.4 functions. Our data demonstrated that OsNRT2.4 plays a role in root growth, nitrogen metabolic pathway and probably have functions in nitrate transport from root to shoot under low nitrate availability in rice. Supplementary Information The online version contains supplementary material available at 10.1007/s11032-021-01273-6.
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Project description:The phytohormone cytokinin plays a critical role in regulating growth and development throughout the life cycle of the plant. The primary transcriptional response to cytokinin is mediated by the action of the type-B response regulators (RRs), with much of our understanding for their functional roles being derived from studies in the dicot Arabidopsis. To examine the roles played by type-B RRs in a monocot, we employed gain-of-function and loss-of-function mutations to characterize RR22 function in rice. Ectopic overexpression of RR22 in rice results in an enhanced cytokinin response based on molecular and physiological assays. Phenotypes associated with enhanced activity of RR22 include effects on leaf and root growth, inflorescence architecture, and trichome formation. Analysis of four Tos17 insertion alleles of RR22 revealed effects on inflorescence architecture, trichomes, and development of the stigma brush involved in pollen capture. Both loss- and gain-of-function RR22 alleles affected the number of leaf silica-cell files, which provide mechanical stability and improve resistance to pathogens. Taken together, these results indicate that a delicate balance of cytokinin transcriptional activity is necessary for optimal growth and development in rice.
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Project description:In vitro, a new protocol of plant regeneration in rose was achieved via protocorm-like bodies (PLBs) induced from the root-like organs named rhizoids that developed from leaf explants. The development of rhizoids is a critical stage for efficient regeneration, which is triggered by exogenous auxin. However, the role of cytokinin in the control of organogenesis in rose is as yet uncharacterized. The aim of this study was to elucidate the molecular mechanism of cytokinin-modulated rhizoid formation in Rosa canina. Here, we found that cytokinin is a key regulator in the formation of rhizoids. Treatment with cytokinin reduced callus activity and significantly inhibited rhizoid formation in Rosa canina. We further isolated the full-length cDNA of a type-A response regulator gene of cytokinin signaling, RcRR1, from which the deduced amino acid sequence contained the conserved DDK motif. Gene expression analysis revealed that RcRR1 was differentially expressed during rhizoid formation and its expression level was rapidly up-regulated by cytokinin. In addition, the functionality of RcRR1 was tested in Arabidopsis. RcRR1 was found to be localized to the nucleus in GFP-RcRR1 transgenic plants and overexpression of RcRR1 resulted in increased primary root length and lateral root density. More importantly, RcRR1 overexpression transgenic plants also showed reduced sensitivity to cytokinin during root growth; auxin distribution and the expression of auxin efflux carriers PIN genes were altered in RcRR1 overexpression plants. Taken together, these results demonstrate that RcRR1 is a functional type-A response regulator which is involved in cytokinin-regulated rhizoid formation in Rosa canina.
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Project description:BackgroundThe number of grains per panicle is an important factor in determining rice yield. The DST-OsCKX2 module has been demonstrated to regulate panicle development in rice by controlling cytokinin content. However, to date, how the function of DST-OsCKX2 module is regulated during panicle development remains obscure.ResultIn this study, the ABNORMAL PANICLE 1 (ABP1), a severely allele of FRIZZY PANICLE (FZP), exhibits abnormal spikelets morphology. We show that FZP can repress the expression of DST via directly binding to its promotor. Consistently, the expression level of OsCKX2 increased and the cytokinin content decreased in the fzp mutant, suggesting that the FZP acts upstream of the DST-OsCKX2 to maintain cytokinin homeostasis in the inflorescence meristem.ConclusionsOur results indicate that FZP plays an important role in regulating spikelet development and grain number through mediating cytokinin metabolism.
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Project description:BackgroundThe response regulators represent the elements of bacterial two-component system and have been characterized from dicot plants like Arabidopsis but little information is available on the monocots, including the cereal crops. The aim of this study was to characterize type-A response regulator genes from rice, and to investigate their expression in various organs as well as in response to different hormones, including cytokinin, and environmental stimuli.ResultsBy analysis of the whole genome sequence of rice, we have identified ten genes encoding type-A response regulators based upon their high sequence identity within the receiver domain. The exon-intron organization, intron-phasing as well as chromosomal location of all the RT-PCR amplified rice (Oryza sativa) response regulator (OsRR) genes have been analyzed. The transcripts of OsRR genes could be detected by real-time PCR in all organs of the light- and dark-grown rice seedlings/plants, although there were quantitative differences. The steady-state transcript levels of most of the OsRR genes increased rapidly (within 15 min) on exogenous cytokinin application even in the presence of cycloheximide. Moreover, the expression of the OsRR6 gene was enhanced in rice seedlings exposed to salinity, dehydration and low temperature stress.ConclusionTen type-A response regulator genes identified in rice, the model monocot plant, show overlapping/differential expression patterns in various organs and in response to light. The induction of OsRR genes by cytokinin even in the absence of de novo protein synthesis qualifies them to be primary cytokinin response genes. The induction of OsRR6 in response to different environmental stimuli indicates its role in cross-talk between abiotic stress and cytokinin signaling. These results provide a foundation for further investigations on specific as well as overlapping cellular functions of type-A response regulators in rice.
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Project description:The plant hormone cytokinin affects a diverse array of growth and development processes and responses to the environment. How a signaling molecule mediates such a diverse array of outputs and how these response pathways are integrated with other inputs remain fundamental questions in plant biology. To this end, we characterized the transcriptional network initiated by the type-B ARABIDOPSIS RESPONSE REGULATORs (ARRs) that mediate the cytokinin primary response, making use of chromatin immunoprecipitation sequencing (ChIP-seq), protein-binding microarrays, and transcriptomic approaches. By ectopic overexpression of ARR10, Arabidopsis lines hypersensitive to cytokinin were generated and used to clarify the role of cytokinin in regulation of various physiological responses. ChIP-seq was used to identify the cytokinin-dependent targets for ARR10, thereby defining a crucial link between the cytokinin primary-response pathway and the transcriptional changes that mediate physiological responses to this phytohormone. Binding of ARR10 was induced by cytokinin with binding sites enriched toward the transcriptional start sites for both induced and repressed genes. Three type-B ARR DNA-binding motifs, determined by use of protein-binding microarrays, were enriched at ARR10 binding sites, confirming their physiological relevance. WUSCHEL was identified as a direct target of ARR10, with its cytokinin-enhanced expression resulting in enhanced shooting in tissue culture. Results from our analyses shed light on the physiological role of the type-B ARRs in regulating the cytokinin response, mechanism of type-B ARR activation, and basis by which cytokinin regulates diverse aspects of growth and development as well as responses to biotic and abiotic factors.
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Project description:Maize originated as a tropical plant that required short days to transition from vegetative to reproductive development. ZmCCT10 [CO, CONSTANS, CO-LIKE and TIMING OF CAB1 (CCT) transcription factor family] is a regulator of photoperiod response and was identified as a major QTL controlling photoperiod sensitivity in maize. We modulated expression of ZmCCT10 in transgenic maize using two constitutive promoters with different expression levels. Transgenic plants over expressing ZmCCT10 with either promoter were delayed in their transition from vegetative to reproductive development but were not affected in their switch from juvenile-to-adult vegetative growth. Strikingly, transgenic plants containing the stronger expressing construct had a prolonged period of vegetative growth accompanied with dramatic modifications to plant architecture that impacted both vegetative and reproductive traits. These plants did not produce ears, but tassels were heavily branched. In more than half of the transgenic plants, tassels were converted into a branched leafy structure resembling phyllody, often composed of vegetative plantlets. Analysis of expression modules controlling the floral transition and meristem identity linked these networks to photoperiod dependent regulation, whereas phase change modules appeared to be photoperiod independent. Results from this study clarified the influence of the photoperiod pathway on vegetative and reproductive development and allowed for the fine-tuning of the maize flowering time model.
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Project description:Adventitious root formation at the base of plant cuttings is an innate de novo organogenesis process that allows massive vegetative propagation of many economically and ecologically important species. The early molecular events following shoot excision are not well understood. Using whole-genome microarrays, we detected significant transcriptome remodeling during 48 hours following shoot removal in Populus softwood cuttings in the absence of exogenous auxin, with 27% and 36% of the gene models showing differential abundance between 0 and 6 hours, and 6 and 24 hours, respectively. During these two time intervals, gene networks involved in protein turnover, protein phosphorylation, molecular transport and translation were among the most significantly regulated. Transgenic lines expressing a constitutively active form of the Populus type-B response regulator PtRR13 (ΔDDKPtRR13) have a delayed rooting phenotype and cause misregulation of COV1, a negative regulator of vascularization; PDR9, an auxin efflux transporter; two AP2/ERF genes with sequence similarity to TINY1. Cytokinin action appeared to disrupt root development 24 hours after shoot excision, when root founder cells are hypothesized to be sensitive to the negative effects of cytokinin. Our results suggest that PtRR13 acts downstream of cytokinin to repress adventitious root formation in intact plants, and that reduced cytokinin signaling after shoot excision enables coordinated expression of ethylene, auxin and vascularization pathways leading to adventitious root development.
2009-03-27 | GSE15049 | GEO
Project description:Inflorescence development in cereals, including such important crops as rice, maize, and wheat, directly affects grain number and size and is a key determinant of yield. Cytokinin regulates meristem size and activity and, as a result, has profound effects on inflorescence development and architecture. To clarify the role of cytokinin action in inflorescence development, we used the NanoString nCounter system to analyze gene expression in the early stages of rice panicle development, focusing on 67 genes involved in cytokinin biosynthesis, degradation, and signaling. Results point toward key members of these gene families involved in panicle development and indicate that the expression of many genes involved in cytokinin action differs between the panicle and vegetative tissues. Dynamic patterns of gene expression suggest that subnetworks mediate cytokinin action during different stages of panicle development. The variation of expression during panicle development is greater among genes encoding proteins involved in cytokinin metabolism and negative regulators of the pathway than for the genes in the primary response pathway. These results provide insight into the expression patterns of genes involved in cytokinin action during inflorescence development in a crop of agricultural importance, with relevance to similar processes in other monocots. The identification of subnetworks of genes expressed at different stages of early panicle development suggests that manipulation of their expression could have substantial effects on inflorescence architecture.
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