Overexpression of an ABA biosynthesis gene using a stress-inducible promoter enhances drought resistance in petunia

The response of plants to drought stress includes reduced transpiration as stomates close in response to increased abscisic acid(ABA)concentrations.Constitutive overexpression of 9-cis-epoxycarotenoid dioxygenase(NCED),a key enzyme in ABA biosynthesis,increases drought resistance,but causes negative pleiotropic effects on plant growth and development.We overexpressed the tomato NCED(LeNCED1)in petunia plants under the control of a stress-inducible promoter,rd29A.Under water stress,the transgenic plants had increased transcripts of NCED mRNA,elevated leaf ABA concentrations,increased concentrations of proline,and a significant increase in drought resistance.The transgenic plants also displayed the expected decreases in stomatal conductance,transpiration,and photosynthesis.After 14 days without water,the control plants were dead,but the transgenic plants,though wilted,recovered fully when re-watered.Well-watered transgenic plants grew like non-transformed control plants and there was no effect of the transgene on seed dormancy.

A basic helix-loop-helix transcription factor, PhFBH4, regulates flower senescence by modulating ethylene biosynthesis pathway in petunia

The basic helix-loop-helix(bHLH)transcription factors(TFs)play important roles in regulating multiple biological processes in plants.However,there are few reports about the function of bHLHs in flower senescence.In this study,a bHLH TF,PhFBH4,was found to be dramatically upregulated during flower senescence.Transcription of PhFBH4 is induced by plant hormones and abiotic stress treatments.Silencing of PhFBH4 using virus-induced gene silencing or an antisense approach extended flower longevity,while transgenic petunia flowers with an overexpression construct showed a reduction in flower lifespan.Abundance of transcripts of senescence-related genes(SAG12,SAG29)was significantly changed in petunia PhFBH4 transgenic flowers.Furthermore,silencing or overexpression of PhFBH4 reduced or increased,respectively,transcript abundances of important ethylene biosynthesis-related genes,ACS1 and ACO1,thereby influencing ethylene production.An electrophoretic mobility shift assay showed that the PhFBH4 protein physically interacted with the G-box cis-element in the promoter of ACS1,suggesting that ACS1 was a direct target of the PhFBH4 protein.In addition,ectopic expression of this gene altered plant development including plant height,internode length,and size of leaves and flowers,accompanied by alteration of transcript abundance of the gibberellin biosynthesis-related gene GA2OX3.Our results indicate that PhFBH4 plays an important role in regulating plant growth and development through modulating the ethylene biosynthesis pathway.

Controlling plant architecture by manipulation of gibberellicacid signalling in petunia

Since stem elongation is a gibberellic acid(GA)response,GA inhibitors are commonly used to control plant height in the production of potted ornamentals and bedding plants.In this study,we investigated interfering with GA signaling by using molecular techniques as an alternative approach.We isolated three putative GID1 genes(PhGID1A,PhGID1B and PhGID1C)encoding GA receptors from petunia.Virus-induced gene silencing(VIGS)of these genes results in stunted growth,dark-green leaves and late-flowering.We also isolated the gai mutant gene(gai-1)from Arabidopsis.We have generated transgenic petunia plants in which the gai mutant protein is over-expressed under the control of a dexamethasone-inducible promoter.This system permits induction of the dominant Arabidopsis gai mutant gene at a desired stage of plant development in petunia plants by the application of dexamethasone(Dex).The induction of gai in Dex-treated T1 petunia seedlings caused dramatic growth retardation with short internodes.

Transcriptomic analysis reveals numerous diverse protein kinases and transcription factors involved in desiccation tolerance in the resurrection plant Myrothamnus flabellifolia

The woody resurrection plant Myrothamnus flabellifolia has remarkable tolerance to desiccation.Pyro-sequencing technology permitted us to analyze the transcriptome of M.flabellifolia during both dehydration and rehydration.We identified a total of 8287 and 8542 differentially transcribed genes during dehydration and rehydration treatments respectively.Approximately 295 transcription factors(TFs)and 484 protein kinases(PKs)were up-or down-regulated in response to desiccation stress.Among these,the transcript levels of 53 TFs and 91 PKs increased rapidly and peaked early during dehydration.These regulators transduce signal cascades of molecular pathways,including the up-regulation of ABA-dependent and independent drought stress pathways and the activation of protective mechanisms for coping with oxidative damage.Antioxidant systems are up-regulated,and the photosynthetic system is modified to reduce ROS generation.Secondary metabolism may participate in the desiccation tolerance of M.flabellifolia as indicated by increases in transcript abundance of genes involved in isopentenyl diphosphate biosynthesis.Up-regulation of genes encoding late embryogenesis abundant proteins and sucrose phosphate synthase is also associated with increased tolerance to desiccation.During rehydration,the transcriptome is also enriched in transcripts of genes encoding TFs and PKs,as well as genes involved in photosynthesis,and protein synthesis.The data reported here contribute comprehensive insights into the molecular mechanisms of desiccation tolerance in M.flabellifolia.