Strigolactones modulate cotton fiber elongation and secondary cell wall thickening

Cotton is one of the most important economic crops in the world,and it is a major source of fiber in the textile industry.Strigolactones(SLs)are a class of carotenoid-derived plant hormones involved in many processes of plant growth and development,although the functions of SL in fiber development remain largely unknown.Here,we found that the endogenous SLs were significantly higher in fibers at 20 days post-anthesis(DPA).Exogenous SLs significantly increased fiber length and cell wall thickness.Furthermore,we cloned three key SL biosynthetic genes,namely GhD27,GhMAX3,and GhMAX4,which were highly expressed in fibers,and subcellular localization analyses revealed that GhD27,GhMAX3,and GhMAX4 were localized in the chloroplast.The exogenous expression of GhD27,GhMAX3,and GhMAX4 complemented the physiological phenotypes of d27,max3,and max4 mutations in Arabidopsis,respectively.Knockdown of GhD27,GhMAX3,and GhMAX4 in cotton resulted in increased numbers of axillary buds and leaves,reduced fiber length,and significantly reduced fiber thickness.These findings revealed that SLs participate in plant growth,fiber elongation,and secondary cell wall formation in cotton.These results provide new and effective genetic resources for improving cotton fiber yield and plant architecture.

Chemokine platelet factor 4 accelerates peripheral nerve regeneration by regulating Schwann cell activation and axon elongation

Schwann cells in peripheral nerves react to traumatic nerve injury by attempting to grow and regenerate.Howeve r,it is unclear what factors play a role in this process.In this study,we searched a GEO database and found that expression of platelet factor 4 was markedly up-regulated after sciatic nerve injury.Platelet factor is an important molecule in cell apoptosis,diffe rentiation,survival,and proliferation.Further,polymerase chain reaction and immunohistochemical staining confirmed the change in platelet factor 4 in the sciatic nerve at different time points after injury.Enzyme-linked immunosorbent assay confirmed that platelet factor 4 was secreted by Schwann cells.We also found that silencing platelet factor 4 decreased the proliferation and migration of primary cultured Schwann cells,while exogenously applied platelet factor 4 stimulated Schwann cell prolife ration and migration and neuronal axon growth.Furthermore,knocking out platelet factor 4 inhibited the prolife ration of Schwann cells in injured rat sciatic nerve.These findings suggest that Schwann cell-secreted platelet factor 4 may facilitate peripheral nerve repair and regeneration by regulating Schwann cell activation and axon growth.Thus,platelet factor 4 may be a potential therapeutic target for traumatic peripheral nerve injury.

Chain Elongation Using Native Soil Inocula:Exceptional n-Caproate Biosynthesis Performance and Microbial Mechanisms

This study demonstrates the feasibility and effectiveness of utilizing native soils as a resource for inocula to produce n-caproate through the chain elongation(CE)platform,offering new insights into anaerobic soil processes.The results reveal that all five of the tested soil types exhibit CE activity when supplied with high concentrations of ethanol and acetate,highlighting the suitability of soil as an ideal source for n-caproate production.Compared with anaerobic sludge and pit mud,the native soil CE system exhibited higher selectivity(60.53%),specificity(82.32%),carbon distribution(60.00%),electron transfer efficiency(165.00%),and conductivity(0.59 ms∙cm^(-1)).Kinetic analysis further confirmed the superiority of soil in terms of a shorter lag time and higher yield.A microbial community analysis indicated a positive correlation between the relative abundances of Pseudomonas,Azotobacter,and Clostridium and n-caproate production.Moreover,metagenomics analysis revealed a higher abundance of functional genes in key microbial species,providing direct insights into the pathways involved in n-caproate formation,including in situ CO_(2)utilization,ethanol oxidation,fatty acid biosynthesis(FAB),and reverse beta-oxidation(RBO).The numerous functions in FAB and RBO are primarily associated with Pseudomonas,Clostridium,Rhodococcus,Stenotrophomonas,and Geobacter,suggesting that these genera may play roles that are involved or associated with the CE process.Overall,this innovative inoculation strategy offers an efficient microbial source for n-caproate production,underscoring the importance of considering CE activity in anaerobic soil microbial ecology and holding potential for significant economic and environmental benefits through soil consortia exploration.

Vital contribution of brassinosteroids to hypoxia-stimulated coleoptile elongation in submerged rice

The rapid elongation of rice(Oryza sativa)coleoptile is pivotal for the plant plumule to evade hypoxia stress induced by submergence,a condition often arising from overirrigation,ponding,rainstorms,or flooding.While brassinosteroids(BRs)are recognized for their diverse roles in plant growth and development,their influence on coleoptile elongation under hypoxic conditions remains largely unexplored.In this study,we demonstrate the significant requirement of BRs for coleoptile elongation in deep water.During coleoptile development,Glycogen Synthase Kinase3-Like Kinase2(GSK2),the central inhibitor of BR signaling in rice,undergoes substantial suppression in deep water but induction in air.In contrast,the dephosphorylated form of BRASSINAZOLE RESISTANT1(OsBZR1),representing the active form of the key BR signaling transcription factor,is induced in water but suppressed in air.Remarkably,the knockout of GSK3-like kinase genes significantly enhances coleoptile elongation in deep water,strongly indicating a vital contribution of BR response to hypoxia-stimulated coleoptile elongation.Transcriptome analysis uncovers both BR-associated and BR-independent hypoxia responses,implicating substance metabolism,redox reactions,abiotic stress responses,and crosstalk with other hormones in the regulation of BR-induced hypoxia responses.In summary,our findings suggest that rice plumules rapidly elongate coleoptiles through the activation of BR response in deep water,enabling them to escape from submergence-induced hypoxia stress.

The bHLH transcription factor CsPIF4 positively regulates high temperature-induced hypocotyl elongation in cucumber

High temperature-induced hypocotyl elongation is a typical thermomorphogenesis trait that may significantly affect early seedling growth and subsequent crop yield.The ambient temperature and endogenous auxin are two critical factors that regulate hypocotyl growth.However,the mechanism of temperature and auxin integration in horticultural plants remains poorly understood.In this study,the roles of the basic helix-loop-helix transcription factor CsPIF4 in regulating auxin biosynthesis genes and the auxin content in the hypocotyl of cucumber(Cucumis sativus L.)seedlings under high temperature were investigated.qRT-PCR and in situ hybridization analysis revealed that expression of CsPIF4 was enhanced in the epidermis and vascular bundles in the hypocotyl of cucumber seedlings in response to high temperature.qRT-PCR and HPLC analysis showed that CsPIF4 positively regulated transcription of the auxin biosynthesis gene CsYUC8 and the auxin content in the hypocotyl under high temperature(35℃).The CRISPR/Cas9-mediated knockout of CsPIF4 resulted in a shorter hypocotyl compared with that of the wild type,together with decreased expression of CsYUC8 and lower auxin content in response to high temperature.Furthermore,biochemical assays showed that CsPIF4 could bind directly to the G-box motif of the CsYUC8 promoter and thereby activate CsYUC8 expression.These findings provide insight into the molecular mechanism of high temperature-mediated hypocotyl elongation in cucumber.

Lateral root elongation in maize is related to auxin synthesis and transportation mediated by N metabolism under a mixed NO_(3)^(–) and NH_(4)^(+) supply

A mixed nitrate (NO_(3)^(–)) and ammonium (NH_(4)^(+)) supply can promote root growth in maize (Zea mays),however,the changes in root morphology and the related physiological mechanism under different N forms are still unclear.Here,maize seedlings were grown hydroponically with three N supplied in three different forms (NO_(3)^(–)only,75/25 NO_(3)^(–)/NH_(4)^(+)and NH_(4)^(+)only).Compared with sole NO_(3)^(–)or NH_(4)^(+),the mixed N supply increased the total root length of maize but did not affect the number of axial roots.The main reason was the increased total lateral root length,while the average lateral root (LR) length in each axle was only slightly increased.In addition,the average LR density of 2nd whorl crown root under mixed N was also increased.Compared with sole nitrate,mixed N could improve the N metabolism of roots (such as the N influx rate,nitrate reductase (NR) and glutamine synthase (GS)enzyme activities and total amino content of the roots).Experiments with exogenously added NR and GS inhibitors suggested that the increase in the average LR length under mixed N was related to the process of N assimilation,and whether the NR mediated NO synthesis participates in this process needs further exploration.Meanwhile,an investigation of the changes in root-shoot ratio and carbon (C) concentration showed that C transportation from shoots to roots may not be the key factor in mediating lateral root elongation,and the changes in the sugar concentration in roots further proved this conclusion.Furthermore,the synthesis and transportation of auxin in axial roots may play a key role in lateral root elongation,in which the expression of ZmPIN1B and ZmPIN9 may be involved in this pathway.This study preliminarily clarified the changes in root morphology and explored the possible physiological mechanism under a mixed N supply in maize,which may provide some theoretical basis for the cultivation of crop varieties with high N efficiency.

Increased Elongation at Breaking Point with Improved Mechanical Characteristics in PLA

The main goal of this research was to increase the strength of Polylactic acid (PLA), an entirely biodegradable thermoplastic polyester, and an increase in elongation at the breaking point compared to neat PLA. To this end, S1, S2, and S3 were melt blended with various percentages of Zeolite, Glycerol, White vinegar, green camphor, Eucalyptus, and Carom seed oils. Here, the addition of glycerol, eucalyptus, and carom seed oils demonstrated an average improvement in impact and tensile strength of 13.44% and 14.55% respectively. Zeolite and glycerol work together as binding agents to improve stress transfer in the matrix, which increases tensile and flexural modulus as well as toughness elongation (>10%). The addition of the aforementioned materials led to an increase in the glass transition temperature and melting temperature, according to further DSC investigation. The thermal stability increased gradually, according to TGA data.

A homeodomain-leucine zipper I transcription factor, MeHDZ14,regulates internode elongation and leaf rolling in cassava(Manihot esculenta Crantz)

Drought stress impairs plant growth and other physiological functions. MeHDZ14, a homeodomainleucine zipper I transcription factor, is strongly induced by drought stress in various cassava cultivars.However, the role of MeHDZ14 in cassava growth regulation has remained unclear. Here we report that MeHDZ14 affected plant height, such that a dwarf phenotype and altered internode elongation were observed in transgenic cassava lines. MeHDZ14 was found to negatively regulate the biosynthesis of lignin. Its overexpression resulted in abaxially rolled leaves. The morphogenesis of leaf epidermal cells was inhibited by overexpression of MeHDZ14, with decreased auxin and gibberellin and increased cytokinin contents. MeHDZ14 was found to regulate many drought-responsive genes, including genes involved in cell wall synthesis and expansion. MeHDZ14 bound to the promoter of caffeic acid 3-Omethyltransferase 1(MeCOMT1), acting as a transcriptional repressor of genes involved in cell wall development. MeHDZ14 appears to act as a negative regulator of internode elongation and epidermal cell morphogenesis during cassava leaf development.

GhIQD10 interacts with GhCaM7 to control cotton fiber elongation via calcium signaling

IQ67-domain(IQD)proteins function in plant defense and in organ development.The mechanisms by which they influence cotton fiber development are unknown.In the present study,GhIQD10 was expressed mainly in the transition period of cotton fiber development,and GhIQD10-overexpression lines showed shorter fibers.GhIQD10 interacted with GhCaM7 and the interaction was inhibited by Ca^(2+).In in vitro ovule culture,Ca^(2+)rescued the shorter-fiber phenotype of GhIQD10-overexpression lines,which were insensitive to the Ca^(2+)channel inhibitor verapamil and the Ca^(2+)pool release channel blocker 2-aminoethoxydiphenyl borate.We conclude that GhIQD10 affects cotton fiber elongation via Ca^(2+)signaling by interacting with GhCaM7.Brassinosteroid(BR)biosynthesis and signaling genes were up-regulated in GhIQD10-overexpression lines.Fiber development in these lines was not affected by epibrassinolide or the BR biosynthesis inhibitor brassinozole,indicating that the influence of GhIQD10 on fiber elongation was not associated with BR.

Analyses and identifications of quantitative trait loci and candidate genes controlling mesocotyl elongation in rice

Rice direct seeding has the significant potential to save labor and water,conserve environmental resources,and reduce greenhouse gas emissions tremendously.Therefore,rice direct seeding is becoming the major cultivation technology applied to rice production in many countries.Identifying and utilizing genes controlling mesocotyl elongation is an effective approach to accelerate breeding procedures and meet the requirements for direct-seeded rice(DSR) production.This study used a permanent mapping population with 144 recombinant inbred lines(RILs) and 2 828 bin-markers to detect quantitative trait loci(QTLs) associated with mesocotyl length in 2019 and 2020.The mesocotyl lengths of the rice RILs and their parents,Lijiangxintuanheigu(LTH) and Shennong 265(SN265),were measured in a growth chamber at 30°C in a dark environment.A total of 16 QTLs for mesocotyl length were identified on chromosomes 1(2),2(4),3(2),4,5,6,7,9,11(2),and 12.Seven of these QTLs,including qML1a,qML1b,qML2d,qML3a,qML3b,qML5,and qML11b,were reproducibly detected in both years via the interval mapping method.The major QTL,qML3a,was reidentified in two years via the composite interval mapping method.A total of 10 to 413 annotated genes for each QTL were identified in their smallest genetic intervals of 37.69 kb to 2.78 Mb,respectively.Thirteen predicted genes within a relatively small genetic interval(88.18 kb) of the major mesocotyl elongation QTL,qML3a,were more thoroughly analyzed.Finally,the coding DNA sequence variations among SN265,LTH,and Nipponbare indicated that the LOC_Os03g50550 gene was the strongest candidate gene for the qML3a QTL controlling the mesocotyl elongation.This LOC_Os03g50550 gene encodes a mitogen-activated protein kinase.Relative gene expression analysis using qRT-RCR further revealed that the expression levels of the LOC_Os03g50550 gene in the mesocotyl of LTH were significantly lower than in the mesocotyl of SN265.In conclusion,these results further strengthen our knowledge about rice’s genetic mechanisms of mesocotyl elongation.This investigation’s discoveries will help to accelerate breeding programs for new DSR variety development.

ZmMs33 promotes anther elongation via modulating cell elongation regulators,metabolic homeostasis,and cell wall remodeling in maize

Plant cell elongation depends on well-defined gene regulations,adequate nutrients,and timely cell wall modifications.Anther size is positively correlated with the number and viability of pollen grains,while little is known about molecular mechanisms underlying anther cell elongation.Here,we found that properly activated cell elongation regulators at transcriptional levels in loss-of-function ZmMs33 mutant(ms33-6038)anthers failed to promote maize anther elongation.ZmMs33 deficiency disrupted metabolic homeostasis mainly by inhibiting both photosynthesis in anther endothecium and lipid accumulation in anther tapetum.Importantly,ms33-6038 anthers displayed ectopic,premature and excessive secondary cell wall thickening in anther middle layer,which constrained cell elongation structurally and blocked nutrient flows across different anther wall layers.The metabolic disorder was only found in ms33-6038 mutant rather than several representative male-sterility lines at transcriptional and post-translational levels.Collectively,the disordered metabolisms and blocked nutrient flows defeated the activated cell elongation regulators,and finally inhibited anther elongation and growth with a unique‘‘idling effect”in ms33-6038 mutant.

Fiber-specific increase of carotenoid content promotes cotton fiber elongation by increasing abscisic acid and ethylene biosynthesis

Cotton fiber is a raw material for the global textile industry and fiber quality is essential to its industrial application.Carotenoids are plant secondary metabolites that may serve as dietary components,regulate light harvesting,and scavenge reactive oxygen species.Although carotenoids accumulate predominantly in rapidly elongating cotton fibers,their roles in cotton fiber development remain poorly understood.In this study,a fiber-specific promoter proSCFP was applied to drive the expression of GhOR1Del,a positive regulator of carotenoid accumulation,to upregulate the carotenoid level in cotton fiber in planta.Fiber length,strength,and fineness were increased in proSCFP:GhOR1Del transgenic cotton and abscisic acid(ABA)and ethylene contents were increased in elongating fibers.The ABA downstream regulator GhbZIP27a stimulated the expression of the ethylene synthase gene GhACO3 by binding to its promoter,suggesting that ABA promoted fiber elongation by increasing ethylene production.These findings suggest the involvement of carotenoids and ABA signaling in promoting cotton fiber elongation and provide a strategy for improving cotton fiber quality.

The Cotton GhWRKY91 Gene Negatively Regulates Root Elongation in Overexpressed Transgenic Arabidopsis thaliana

WRKY transcription factors play important roles in plant growth,development,and stress responses.Our previous research has shown that the GhWRKY91 gene can delay age-,abscisic acid(ABA)-,and drought-induced leaf senescence when overexpressed in transgenic Arabidopsis plants.To explore in more depth the biological functions of the GhWRKY91 gene,we further observed the root growth of overexpressing transgenic Arabidopsis thaliana under ABA and drought treatment.In this study,we transplanted the germinated seeds of wild-type(WT)and three transgenic lines(OE-12,OE-13 and OE-20)to 1/2 MS solid medium containing ABA and different concentrations of mannitol(simulated drought treatment)for culturing.The results showed that the transgenic plants had dark green leaves and short root lengths when no stress treatment was added.After ABA and mannitol treatment,the root growth of the WT and transgenic Arabidopsis was inhibited to varying degrees,and the root length downregulation of the transgenic plants was higher than that of the WT,indicating that they were more sensitive to ABA and drought.A bimolecular fluorescence complementation(BiFC)assay showed that the GhWRKY91 and GhWRKY3 proteins interact and emit yellow fluorescence in tobacco leaf cells.These results indicate that the GhWRKY91 gene negatively regulates root elongation in transgenic Arabidopsis and provide a basis for further research on the molecular mechanism of its involvement in regulating cotton root development.

Investigation into a practical approach and application of cotton fiber elongation

Background The strength of cotton fiber has been extensively studied and significantly improved through selec-tive breeding,but fiber elongation has largely been ignored,even though elongation contributes to determining the energy needed to break fibers.Recent developments to calibrate the high volume instrument(HVI)for elongation has renewed interest in elongation.However,it is not understood how best to utilize yet another fiber property which has the potential to add to the complexity of fiber selection.To explore a practical approach to applying elongation,cot-ton samples were tested using single fiber methods,the Stelometer,and the HVI.Comparison of strength,elongation,and combined properties such as modulus were explored.Results HVI testing was shown to be sensitive enough to characterize elongation differences but unlike single fiber testing it was unable to capture within-sample variation.Fiber bundle testing,like Stelometer and HVI was shown to reduce bias due to fiber selection.Conclusion The use of secant modulus,an intrinsic material property,allowed for one value to represent both strength and elongation.Secant modulus was shown to contain more useful information than either elongation or work-to-break.Work-to-break was shown to be more influenced by a specific value of breaking force or elongation rather than the intrinsic behavior of the sample being tested.Exploring the influence of genetics and environment on elongation,and its interaction with other fiber properties,requires additional work.Secant modulus,by combining strength and elongation into one value,shows the potential to incorporate elongation values into fiber characteriza-tion without increasing the complexity of current fiber selection processes.

Prokaryotic Expression of Rubber Elongation Factor Gene and Preparation of Its Polyclonal Antibody

[Objective] The aim of this study was to prepare the recombination protein of rubber elongation factor and its polyclonal antibodies.[Method] The encoding gene of rubber elongation factor(REF)was amplified by RT-PCR,and cloned into the prokaryotic expression vector pDEST17 to transform into Escherichia coil BI2I-AI.The recombinant protein induced by L-Arabinose was purified by the affinity chromatography.As the immunogen,the recombination protein was used to immunize mice for preparing polyclonal antibodies,while ELISA and Western blot hybridization were used to detect the titers and specificity.[Result] The purified recombination protein of REF with high expression was used to immunize house mice for preparing polyclonal antibodies with high titer and specificity.The western blot hybridization showed that the antibody could recognize the natural REF from latex.[Conclusion] The recombination protein of REF was successfully obtained and the mouse anti REF antibody with high titer and specificity was prepared,which lays a basis for further studies on biological functions of rubber elongation factor and other membrane proteins in rubber particles.

Inducible Expression of Translation Elongation Factor 1A Gene in Rice Seedlings in Response to Environmental Stresses

Differences of gene expression between salinity_stressed and control rice ( Oryza sativa L. ssp. indica ) cultivar “Zhaiyeqing 8' were compared using differential display PCR (DD_PCR) technique. Sequence analysis of one salt_inducible cDNA clone revealed that this clone represented a new member of rice translation elongation factor 1A (eEF1A) gene family and was tentatively named REF1A. Northern blot hybridization using REF1A fragment as a probe was performed to investigate the expression of rice translation elongation factor 1A gene in response to various environmental factors. It was observed that expression of the eEF1A gene in rice shoots was dramatically induced by salinity stress or exogenous application of abscisic acid (ABA). The induction of this gene by ABA stress occurred more quickly than that by salinity stress. In addition, expression of rice translation elongation factor 1A gene was also induced by drought (15% PEG6000), cold (4 ℃) or heat_shock (37 ℃) stresses. The results suggested that the induction of translation elongation factor 1A gene expression by environmental stresses might reflect the general adaptive response of rice plants to the adverse circumstances.

Tolerance of Salix matsudana to Heavy Metals Determined by Root Elongation Method

[Objective]The research aimed to discuss the tolerance of Salix matsudana to single or compound heavy metals and provide theoretical basis for renovating polluted soil by heavy metals with woody plants.[Method]Using root elongation method,the effects of heavy metal Cu^2＋,Pb^2＋,Zn^2＋ and their mixed solution on the adventitious roots growth of S.matsudana cuttings were studied.[Result]The adventitious roots growth of S.matsudana cuttings was obviously affected by different concentrations of heavy metals solution.Adventitious roots of S.matsudana cuttings could not grow while the concentration of Cu^2＋ was higher than 15 mg/L,the mixture solution concentration was higher than 20 mg/L and Zn^2＋ concentration was higher than 30 mg/L.When the solution concentration reached 40 mg/L,adventitious roots of S.matsudana cuttings could grow only in Pb^2＋ treatment group.With the increasing of the solution concentration,the number of adventitious roots of S.matsudana cuttings gradually decreased.In 5 mg/L Zn^2＋ treatment group,the number of adventitious roots of S.matsudana cuttings was the most,the longest root length and average root length were the longest and the rooting rate was the highest.[Conclusion]The tolerance of S.matsudana to Pb^2＋ was strongest and its tolerance to Cu^2＋ was the weakest.The tolerance order of S.matsudana to three kinds of heavy metals and their mixed solution was as following：Pb^2＋〉Zn^2＋〉Cu^2＋＋Pb^2＋＋Zn^2＋〉Cu^2＋.

Convergence Proving of the Theoretical&True Elongation Inequalities by Derivation and Analogy

According to LN?,theoretical&true elongation of tensile,and by adopting the increasing function of formulas with the derivation and analogy methods,the elongation formula of 0<(1+ε)^1/ε<e&0<ε^1/ε<1&four convergences are deduced too whenε>1 and 0<ε<1.The inequalities of LNε<εand LN(1+ε)<εand LN(1+ε)>LNεare deduced ifε>1 and 0<ε<1 in material dynamics.Finally the conclusions of LNε<εand LNε<LN(1+ε)<εare deduced together ifε>1 and 0<ε<1.

Gene expression and metabolite profiles of cotton fiber during cell elongation and secondary cell wall synthesis

Cotton fibers elongate rapidly after initiation of elongation, eventually leading to the deposit of a large amount of cellulose. To reveal features of cotton fiber cells at the fast elongation and the secondary cell wall synthesis stages, we compared the respective transcriptomes and metabolite profiles. Comparative analysis of transcriptomes by cDNA array identified 633 genes that were differentially regulated during fiber development. Principal component analysis （PCA） using expressed genes as variables divided fiber samples into four groups, which are diagnostic of developmental stages. Similar grouping results are also found if we use non-polar or polar metabolites as variables for PCA of developing fibers. Auxin signaling, wall-loosening and lipid metabolism are highly active during fiber elongation, whereas cellulose biosynthesis is predominant and many other metabolic pathways are downregulated at the secondary cell wall synthesis stage. Transcript and metabolite profiles and enzyme activities are consistent in demonstrating a specialization process of cotton fiber development toward cellulose synthesis. These data demonstrate that cotton fiber cell at a certain stage has its own unique feature, and developmental stages of cotton fiber cells can be distinguished by their transcript and metabolite profiles. During the secondary cell wall synthesis stage, metabolic pathways are streamed into cellulose synthesis.

The tumor-selective over-expression of the human Hsp 70 gene is attributed to the aberrant controls at both initiation and elongation levels of transcription

The tumor selective over-expression of the human Hsp70 gene has been well documented in human tumors,linked to the poor prognosis,being refractory to chemo-and radio-therapies as well as the advanced stage of tumorous lesions in particular.However,both the nature and details of aberrations in the control of the Hsp70 expression in tumor remain enigmatic.By comparing various upstream segments of the Hsp70 gene for each''s ability to drive the luciferase reporter genes in the context of the tumor cell lines varying in their p53 status and an immortal normal liver cell line,we demonstrated in a great detail the defects in the control mechanisms at the both initiation and elongation levels of transcription being instrumental to the tumor selective profile of its expression.Our data should not only offer new insights into our understanding of the tumor specific over-expression of the human Hsp70 gene,but also paved the way for the rational utilization of the tumor selective mechanism with the Hsp70 at the central stage fortargeting the therapeutic gene expression to human tumors.