Elevated O3 alters soil bacterial and fungal communities and the dynamics of carbon and nitrogen.

Although many studies have reported the negative effects of elevated O3 on plant physiological characteristics, the influence of elevated O3 on below-ground processes and soil microbial functioning is less studied. In this study, we examined the effects of elevated O3 on soil properties, soil microbial biomass, as well as microbial community composition using high-throughput sequencing. Throughout one growing season, one-year old seedlings of two important endemic trees in subtropical China: Taxus chinensis (Pilger) Rehd. var. chinensis, and Machilus ichangensis Rehd. Et Wils, were exposed to charcoal-filtered air (CF as control), 100 nl l-1 (E100) or 150 nl l-1 (E150) O3-enriched air, in open top chambers (OTCs). We found that only higher O3 exposure (E150) significantly decreased soil microbial biomass carbon and nitrogen in M. ichangensis, and the contents of organic matter were significantly decreased by E150 in both tree species. Although both levels of O3 exposure decreased NO3-N in T. chinensis, only E150 increased NO3-N in M. ichangensis, and there were no effects of O3 on NH4-N. Moreover, elevated O3 elicited changes in soil microbial community structure and decreased fungal diversity in both M. ichangensis and T. chinensis. However, even though O3 exposure reduced bacterial diversity in M. ichangensis, no effect of O3 exposure on bacterial diversity was detected in soil grown with T. chinensis. Our results showed that elevated O3 altered the abundance of bacteria and fungi in general, and in particular reduced nitrifiers and increased the relative abundance of some fungal taxa capable of denitrification, which may stimulate N2O emissions. Overall, our findings indicate that elevated O3 not only impacts the soil microbial community structure, but may also exert an influence on the functioning of microbial communities.

Effects of elevated O3 on physiological and biochemical responses in three kinds of trees native to subtropical forest in China during non-growing period.

Numerous studies have documented the negative effects of ozone (O3) on tree species in growing season, however, little is done in non-growing season. Three evergreen tree species, Phoebe bournei (Hemsl.) Yang (P. bournei), Machilus pauhoi Kanehira (M. pauhoi) and Taxus chinensis (Pilger) Rehd (T. chinensis), were exposed to non-filtered air, 100 nmol mol-1 O3 air (E1) and 150 nmol mol-1 O3 air (E2) in open-top chambers in subtropical China. In the entire period of experiment, O3 fumigation decreased net photosynthesis rate (Pn) through stomatal limitation during the transition period from growing to non-growing season (TGN), and through non-stomatal limitation during the period of non-growing season (NGS) in all species tested. Meanwhile, O3 fumigation reduced and delayed the resilience of Pn in all species tested during the transition period from non-growing to growing season (TNG). O3 fumigation significantly decreased chlorophyll contents during NGS, whereas no obvious injury symptoms were observed till the end of experiment. O3 fumigation induced increases in levels of malondialdehyde, superoxide dismutase, total phenolics and reduced ascorbic acid, and changes in four plant endogenous hormones as well in all species tested during NGS. During NGS, E1 and E2 reduced Pn by an average of 80.11% in P. bournei, 94.56% in M. pauhoi and 12.57% in T. chinensis, indicating that the O3 sensitivity was in an order of M. pauhoi > P. bournei > T. chinensis. Overall, O3 fumigation inhibited carbon fixation in all species tested during NGS. Furthermore, O3-induced physiological activities also consumed the dry matter. All these suggested that elevated O3, which is likely to come true during NGS in the future, will adversely affect the accumulation of dry matter and the resilience of Pn during TNG in evergreen tree species, and further inhibit their growth and development in the upcoming growing season.

Molecular, structural, and phylogenetic analyses of Taxus chinensis JAZs.

Taxus spp. are ancient gymnosperms that produce a unique secondary metabolite, namely, taxol, an anticancer drug. JAZ proteins are key regulators of the JA signaling pathway, which control taxol biosynthesis. However, the JAZ proteins of Taxus spp. are poorly studied. In this work, nine JAZ genes from Taxus chinensis were identified using our previous transcriptome data and named as TcJAZ1-TcJAZ9. Of these nine TcJAZ proteins, eight contain Jas and TIFY domains, and the Jas domain of TcJAZ6 is incomplete. Most TcJAZs and PsJAZs are not related to AtJAZs and OsJAZs. Phylogenetic analysis divided all JAZ proteins from Arabidopsis thaliana, Oryza sativa, Picea sitchensis, and T. chinensis into eight subgroups; gymnosperms JAZs were classified into subgroups V-VIII, and angiosperm JAZs were categorized into subgroups I-V. Three motifs of subgroups VI-VIII were identified in gymnosperm JAZs, indicating that gymnosperm JAZ proteins exhibit a different evolutionary process from those of angiosperms. The expression patterns of nine TcJAZs showed that TcJAZ2/3/8 was a key regulator, indicating their important roles in T. chinensis. Results revealed that gymnosperm JAZs differ from angiosperm JAZs in terms of molecular structure. Three novel conserved motifs were found in TcJAZs and PsJAZs. This study provides a basis for research on JA regulatory system in Taxus spp. and for elucidating the significance of JA signaling pathway to land plants.

Transcript profiling of jasmonate-elicited Taxus cells reveals a ß-phenylalanine-CoA ligase.

Plant cell cultures constitute eco-friendly biotechnological platforms for the production of plant secondary metabolites with pharmacological activities, as well as a suitable system for extending our knowledge of secondary metabolism. Despite the high added value of taxol and the importance of taxanes as anticancer compounds, several aspects of their biosynthesis remain unknown. In this work, a genomewide expression analysis of jasmonate-elicited Taxus baccata cell cultures by complementary DNA-amplified fragment length polymorphism (cDNA-AFLP) indicated a correlation between an extensive elicitor-induced genetic reprogramming and increased taxane production in the targeted cultures. Subsequent in silico analysis allowed us to identify 15 genes with a jasmonate-induced differential expression as putative candidates for genes encoding enzymes involved in five unknown steps of taxane biosynthesis. Among them, the TB768 gene showed a strong homology, including a very similar predicted 3D structure, with other genes previously reported to encode acyl-CoA ligases, thus suggesting a role in the formation of the taxol lateral chain. Functional analysis confirmed that the TB768 gene encodes an acyl-CoA ligase that localizes to the cytoplasm and is able to convert ß-phenylalanine, as well as coumaric acid, into their respective derivative CoA esters. ß-phenylalanyl-CoA is attached to baccatin III in one of the last steps of the taxol biosynthetic pathway. The identification of this gene will contribute to the establishment of sustainable taxol production systems through metabolic engineering or synthetic biology approaches.

Expression of recombinant alpha and beta tubulins from the yew Taxus cuspidata and analysis of the microtubule assembly in the presence of taxol.

Taxol was originally isolated from the yew Taxus brevifolia. Because taxol inhibits the depolymerization of microtubules, the presence of a self-resistance mechanism in Taxus spp. was hypothesized. The cloning of the cDNA for alpha and beta tubulins from Taxus cuspidata and those from the human embryonic kidney cell line HEK293T revealed that the (26)Asp, (359)Arg, and (361)Leu residues in the human beta tubulin, which are important for taxol binding, were replaced with Glu, Trp, and Met in the beta tubulin of T. cuspidata, respectively. The microtubule assembly of the recombinant alpha and beta tubulins was monitored turbidimetrically, and the results clearly demonstrated that the microtubule from T. cuspidata is less sensitive to taxol than that from HEK293T cells. The Taxus microtubule composed of the wild-type alpha tubulin and the beta tubulin with the E26D mutation restored the sensitivity to taxol. We thus postulated that the mutation identified in the beta tubulin of T. cuspidata plays a role in the self-resistance of this species against taxol.

Synergistic effect of cyclodextrins and methyl jasmonate on taxane production in Taxus x media cell cultures.

Methyl jasmonate and cyclodextrins are proven effective inducers of secondary metabolism in plant cell cultures. Cyclodextrins, which are cyclic oligosaccharides, can form inclusion complexes with nonhydrophilic secondary products, thus increasing their excretion from the producer cells to the culture medium. In the present work, using a selected Taxus x media cell line cultured in a two-stage system, the relationship between taxane production and the transcript profiles of several genes involved in taxol metabolism was studied to gain more insight into the mechanism by which these two elicitors regulate the biosynthesis and excretion of taxol and related taxanes. Gene expression was not clearly enhanced by the presence of cyclodextrins in the culture medium and variably induced by methyl jasmonate, but when the culture was supplemented with both elicitors, a synergistic effect on transcript accumulation was observed. The BAPT and DBTNBT genes, which encode the last two transferases involved in the taxol pathway, appeared to control limiting biosynthetic steps. In the cell cultures treated with both elicitors, the produced taxanes were found mainly in the culture medium, which limited retroinhibition processes and taxane toxicity for the producer cells. The expression level of a putative ABC gene was found to have increased, suggesting it played a role in the taxane excretion. Taxol biosynthesis was clearly increased by the joint action of methyl jasmonate and cyclodextrins, reaching production levels 55 times higher than in nonelicited cultures.

Methyl jasmonate represses growth and affects cell cycle progression in cultured Taxus cells.

KEY MESSAGE: Methyl jasmonate elicitation of Taxus cultures enhances paclitaxel accumulation, but represses growth by inhibition of cell cycle progression. Growth repression is evident both at the culture level and transcriptional level. Methyl jasmonate (MeJA) elicitation is an effective strategy to induce and enhance synthesis of the anticancer agent paclitaxel (Taxol(®)) in Taxus cell suspension cultures; however, concurrent decreases in growth are often observed, which is problematic for large-scale bioprocessing. Here, increased accumulation of paclitaxel in Taxus cuspidata suspension cultures with MeJA elicitation was accompanied by a concomitant decrease in cell growth, evident within the first 3 days post-elicitation. Both MeJA-elicited and mock-elicited cultures exhibited similar viability with no apoptosis up to day 16 and day 24 of the cell culture period, respectively, suggesting that growth repression is not attributable to cell death. Flow cytometric analyses demonstrated that MeJA perturbed cell cycle progression of asynchronously dividing Taxus cells. MeJA slowed down cell cycle progression, impaired the G1/S transition as observed by an increase in G0/G1 phase cells, and decreased the number of actively dividing cells. Through a combination of deep sequencing and gene expression analyses, the expression status of Taxus cell cycle-associated genes correlated with observations at the culture level. Results from this study provide valuable insight into the mechanisms governing MeJA perception and subsequent events leading to repression of Taxus cell growth.

Correlation analysis of the taxane core functional group modification, enzyme expression, and metabolite accumulation profiles under methyl jasmonate treatment.

Metabolomic and transcriptomic profiling data were obtained and integrated to elucidate the crucial network controls on taxol and its precursor biosynthesis during the taxane core functionalization within methyl jasmonate (MJ)-induced Taxus chinensis cells. Twelve metabolites were identified using liquid chromatography-electrospray ionization-mass spectrometry. These metabolites contain taxol (paclitaxel), baccatin III (B-III) and its analogs, a group structurally bearing multiple free hydroxyls (TAX), and another group of multiple acyl taxanes (MAT), including taxuyunnanine C (TC) and its analogs. The metabolomic profile showed a higher increase in TAX than in MAT. Particularly, the ratio of B-III and taxol to the total taxane content increased more significantly in TAX than in MAT. The MAT proportion did not significantly change, although they are predominant components in cell cultures compared with TAX. Quantitative real-time polymerase chain reaction (qRT-RCR) was used to determine the transcription level of 20 genes, among which 11 were reported responsible for taxol biosynthesis and 9 were obtained from our previous transcriptomic data. The total expression levels of hydroxylase after 24 h and 6 days were higher than those of acylase. The principal component analysis (PCA) results validated the metabolomic analysis data, indicating that hydroxylation was more crucial than acylation for controlling the flux toward TAX biosynthesis. Furthermore, the PCA contribution comparison showed that two undefined genes of OHX1 and ACX3 might have good potential in TAX upregulation and MAT downregulation. To the best of our knowledge, this study provides the first experimental evidence on the contribution of total hydroxylation to taxane biosynthesis.

Functional analysis of a WRKY transcription factor involved in transcriptional activation of the DBAT gene in Taxus chinensis.

Although the regulation of taxol biosynthesis at the transcriptional level remains unclear, 10-deacetylbaccatin III-10 ß-O-acetyl transferase (DBAT) is a critical enzyme in the biosynthesis of taxol. The 1740 bp fragment 5'-flanking sequence of the dbat gene was cloned from Taxus chinensis cells. Important regulatory elements needed for activity of the dbat promoter were located by deletion analyses in T. chinensis cells. A novel WRKY transcription factor, TcWRKY1, was isolated with the yeast one-hybrid system from a T. chinensis cell cDNA library using the important regulatory elements as bait. The gene expression of TcWRKY1 in T. chinensis suspension cells was specifically induced by methyl jasmonate (MeJA). Biochemical analysis indicated that TcWRKY1 protein specifically interacts with the two W-box (TGAC) cis-elements among the important regulatory elements. Overexpression of TcWRKY1 enhanced dbat expression in T. chinensis suspension cells, and RNA interference (RNAi) reduced the level of transcripts of dbat. These results suggest that TcWRKY1 participates in regulation of taxol biosynthesis in T. chinensis cells, and that dbat is a target gene of this transcription factor. This research also provides a potential candidate gene for engineering increased taxol accumulation in Taxus cell cultures.

Enhanced taxane production and secretion from Taxus baccata cell culture by adding dimethylsulfoxide.

The ability of an aprotic solvent, dimethylsulfoxide (DMSO), to induce taxane synthesis and release from cell suspension culture of Taxus baccata was examined. The results showed that applying DMSO in optimal conditions not only led to enhancement in taxane excretion from the cells but also led to improvement in taxol synthesis. Maximum yields for taxol [3.34 mg/g dry cell weight (DCW)] were achieved by adding 5% DMSO to the culture at the late-exponential phase of cell growth (day 14) and culturing for 21 days, which was 2.26-fold of that for the control (1.48 mg/g DCW). However, adding 5% DMSO did not affect the yield of 10-deacetyl baccatin III and baccatin III. This condition also resulted in maximum extracellular taxane (4.86 mg/L); this value was 2.82-fold higher than that in the control (1.72 mg/L). We demonstrated that the late-exponential phase of cell growth could be the best time to add elicitor for maximizing the yield of taxol. Adding DMSO at earlier times (days 1 and 7) or in other concentrations (1% and 3%) had negative effects on taxane synthesis. Overall results suggest that DMSO has good potential to enhance synthesis and release taxol from cell suspension culture of T. baccata L.

[Effects of gathering season and three age affect on main active components of Taxus madia].

OBJECTIVE: To reveal the influence of harvest season and tree age on the content of taxol and 10-DAB III, and provide the basis for the harvest time of Taxus madia. METHOD: Branches and leaves of the labeled 25 three-year-old plants and 25 five-year-old plants were collected every two months from March 26,2009 to January 26, 2010. Taxol and 10-DAB III content of different age and growth season of Taxus in branches were determined by HPLC. RESULT: Taxol and 10-DAB III content were significantly different in different harvesting age. The content of five-year-old plants was significantly higher than that of three-year-old plants. Taxol and 10-DAB III contents were significantly different in different harvesting season, and the highest content of taxol and 10-DAB III was 0.56, 0.32 mg x g(-1), respectively, in May. CONCLUSION: The May is the suitable harvest season for T. madia, but the suitable harvest age need further study which according to the main active component and biomass accumulation.

Taxus globosa S. cell lines: initiation, selection and characterization in terms of growth, and of baccatin III and paclitaxel production.

Of the initial six cell lines originating from explants of Taxus globosa, or Mexican yew (stem internode, leaves and meristematic tissue), three were selected for their microbial and oxidation resistance, two from leaves and the other from stem internode. A study of their behavior, both in terms of cell growth, and of baccatin III and paclitaxel production, was developed in suspension cultures with an initially standardized biomass (fresh weight 0.23 g/L) using modified Gamborg's B5 medium, and an elicitor (methyl jasmonate), on either the first or seventh day of culture, at several levels (0, 0.1, 1, 10, 100 microM). In most of the conditions used, the three cell lines showed growth associated baccatin III production. The cell line from stem internode was the highest producer of baccatin III using 1 microM elicitor, sampling at 10 days (p < or = 0.01, 6.45 mg/L). This same line also had the highest biomass production (6.85 g/L, p < or = 0.01) at 10 days of culture but at the higher elicitor concentration of 10 microM. All three cell lines did not produce paclitaxel under experimental conditions used.

Enhancement of taxane production in hairy root culture of Taxus x media var. Hicksii.

This study assessed the effect of two precursors (l-phenylalanine and p-amino benzoic acid) used alone or in combination with methyl jasmonate, on the growth and accumulation of paclitaxel, baccatin III and 10-deacetylbaccatin III in hairy root cultures of Taxus x media var. Hicksii. The greatest increase in dry biomass was observed after 4 weeks of culturing hairy roots in medium supplemented with 1microM of l-phenylalanine (6.2gL(-1)). Addition of 1microM of l-phenylalanine to the medium also resulted in the greatest 10-deacetylbaccatin III accumulation (422.7microg L(-1)), which was not detected in the untreated control culture. Supplementation with 100microM of l-phenylalanine together with 100microM of methyl jasmonate resulted in the enhancement of paclitaxel production from 40.3microg L(-1) (control untreated culture) to 568.2microg L(-1), the highest paclitaxel content detected in the study. The effect of p-amino benzoic acid on taxane production was less pronounced, and the highest yield of paclitaxel (221.8microg L(-1)) was observed when the medium was supplemented with 100microM of the precursor in combination with methyl jasmonate. Baccatin III was not detected under the conditions used in this experiment and the investigated taxanes were not excreted into the medium.

Effect of taxol feeding on taxol and related taxane production in Taxus baccata suspension cultures.

To achieve a better understanding of taxol metabolism and accumulation in Taxus cell cultures, a T. baccata cell line growing for 20 days in a selected growth medium was treated at the beginning of the experiment with several concentrations of taxol (25, 50, 100 and 200mgL(-1)). Compared with an untreated control, all these taxol concentrations stimulated cell-associated taxol content (up to 32.7 times in the presence of 200mgL(-1) exogenous taxol), although higher concentrations significantly depressed cell viability. DNA laddering analysis revealed that the viability reduction was not related to apoptosis, suggesting that taxol itself was the primary responsible factor. On the basis of RT-PCR expression analysis of genes encoding taxadiene synthase (ts) and 1-deoxy-d-xylulose-5-phosphate synthase (dxs) from treated and nontreated T. baccata cell line cultures, it was observed that exogenous taxol clearly induced the mRNA levels of both taxane-related enzymes. Additionally, we found that exogenous taxol caused a considerable increase in taxadiene synthase activity, although in no case did this coincide with the highest levels of taxol observed at the end of the culture. The effect of exogenous taxol on the content of other related taxanes was also considered.

Lipidomic analysis reveals activation of phospholipid signaling in mechanotransduction of Taxus cuspidata cells in response to shear stress.

Lipid signaling involved in mechanotransduction processes in response to shear stress in plants remained elusive. To understand the responses of phospholipids in shear stress-induced mechanotransduction, a lipidomic approach was employed to profile phospholipid species of Taxus cuspidata cells under laminar shear stress. A total of 99 phospholipid species were profiled quantitatively, using the LC/ESI/MS(n) procedure. Potential biomarkers were found by the principal component analysis (PCA) as well as partial least squares (PLS) combined with variable influence in the projection (VIP). Phosphatidic acid (PA) and lysophosphatidylcholine (LysoPC) were two important lipid groups that were responsible for the discrimination between shear stress induced and control cells. Further research revealed that shear stress enhanced the activation of phospholipase D (PLD) and phospholipase C (PLC) compared with control cells and consequently increased PA content in shear stress induced T. cuspidata cells. These results demonstrate that phospholipids and related phospholipases play important roles in mechanotransduction of T. cuspidata cells in response to shear stress.

Lipidomic analysis reveals differential defense responses of Taxus cuspidata cells to two elicitors, methyl jasmonate and cerium (Ce4+).

Methyl jasmonate (MeJA) and cerium (Ce(4+)) elicitation share common features of increasing taxol accumulation of Taxus cuspidata cells. Interestingly, Ce(4+) induces programmed cell death (PCD), but this phenomenon is not observed with MeJA elicitation. Here, using a lipidomic approach to measure more than 100 membrane glycerophospholipids of T. cuspidata cells quantitatively, we discovered that lysophosphatidylcholine (LysoPC), phosphatidic acid (PA) and phosphatidylcholine were three potential lipid markers that were responsible for the differences between Ce(4+)-induced cells and MeJA-induced cells. Compared with MeJA elicitation, marked increase of phospholipase D (PLD) activity was observed following Ce(4+) elicitation, suggesting that the PLD activation and high concentrations of PA production might mediate the PCD. Rapid increase of phospholipase A(2) (PLA(2)) activity caused the release of fatty acids and LysoPC following Ce(4+) elicitation, which enhanced endogenous jasmonic acid (JA) accumulation. In contrast, PLA(2) activity was poorly induced following MeJA elicitation. PLA(2) inhibitor suppressed not only JA accumulation but also taxol production, suggesting that the PLA(2) activation mediated Ce(4+)-induced taxol production partially through a JA-dependent signaling pathway. These results demonstrate that differential alternation of glycerolphospholipids caused by phospholipases constitutes an important step in cell death response to Ce(4+) and increasing taxol production.

Salicylic acid-induced taxol production and isopentenyl pyrophosphate biosynthesis in suspension cultures of Taxus chinensis var. mairei.

The influences of salicylic acid (SA) on taxol production and isopentenyl pyrophosphate (IPP) biosynthesis pathways in suspension cultures of Taxus chinensis var. mairei were investigated by adding SA and mevastatin (MVS), a highly specific inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase in the mevalonate pathway for IPP biosynthesis, into the culture systems. The cell death and taxol production were induced upon the introduction of SA, and 20mg/l was proved to be the optimal SA concentration in terms of the less damage to Taxus cells and marked activation of phenylalanine ammonia lyase (PAL). In the coexistence of SA (20mg/l) and MVS (100 nmol/l), the taxol content (1.626 mg/g dry wt) was higher than that (0.252 mg/g dry wt) of the MVS-treated system but almost equal to that (1.581 mg/g dry wt) of the SA-treated system. It is thus inferred that the activated non-mevalonate pathway should be responsible for the formation of IPP in taxol biosynthesis in the presence of SA.

RGD-dependent mechanotransduction of suspension cultured Taxus cell in response to shear stress.

Plant cells cultured in bioreactors are strongly influenced by mechanical forces. However, the molecular mechanism of plant cell mechanoreception has maintained unclear. In animal cells, the Arg-Gly-Asp (RGD) motif can be found in proteins of the extracellular matrix. Integrins link the intracellular cytoskeleton of cells with the extracellular matrix by recognizing this RGD motif. Integrin has been demonstrated to function as an apparatus not only for adhesion but also for mechanotransduction. In plant cells, the molecules that mediate the structural continuity between wall and membrane are unknown. Here, we found that synthetic RGD peptide could dramatically reduce the level of phosphorylation of MAPK-like cascades that are activated by shear stress and reduce the alkalinization response, production of reactive oxygen species (ROS) and accumulation of phenolics by Taxus cuspidata cells during shear stress. These results implicate that a RGD recognition system may exist in Taxus cells and play an important role in signal transduction of shear stress. Although the Arabidopsis genome database shows that the plant seems to lack a homologue of animal integrin, plant cells may use other RGD-binding proteins to recognize the RGD motif. The correlative mechanism is discussed.

Stable transformation and long-term maintenance of transgenic Taxus cell suspension cultures.

A cell line of Taxus cuspidata has been transformed with wild-type Agrobacterium rhizogenes ATCC strain 15834 containing binary vector pCAMBIA1301 and, separately, with A. tumefaciens strain EHA105 containing binary vector pCAMBIA1305.2. Additionally, a cell line of T. chinensis has been transformed with wild-type A. rhizogenes ATCC strain 25818 containing binary vector pCAMBIA1301. The two transgenic T. cuspidata cell lines have been maintained in culture for more than 20 months, and the transgenic T. chinensis cell line for more than 9 months, with no loss of reporter gene expression or antibiotic resistance. The introduced genes had no discernable effect on growth or Taxol production in the transgenic cell lines when compared to the parent control. The methods for transforming non-embryogenic Taxus suspension cultures are described.

Development of a culture sub-population induction model: signaling pathways synergy and taxanes production by Taxus canadensis.

Cell cultures of Taxus canadensis were subjected to exogenously applied ethylene (ET) hormone and methyl jasmonate (MJ) elicitation in factorial design experiments. Levels of extracellular taxanes, including paclitaxel, were used with principal component analysis for fault detection and real-coded genetic algorithms for parameter optimization to construct a culture sub-population induction model. Culture sub-populations were identified by the model as (1) uninduced, (2) induced to unilateral function of the ET-signaling pathway, and (3) induced to cooperation between jasmonic acid (JA)- and ET-signaling pathways. Comprehensive model results suggested greater rates of cellular induction (resulting in exogenous taxane production) by ET gas as opposed to MJ elicitation. However, cellular induction of ET-signaling pathway genes increased the rate of induction of JA-signaling pathway genes by orders of magnitude. In addition, model results showed that induction of genes leading to extracellular production of the simple taxane 10-deacetylbaccatin III was regulated by the unilateral ET-signaling pathway. However, it was suggested that further processing of this simple taxane to complex taxane structures, such as paclitaxel, required further gene induction by the JA-signaling pathway. Thus, production rate constants of exogenous complex taxanes were predicted to be an order of magnitude lower than that for the simple taxane 10-deacetylbaccatin III. The fraction of the cell culture sub-population displaying unilateral ET-signaling pathway gene induction was found inversely proportional to levels of MJ elicitation. When coupled with simple non-growth product models, levels of all extracellular taxanes were effectively predicted using the culture sub-population induction model.