Expression Of PDS Research Articles

Physiological response of microalga Dunaliella parva when treated with MeJA, GA3.

DpAP2 is a transcription factor regulating carotenoid biosynthesis pathway. It was speculated that MeJA significantly decreased expression of DpAP2 gene, then the decreasing DpAP2 expression significantly inhibited expression of some key enzyme genes such as PSY, PDS and GGPS in carotenoid biosynthesis pathway. In contrast, it was speculated that GA3 significantly increased expression of DpAP2 gene, then the increasing DpAP2 expression significantly increased expression of some key enzyme genes such as PDS and GGPS in carotenoid biosynthesis pathway. To increase the content of carotenoid, we evaluated the effect of DpAP2 overexpression on carotenoid accumulation in D. parva. Transgenic D. parva showed a higher carotenoid content (3.18 mg/g DW) compared with control group (2.13 mg/g DW) at 9 d. The dosage effects of exogenous hormones MeJA and GA3 were found in D. parva cells treated with different concentrations of MeJA (10, 20, 50, 100 μM) and GA3 (10, 20, 50, 100 μM). The high concentrations of MeJA (10-100 μM) inhibited the accumulation of carotenoid, and the relative expression of DpAP2, PSY, PDS and GGPS decreased significantly. On the contrary, the relative expression of DpAP2, PDS and GGPS increased significantly when D. parva was treated with 10, 20, 50 and 100 μM GA3, which promoted the biosynthesis of carotenoid. Therefore, we inferred that there was a hierarchical regulation from hormone, transcription factor, key enzyme gene to carotenoid accumulation in carotenoid biosynthesis. Carotenoid biosynthesis was enhanced by DpAP2 overexpression (1.4930 fold of control) and exogenous substances such as GA3 (1.5889 fold of control), which laid a foundation for massive accumulation of carotenoids in microalgae. In the future, further studies were required to demonstrate the complex regulatory network.

A comprehensive physiological and -Omic analysis of trypsin-mediated protection of green pepper fruits from chilling injury

Chilling injury (CI) in green pepper fruits during low-temperature storage causes a significant decline in quality. The present study utilized physiological, transcriptomic, and metabolomic analyses to idneitfy the mechanisms by which trypsin mitigates CI in green peppers stored at 4 °C for 8 days, followed by 3 days of shelf life. Results indicated that the trypsin treatment significantly reduced electrolyte leakage and the CI index in peppers, effectively extending their shelf life and preserving postharvest quality. After 4 days of storage, comparative -omic analyses identified 2514 differentially expressed genes (DEGs) and 397 differentially abundant metabolites (DAMs) between trypsin-treated and control peppers. The trypsin treatment induced changes in sugar metabolism, modulating the expression of HK, SUS, INV, and GLGC, which affected the abundance of metabolites such as CDP-glucose and α-D-p-glucose. Trypsin also enhanced carotenoid metabolism, altering the abundance of rhodopinal glucoside, 1′-hydroxyl-γ-carotene glucoside, and farnesyl 1-PP, and influencing the expression of PDS, CRTH, CRTB, and LUT5. Notably, the trypsin treatment activated the mitogen-activated protein kinase (MAPK) pathway that plays an integral role in the signal transduction of abiotic stress. Differential expression of FLS2, ELF18, PTO, PR1, PTI5, WPKY, MEKK1, and MPK6 genes in the MAPK pathway was observed, which was correlated with CI mitigation in green peppers during cold storage. In conclusion, trypsin is an effective treatment for reducing CI in green peppers during cold storage. The present study provides valuable insights into its physiological and molecular impact on green pepper fruit.

A D-cysteine desulfhydrase, SlDCD2, participates in tomato fruit ripening by modulating ROS homoeostasis and ethylene biosynthesis.

Hydrogen sulfide (H2S) is involved in multiple processes during plant growth and development. D-cysteine desulfhydrase (DCD) can produce H2S with D-cysteine as the substrate; however, the potential developmental roles of DCD have not been explored during the tomato lifecycle. In the present study, SlDCD2 showed increasing expression during fruit ripening. Compared with the control fruits, the silencing of SlDCD2 by pTRV2-SlDCD2 accelerated fruit ripening. A SlDCD2 gene-edited mutant was constructed by CRISPR/Cas9 transformation, and the mutant exhibited accelerated fruit ripening, decreased H2S release, higher totalcysteine and ethylene contents, enhanced chlorophyll degradation and increased carotenoid accumulation. Additionally, the expression of multiple ripening-related genes, including NYC1, PAO, SGR1, PDS, PSY1, ACO1, ACS2, E4, CEL2, and EXP was enhanced during the dcd2 mutant tomato fruit ripening. Compared with the wild-type fruits, SlDCD2 mutation induced H2O2 and malondialdehyde (MDA) accumulation in fruits, which led to an imbalance in reactive oxygen species (ROS) metabolism. A correlation analysis indicated that H2O2 content was strongly positively correlated with carotenoids content, ethylene content and ripening-related gene expression and negatively correlated with the chlorophyll content. Additionally, the dcd2 mutant showed earlier leaf senescence, which may be due to disturbed ROS homeostasis. In short, our findings show that SlDCD2 is involved in H2S generation and that the reduction in endogenous H2S production in the dcd2 mutant causes accelerated fruit ripening and premature leaf senescence. Additionally, decreased H2S in the dcd2 mutant causes excessive H2O2 accumulation and increased ethylene release, suggesting a role of H2S and SlDCD2 in modulating ROS homeostasis and ethylene biosynthesis.

Mechanism of development of residual goitre and associated thyroid disorders

In post salt iodination period, endemic goiter that generally develops for iodine deficiency is found prevalent in many regions, including India, despite adequate iodine intake. Such goiters are termed as residual goiters. Consumption of dietary goitrogens could be the possible regulator in the persistence of residual goitre and associated disorders. Residual goitres exist in Manipur, India for the consumption of bamboo shoots (BS). Therefore, to study the actions of BS on major thyroid hormone synthesizing regulatory factors at cellular and molecular levels on isolated thyrocytes conducted perusing expression of NIS, TPO, Tg and PDS proteins as well as mRNA and protein expression of NIS, TPO, Tg, PDS, MCT8 and PAX8 with and without extra iodine in in-vitro studies. Simultaneously, ROS generation in terms of H2O2 and antioxidant status, NO, LPO were assayed. Cellular and DNA damage and oxidation, including cell cycle alterations after BS exposure, were also investigated. Precursors and metabolic end products of cyanogenic glycosides on phytochemical analysis found in BS. It has pleiotropic effects on thyrocytes. It repressed the activities of Na+-K+-ATPase, TPO and D2, as well as reduced the expression of NIS, TPO, Tg, PDS proteins and MCT8 and PAX8, at mRNA level. All these effects of BS are mediated through increased ROS levels as H2O2 upsurge leading to a perturbed pro-oxidant antioxidant balance in thyrocytes associated with cellular and DNA damage and oxidation. Increased LPO and NO levels upon exposure of BS extract triggered plasma membrane and organelle damage of thyrocytes, which are major sites of NIS, TPO, PDS and MCT8, leading to thyroid disfunction. Cellular and DNA damage/oxidation was observed that leads to disruption of normal cell cycle pattern of thyrocytes which in turn causes changes in apoptotic proteins Bax, Bcl-2 and p53. These changes imply imbalance of cell death and proliferation equilibrium leading to disease conditions as found in goitre upon exposure to BS extract. Extra iodine prevents goitrogenic/anti-thyroid influences of BS on such actions to an extent. Thyroid diseases among residual goitrous population following consumption of BS evaluated by their iodine nutritional and salt iodization status, serumT3, T4 and TSH profiles, TPO- and Tg-Ab antibodies, thyroid ultrasonography, the prevalence of hypo- and hyperthyroidism and cytomorphological features. Goitrous populations are affected by subclinical and overt hypo- and hyperthyroidism with elevated thyroid autoantibodies, hypoechoic thyroid and thyroiditis. This study concludes that residual goitrous individuals are affected by different autoimmune thyroid disorders. Excess thiocyanate from dietary goitrogens of cyanogenic origin (BS) is responsible for the development of residual goitre followed by its progression towards different thyroid autoimmune disorders.

CPTA treatment reveals potential transcription factors associated with carotenoid metabolism in flowers of Osmanthus fragrans

Osmanthus fragrans is one of the top ten traditional flowers in China. It is divided into three different groups according to its color. α-Carotene and β-carotene are the main determinants to distinguish the color differences between three groups. However, the dominant genes and transcription factors involved in carotenoid metabolism remain unclear. CPTA treatment (0.7 mmol · L−1) remarkably promoted lycopene, α-carotene and β-carotene contents in flowers. Transcriptome sequencing analysis revealed that CPTA treatment could trigger chain reactions in carotenoid metabolism pathway genes. Four up-regulated and 10 down-regulated transcription factors which have close association with carotenoid variation were significantly induced by CPTA treatment. The up-regulated TFs such as MYB43, MYB123, HSF, were further subjected to transcript expression determination in different cultivars with drastic colors. Among them, transcript expression of four up-regulated TFs coincided with the carotenoid accumulation in different cultivars. We selected up-regulated OfMYB43 to verify its function, which is related to stress tolerance and transcriptional regulation. Transient overexpression of OfMYB43 in O. fragrans flowers showed that it could remarkably promote the expression of PDS, ZISO, LCYE and CCD4, leading to increased accumulation of β-branch carotenoids. OfMYB43 was a potential positive regulator of carotenoid biosynthesis in O. fragrans flowers. This study provides insight into the molecular mechanism of carotenoid metabolism in O. fragrans.

RNAi silenced ζ-carotene desaturase developed variegated tomato transformants with increased phytoene content

ζ-carotene desaturase (ZDS) is one of the enzymes that catalyzes the conversion of ζ-carotene to lycopene. However, the role of ZDS has been not studied extensively in tomato. In this study, to examine the role of ZDS in tomato, the expression of ZDS was downregulated by RNA interference. The relative mRNA levels of ZDS in RNAi lines were reduced by more than 75% compared to wild-type plants. The genetically modified plants exhibited altered morphological characteristics such as photobleached leaves, increased leaf length, longer petioles, larger leaf surface areas and whitish-green tomato fruits. Chromatographic determination showed a significant increase in phytoene in both leaves and fruits of the RI lines, whereas other types of carotenoids were significantly decreased compared to controls. qPCR analysis revealed significant changes in the expression of PSY, PDS and LCYB. The endogenous hormones and flavonoid levels were altered in leaves and fruits of ZDS-silenced plants. Electron microscopic studies revealed hampered chloroplast differentiation and disrupted thylakoid structure in the ZDS-suppressed lines. GC–MS analysis showed that the level of several organic acids, amino acids and fatty acids were decreased in the RI lines, whereas the sugars and sugar derivatives were slightly increased compared to controls. Thus, these results imply a potential for ZDS in carotenoid enhancement through genetic engineering of the carotenoid pathway.

Possible mechanism of bamboo shoots (Bambusa balcooa) induced thyroid disruption - An in vitro study.

Endemic goitre and associated iodine deficiency disorders (IDDs) are a major concern in public health even in the period of post salt iodization in many regions. Among others the consumption of cyanogenic plants found responsible for the persistence of such diseases. Bamboo shoots (BS) is one such cyanogenic plant food that caused disruption of certain thyroid hormone synthesizing regulatory element as has already been reported in our earlier study. In this investigation the possible mechanism of thyrocytes disruption along with interruption of thyroid hormone biosynthesis by BS has been worked out. Commonly consumed BS, Bambusa Balcooa Roxb (BBR) water extract was analysed by GC MS; three doses below IC50 were administered to thyrocytes in culture with and without iodine. Expressions of thyroglobulin (Tg), pendrin (PDS) and monocarboxylate transporter 8 (MCT8) were evaluated in thyrocytes with cell cycle analysis, reactive oxygen species (ROS) generation, DNA oxidation and apoptotic regulation through Bax, Bcl-2 and p53. Phytochemical analysis of BBR extract revealed the presence of precursors and metabolic end products of cyanogenic glycosides. Dose dependent decrease in expression of Tg and PDS with concomitant decrease in gene expression of these with MCT8 were observed. Increased ROS, DNA oxidation and associated imbalance were found through increased Bax and p53 with decreased Bcl-2 that perturbed thyrocytes cell cycle. Cyanogenic constituents of BBR generates ROS associated oxidative changes in thyrocytes with DNA damage and oxidation and cell cycle disruption followed by inhibition of thyroid hormone synthesizing regulatory elements; addition of extra iodine showed partial prevention.

Fruit abortion of ‘Guifei’ mango (Mangifera indicaL.) affected biosynthesis of carotenoid and polyphenols in pulp

To investigate the effects of embryo abortion on fruit size and weight, fruit quality, chlorophyll, carotenoid, anthocyanin, flavonoid, and total polyphenols, the seeded fruit of mango (Mangifera indica L.) cultivar 'Guifei' were compared at the ripe stage. Seedless fruit had significantly smaller fruit size and lower fruit weight than seeded fruit in the cultivar. The experimental results suggested that embryo abortion at early stages of fruit ripening did not affect the concentration of total polyphenols in the pulp of matured fruit at green color or yellow color stages. However, the chlorophyll level decreased with ripening, lower in the abortion mango than in the normal mango. Carotenoid content increased throughout yellow stage and was significantly higher in the normal fruit compared to the abortion fruit. The concentrations of flavonoid were lower in the abortion fruit compared with normal fruit in the same color fruit. The expression of PSY and PDS was increased from green to yellow in abortion and normal mango. Expression of ANS and DFR was higher in the green color mango, in different development stages, and lower at the abortion stage in the yellow mango.

Thyroid-Specific Genes Expression Uncovered Age-Related Differences in Pediatric Thyroid Carcinomas.

Despite a more advanced stage of disease at presentation, a better response to radioiodine (RAI) therapy and a reduced overall mortality have been reported in pediatric differentiated thyroid cancer (DTC) in comparison to adult DTC. Few studies suggested that the better response to RAI therapy in pediatric patients might be associated with an increased expression of NIS. However, a marked heterogeneity within the pediatric group has been recognized. Children (<10 years old) usually present a more aggressive disease than adolescents (≥10–18 years old). By analyzing the expression of thyroid-specific genes in 38 sporadic pediatric tumors, we show that the expression of NIS, PDS, and TSHR was lower in children than adolescents (P < 0.05). A linear regression confirmed the association between NIS expression and age. Most significantly, NIS was expressed at similar levels in DTC from children and adults, whereas PDS and TSHR expression was even lower in DTC from children, compared to adolescents and adults. Our data suggest that biological behaviors of DTC in adolescents might differ from those in children and adults. Therefore, the premise that the expression of thyroid-specific genes is higher in tumors from pediatric patients than in adults is not entirely true and might be too oversimplified.

Isolation and characterization of the carotenoid biosynthetic genes LCYB, LCYE and CHXB from strawberry and their relation to carotenoid accumulation

Carotenoids are common pigments in yellow, orange and red fruits, and their compositions and contents are important indexes to evaluate the nutritional and commercial values of the fruits. To investigate the transcriptional regulation of carotenoid biosynthesis genes in relation to carotenoid accumulation during strawberry development, three cDNAs (LCYB, LCYE and CHXB) that encode carotenoid biosynthesis downstream enzymes (lycopene β-cyclase, lycopene ɛ-cyclase and β-ring hydroxylase) were isolated in the present study. Carotenoid accumulation and the expression of these genes along with three previously cloned upstream genes, PSY, PDS and ZDS, were analyzed. The data confirmed that the dominant carotenoids that accumulate in strawberries are lutein and β-carotene, and their contents varied with genotypes and decreased during fruit development. The expression analysis of carotenoid biosynthetic genes revealed that the pattern of upstream genes was opposite that of downstream genes. In contrast to the increased expression of PSY, PDS and ZDS, the decreased expression of LCYB, LCYE and CHXB correlated more closely with carotenoid accumulation in strawberries. Moreover, the expression profiles of LCYB and LCYE were consistent with the changes observed in β-carotene and lutein, respectively. These results suggested that the changes in genes expression related to carotenoid contents varied during strawberry development. In particular, LCYB and LCYE appeared to be the key regulatory genes for carotenoid accumulation in strawberries.

A non-climacteric fruit gene CaMADS-RIN regulates fruit ripening and ethylene biosynthesis in climacteric fruit.

MADS-box genes have been reported to play a major role in the molecular circuit of developmental regulation. Especially, SEPALLATA (SEP) group genes play a central role in the developmental regulation of ripening in both climacteric and non-climacteric fruits. However, the mechanisms underlying the regulation of SEP genes to non-climacteric fruits ripening are still unclear. Here a SEP gene of pepper, CaMADS-RIN, has been cloned and exhibited elevated expression at the onset of ripening of pepper. To further explore the function of CaMADS-RIN, an overexpressed construct was created and transformed into ripening inhibitor (rin) mutant tomato plants. Broad ripening phenotypes were observed in CaMADS-RIN overexpressed rin fruits. The accumulation of carotenoid and expression of PDS and ZDS were enhanced in overexpressed fruits compared with rin mutant. The transcripts of cell wall metabolism genes (PG, EXP1 and TBG4) and lipoxygenase genes (TomloxB and TomloxC) accumulated more abundant compared to rin mutant. Besides, both ethylene-dependent genes including ACS2, ACO1, E4 and E8 and ethylene-independent genes such as HDC and Nor were also up-regulated in transgenic fruits at different levels. Moreover, transgenic fruits showed approximately 1–3 times increase in ethylene production compared with rin mutant fruits. Yeast two-hybrid screen results indicated that CaMADS-RIN could interact with TAGL1, FUL1 and itself respectively as SlMADS-RIN did in vitro. These results suggest that CaMADS-RIN affects fruit ripening of tomato both in ethylene-dependent and ethylene-independent aspects, which will provide a set of significant data to explore the role of SEP genes in ripening of non-climacteric fruits.

Heterologous virus-induced gene silencing as a promising approach in plant functional genomics

VIGS (virus induced gene silencing) is considered as a powerful genomics tool for characterizing the function of genes in a few closely related plant species. The investigations have been carried out mainly in order to test if a pre-existing VIGS vector can serve as an efficient tool for gene silencing in a diverse array of plant species. Another route of investigation has been the constructing of new viral vectors to act in their hosts. Our approach was the creation of a heterologous system in which silencing of endogenous genes was achieved by sequences isolated from evolutionary remote species. In this study, we showed that a TRV-based vector cloned with sequences from a gymnosperm, Taxus baccata L. silenced the endogenous phytoene desaturase in an angiosperm, N. benthamiana. Our results showed that inserts of between 390 and 724bp isolated from a conserved fragment of the Taxus PDS led to silencing of its homolog in tobacco. The real time analysis indicated that the expression of PDS was reduced 2.1- to 4.0-fold in pTRV-TbPDS infected plants compared with buffer treated plants. Once the best insert is identified and the conditions are optimized for heterologous silencing by pTRV-TbPDS in tobacco, then we can test if TRV can serve as an efficient silencing vector in Taxus. This strategy could also be used to silence a diverse array of genes from a wide range of species which have no VIGS protocol. The results also showed that plants silenced heterologously by the VIGS system a minimally affected with respect to plant growth which may be ideal for studying the genes that their complete loss of function may lead to decrease of plant growth or plant death.

Expression of iodine metabolism genes in human thyroid tissues: evidence for age and BRAFV600E mutation dependency

Children present a higher susceptibility to developing thyroid cancer after radioiodine exposure and also a higher frequency of functional metastases than adults. To assess the mRNA expression of the sodium/iodide (Na(+)/I(-)) symporter (NIS), the Pendred syndrome gene (PDS), thyroperoxidase (TPO), thyroglobulin (Tg) and TSH receptor (TSH-R) in normal thyroid tissues (NTTs) and papillary thyroid carcinomas (PTCs) among different age groups. Analysis included 59 samples: 21 NTTs and 38 PTCs, of which 21 were the classic type (CPTC) and 17 the follicular variant (FVPTC). Patients were divided into three age groups: I (n = 16) 5-21 years, II (n = 13) 22-59 years, and III (n = 10) 60-91 years. The relative mRNA expression of the five target genes was determinate by quantitative reverse transcription polymerase chain reaction (QRT-PCR). Expression of all genes was significantly higher in NTTs than in PTCs, and it was not age dependent in the NTT group. Among PTCs, the mean expression of PDS, TPO and TSH-R was significantly lower in group II than in group I. PDS, TPO and Tg expression was significantly lower in classic PTCs than in FVPTCs. The difference was related to a higher frequency of the BRAF(V600E) mutation in the former group. The finding of higher PDS, TPO and TSH-R mRNA expression in paediatric vs. adult primary tumour tissues supports the hypothesis that this might contribute to the increased functional activity of metastases in the paediatric group. The finding that mRNA expression of the target genes in NTT was not age dependent does not provide an explanation for the higher susceptibility in the paediatric group.

Molecular mechanisms of epithelial cell-specific expression and regulation of the human anion exchanger (pendrin) gene

Pendrin, a Cl(-)/anion exchanger encoded by the gene PDS, is highly expressed in the kidney, thyroid, and inner ear epithelia and is essential for bicarbonate secretion, iodide accumulation, and endolymph ion balance, respectively. This study aimed to define promoter regulatory elements essential for renal, thyroid, and inner ear epithelial cell-specific expression of human PDS (hPDS) and to explore the effect of ambient pH and aldosterone on hPDS promoter activity. Endogenous pendrin mRNA and protein were detected in renal HEK293, thyroid LA2, and inner ear VOT36 epithelial cell lines, but not in the fibroblast cell line, NIH3T3. A 4.2-kb hPDS 5'-flanking DNA sequence and consecutive 5'-deletion products were cloned into luciferase reporter vectors and transiently transfected into the above cell lines. Distinct differences in expression/activity of deduced positive/negative regulatory elements within the hPDS promoter between HEK293, LA2, and VOT36 cells were demonstrated, with only basal activity in NIH3T3 cells. Acidic pH (7.0-7.1) decreased and alkaline pH (7.6-7.7) increased hPDS promoter activity in transfected HEK293 and VOT36, but not in LA2 cells. Aldosterone (10(-8) M) reduced hPDS promoter activity in HEK293 but had no effect in LA2 and VOT36 cells. These pH and aldosterone-induced effects on the hPDS promoter occurred within 96-bp and 89-bp regions, respectively, which likely contain distinct response elements to these modulators. Acidic pH and aldosterone decreased, and alkaline pH increased, endogenous pendrin mRNA level in HEK293 cells. In conclusion, pendrin-mediated HCO3(-) secretion in the renal tubule and anion transport in the endolymph may be regulated transcriptionally by systemic pH and aldosterone.

Differential regulation of apical and basal iodide transporters in the thyroid by thyroglobulin

We have shown that thyroglobulin (Tg) is a potent autocrine regulator of thyroid-specific gene expression, and proposed that the accumulated follicular Tg within the colloid is a major factor in determining follicular function. In the present report, we examined the effect of Tg on the action of TSH/cAMP and iodine with special focus on the regulation of basolateral and apical iodide transporters; the sodium/iodide symporter (NIS) and the pendred syndrome gene (PDS) by Tg. We show that expression of NIS and PDS are differentially regulated by Tg concentration and exposure time. In addition, we found that PDS gene was induced by TSH/cAMP and iodide in the presence of Tg. Based on these results, we propose a model for the physiological turnover of follicular function that is dynamically regulated by Tg.

Expression pattern of the pendrin and sodium/iodide symporter genes in human thyroid carcinoma cell lines and human thyroid tumors.

In the present study we analyzed the pattern of pendrin (PDS) and sodium/iodide symporter (NIS) gene expression in some thyroid carcinoma cell lines and a series of thyroid tumoral tissues. Total RNA was extracted from all cell lines and from 53 tissues, and gene expression was examined by RT-PCR. Semiquantitative 'multiplex' RT-PCR was used to assess variations in PDS gene expression among various thyroid pathologies. Pendrin expression was determined in the thyroid cell lines by Western blot analysis. PDS mRNA was expressed in all the cells investigated; conversely, NIS mRNA was detectable only in the B-CPAP cells. Pendrin protein was expressed in B-CPAP and WRO cell lines, reduced in FRO and absent in ARO cells. PDS gene expression was not detected in 5 of 25 differentiated thyroid carcinomas (DTC) while NIS gene was not expressed in six carcinomas. A concordance expression of both PDS and NIS transcripts was found in 20 DTC. In contrast, 2 neoplastic thyroid tissues carrying undetectable PDS mRNA maintained NIS transcript, and 3 thyroid carcinomas negative for NIS mRNA retained the expression of PDS gene. A semiquantitative analysis showed that the mean PDS mRNA levels were significantly decreased in DTC tissues. Our data demonstrate that pendrin expression: (i) is present in the more differentiated thyroid carcinoma cell lines studied; (ii) is reduced or absent in DTC tissues; (iii) may not correlate with the NIS expression. These alterations may contribute to the loss of iodine concentration ability detected in thyroid tumors.

Regulation of carotenoid biosynthesis during tomato development.

Phytoene synthase (Psy) and phytoene desaturase (Pds) are the first dedicated enzymes of the plant carotenoid biosynthesis pathway. We report here the organ-specific and temporal expression of PDS and PSY in tomato plants. Light increases the carotenoid content of seedlings but has little effect on PDS and PSY expression. Expression of both genes is induced in seedlings of the phytoene-accumulating mutant ghost and in wild-type seedlings treated with the Pds inhibitor norflurazon. Roots, which contain the lowest levels of carotenoids in the plant, have also the lowest levels of PDS and PSY expression. In flowers, expression of both genes and carotenoid content are higher in petals and anthers than in sepals and carpels. During flower development, expression of both PDS and PSY increases more than 10-fold immediately before anthesis. During fruit development, PSY expression increases more than 20-fold, but PDS expression increases less than threefold. We concluded that PSY and PDS are differentially regulated by stress and developmental mechanisms that control carotenoid biosynthesis in leaves, flowers, and fruits. We also report that PDS maps to chromosome 3, and thus it does not correspond to the GHOST locus, which maps to chromosome 11.