Identification and expression profiling of Pht1 phosphate transporters in wheat in controlled environments and in the field

Phosphorus (P) is an important macronutrient with critical functions in plants. Phosphate (Pi) transporters, which mediate Pi acquisition and Pi translocation within the plant, are key factors in Pi deficiency responses. However, their relevance for adaptation to long-term Pi limitation under agronomic conditions, particularly in wheat, remains unknown. Here, we describe the identification of the complete Pi transporter gene family (Pht1) in wheat (Triticum aestivum). Gene expression profiles were compared for hydroponic and field-grown plant tissues of wheat at multiple development stages. Cis-element analysis of selected Pht1 promoter regions was performed. A broad range of expression patterns of individual TaPht1 genes was observed in relation to tissue specificity and the nutrient supply in the soil or in liquid culture, as well as an influence of the experimental system. The expression patterns indicate the involvement of specific transporters in Pi uptake, and in Pi transport and remobilisation within the plant, at different growth developmental stages. Specifically, the influence of Pi nutrition indicates a complex regulatory pattern of TaPht1 gene transcript abundances as a response to low Pi availability in different culture systems, correlating with the existence of different cis-acting promoter elements.

Overexpression of a NAC transcription factor delays leaf senescence and increases grain nitrogen concentration in wheat

Increasing the duration of leaf photosynthesis during grain filling using slow-senescing functional stay-green phenotypes is a possible route for increasing grain yields in wheat (Triticum aestivum L.). However, delayed senescence may negatively affect nutrient remobilisation and hence reduce grain protein concentrations and grain quality. A novel NAC1-type transcription factor (hereafter TaNAC-S) was identified in wheat, with gene expression located primarily in leaf/sheath tissues, which decreased during post-anthesis leaf senescence. Expression of TaNAC-S in the second leaf correlated with delayed senescence in two doubled-haploid lines of an Avalon × Cadenza population (lines 112 and 181), which were distinct for leaf senescence. Transgenic wheat plants overexpressing TaNAC-S resulted in delayed leaf senescence (stay-green phenotype). Grain yield, aboveground biomass, harvest index and total grain N content were unaffected, but NAC over-expressing lines had higher grain N concentrations at similar grain yields compared to non-transgenic controls. These results indicate that TaNAC-S is a negative regulator of leaf senescence, and that delayed leaf senescence may lead not only to increased grain yields but also to increased grain protein concentrations.

Disposition of Erlotinib and Its Metabolite OSI420 in a Patient with High Bilirubin Levels

Erlotinib is an oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor approved for the treatment of non-small cell lung cancer and when combined with gemcitabine for pancreatic cancer. Dose reduction of erlotinib in patients with severe hepatic impairment has been established. We present the case of a male patient suffering from an adenocarcinoma of the pancreas with metastases in the liver and lung, whose disease progression led to highly elevated bilirubin levels of >14 mg/dl accompanied by icterus and pruritus. Despite the known contraindication, the patient agreed to be treated with 150 mg erlotinib p.o. per day. We performed therapeutic drug monitoring of erlotinib on day 1 after the first ingestion of erlotinib and then over a period of 19 days. One-compartment pharmacokinetics on day 1 were calculated, and, based on these data, a pharmacokinetic simulation for the following 19 days was run. On day 1 after the first erlotinib ingestion, plasma concentrations were identical to those described in the literature. On the following days, erlotinib plasma concentrations remained at a similar order of magnitude after daily ingestion. Compared with published data, OSI420 plasma concentrations were clearly higher from day 1 to 16. Due to disease progression, the last intake of erlotinib was on day 16, but plasma concentrations of the drug and metabolite increased excessively thereafter. The data give evidence that total bilirubin levels up to 14 mg/dl do not necessarily cause elevated plasma concentrations of erlotinib when given in doses of 150 mg per day.

Leaf developmental stage affects sulfate depletion and specific sulfate transporter expression during sulfur deprivation in Brassica napus L

BRASSICA NAPUS was grown under hydroponic conditions and responses to the removal of the external supply of sulfur (S) were analysed in roots and in leaves of different developmental age. The concentrations of sulfate and nitrate were greatest in the older leaves and least in younger leaves, whilst phosphate was greatest in roots and youngest leaves and least in old leaves. S-deprivation resulted in decreases in tissue sulfate concentrations at variable rates in the order: roots and young leaves > middle-aged leaves > oldest leaves. Phosphate concentrations were unaffected and nitrate concentrations were only depleted in the oldest leaves. Expression of representative members of the sulfate transporter gene family was assessed by Northern blotting in the respective tissues. Group 1 transporters (high affinity type) were induced in response to S-deprivation in all tissues except old leaves, where no expression was detected, and to the greatest extent in roots. Groups 2 and 5 (a BRASSICA Group 5 sulfate transporter is reported here, accession number: AJ311389) transporters showed either no or only a small induction by S-deprivation. Group 4 transporters (localised in the tonoplast membrane and thought to be involved in vacuolar sulfate efflux) were induced by S-deprivation with a complex pattern: 4;1 was expressed in root and mature leaves, was strongly induced by sulfur-deprivation in roots, and was also induced in the middle-aged leaves alone; 4;2 was only expressed under S-deprivation in parallel with the observed pattern of tissue sulfate concentrations. Expression patterns indicated that both differences in intracellular sulfate pools and localised aspects of the signal transduction pathway link tissue sulfate-status and sulfur-nutrition regulated gene expression.

The characteristic high sulfate content in Brassica oleracea is controlled by the expression and activity of sulfate transporters

The uptake and distribution of sulfate in BRASSICA OLERACEA, a species characterised by its high sulfate content in root and shoot, are coordinated and adjusted to the sulfur requirement for growth, even at external sulfate concentrations close to the K (m) value of the high-affinity sulfate transporters. Plants were able to grow normally and maintain a high sulfur content when grown at 5 or 10 microM sulfate in the root environment. Abundance of mRNAs for the high affinity sulfate transporters, BolSultr1;1 and BolSultr1;2, were enhanced at <or= 25 microM sulfate, and this was accompanied with an up to three-fold increase in the sulfate uptake capacity, whereas sulfate, organic sulfur, and thiol contents were only slightly affected. Upon sulfate deprivation, there was a much greater induction of the sulfate transporters, BolSultr1;1, BolSultr1;2, BolSultr1;3, BolSultr2;1, and BolSultr4;1, whilst the sulfate uptake capacity was only increased up to four-fold. Plant growth and shoot to root biomass allocation were affected only upon sulfate-deprivation and not at low external sulfate concentrations. From the current results it is suggested that the internal sulfate concentration may act as a determining factor in the regulation of activity and expression of sulfate transporters, and of shoot to root biomass allocation in B. OLERACEA.

Three-dimensional computer morphometry of the maxilla and face in infants with Pierre Robin sequence--a comparative study

OBJECTIVE

To analyze the morphology of the maxillary crest in infants with Pierre Robin sequence using an anthropometric coordinate system and to compare the data with those of healthy infants.

SETTING

The study was performed at a craniofacial center servicing a large geographic area.

PARTICIPANTS

The study involved eight infants aged 1-28 days (average, 7 days) with an established diagnosis of Pierre Robin sequence and six healthy infants aged 1-43 days (average, 22 days).

MAIN OUTCOME MEASURES

Physical models of the maxilla and face obtained by alginate replication were analyzed by computer morphometry yielding the three-dimensional topology of the maxillary crest.

RESULTS

The maxillary crest of children with Pierre Robin sequence shows an increased inclination relative to the transverse plane (30 +/- 3.9 degrees) as compared with that of healthy infants (20 +/- 2.9 degrees). The maxillary crest of the patients is shortened in the sagittal direction by comparison with healthy controls.

CONCLUSIONS

The increased inclination of the maxilla in infants with Pierre Robin sequence may aggravate the retroposition of the mandible and may thus be a pathogenetic factor contributing to the severe respiratory problems.

A MADS box transcription factor of the AP1/AGL9 subfamily is also expressed in the seed coat of pea (Pisum sativum) during development

As part of a programme to identify seed coat-specific transcripts in pea (Pisum sativum cv. Finale) using the differential display method, we identified and isolated a cDNA encoding a MADS box transcription factor. The predicted peptide contains 247 amino acids with the conserved N-terminal MADS box and is closely related to the AP1/AGL9 subfamily of the MADS box proteins. In addition to weak expression in petals, stamens and carpels, this MADS box mRNA is specifically expressed in the seed coat during seed development.

Three-dimensional analysis of cleft palate topology in newborn infants with reference to the cranial skeleton

OBJECTIVE

To describe a method of determining the three-dimensional topology of the palatal crest relative to a reproducible anthropomorphic coordinate system in newborn infants with unilateral cleft palate. For this purpose, physical models of the maxilla and face were analyzed by computer morphometry.

DESIGN

The study was limited to infants referred to the craniofacial center during the first 11 days after birth.

SETTING

The study was performed at a craniofacial center servicing a large geographic area.

PARTICIPANTS

The method was applied to 12 infants with unilateral cleft lip, alveolus, and palate (eight patients with left-side clefts and four with right-side clefts).

MAIN OUTCOME MEASURES

The three-dimensional topology of the palatal crest referenced to an anthropometric coordinate system was the primary outcome measure. The anthropometric reference system is defined by the tragus points and the midpoint of a line connecting the endocanthia.

RESULTS

The topology of the maxillary crests of the patients was characterized by considerable variability. The center of the premaxilla as defined by the attachment of the frenulum was frequently displaced by several millimeters from the midsagittal plane. The displacement was to the left in infants with right-side clefts and to the right in infants with left-side clefts. The premaxilla can be rotated by more than 30 degrees relative to the normal position. No significant retroposition of the minor segment as determined by the location of the tuber points was found. Several morphometric anomalies were found to be correlated linearly.

CONCLUSIONS

We propose that the morphologic deviations are in part caused by the neuromotor activity of the tongue and of the interrupted M. orbicularis oris. The data can serve as the starting point for a longitudinal study of craniofacial development in children with cleft palate and for studies on the efficacy of different therapeutic approaches.

Homodimers and heterodimers of Pho1-type phosphorylase isoforms in Solanum tuberosum L. as revealed by sequence-specific antibodies

Higher plants possess two types of glucan phosphorylase (EC 2.4.1.1). One isozyme type, designated as Pho1, is located in the plastid whereas the other type, Pho2, is restricted to the cytosol. For Solanum tuberosum L. two Pho1 type phosphorylases have been sequenced [Nakano, K. & Fukui, T. (1986) J. Biol. Chem. 261, 8230-8236; Sonnewald, U., Basner, A., Greve, B. & Steup, M. (1995) Plant Mol. Biol. 27, 567-576]. Both proteins (referred to as Pho1a and Pho1b, respectively) are highly similar (81-84% amino acid identity over most parts of the two sequences) with the exception of the N-terminal transit peptide and the large insertion located between the N- and the C-terminal domains. In this communication antibodies that bind specifically to either Pho1a or Pho1b were used to study both isoforms at the protein level. The antibodies were applied to both potato tuber and leaf extracts following either denaturing or non-denaturing electrophoresis. Pho1a but not Pho1b was immunochemically detectable in tuber extracts whereas leaf extracts contained both the Pho1a and Pho1b protein. During denaturing electrophoresis the two antigens comigrated. When the leaf Pho1 isoforms were separated by affinity electrophoresis three bands of activity were resolved; all of them were recognized by the anti-Pho1a antibodies, but only two of these reacted with the anti-Pho1b antibodies. The isoform binding exclusively to the anti-Pho1a antibodies comigrated with the Pho1 isozyme from potato tubers. Immunoprecipitation experiments performed with anti-Pho1a antibodies removed the entire Pho1 phosphorylase activity from both tuber and leaf extracts. Addition of anti-Pho1b antibodies to tuber extracts did not affect the enzyme pattern, whereas in leaf extracts one isoform remained unchanged but the two other bands were strongly retarded. This indicates that the Pho1a protein is present in all three forms and Pho1b is associated with Pho1a. Association of Pho1a and Pho1b was further demonstrated by cross-linking experiments using bis(sulfosuccinimidyl)suberate as linker. Immunoprecipitation experiments were also performed using extracts of transformed Escherichia coli cells that expressed either Pho1a or Pho1b or both simultaneously. Under these conditions a homodimeric Pho1b phosphorylase was observed that had a lower electrophoretic mobility than the heterodimer from leaves. In leaves of transgenic potato plants antisense inhibition of the Pho1a gene affected the formation of (Pho1a)2 more strongly than that of the heterodimer. Thus, in leaves, Pho1a exists both as a homodimer, (Pho1a)2 and as heterodimer, (Pho1a-Pho1b); a part of it appears to be covalently modified. Pho1b, in the homodimeric form, is often below the limit of detection. In tubers the homodimer, (Pho1a)2, is the only detectable Pho1-type enzyme. To our knowledge this is the first report on a heterodimeric structure of plant phosphorylase.

Sucrose metabolism during cotyledon development of Vicia faba L. is controlled by the concerted action of both sucrose-phosphate synthase and sucrose synthase: expression patterns, metabolic regulation and implications for seed development

The roles of sucrose-phosphate synthase (Sps) and sucrose synthase (Sus) in developing embryos of Vicia faba have been characterized. In the cotyledons the expression of both Sps and Sus is initiated in cells differentiating into storage tissue. This stage is characterized by a switch in the carbohydrate state from a high to a low hexoses to sucrose ratio. The carbohydrate state was found earlier to be controlled by seed coat-associated invertase. During cotyledon development the Sps-enzyme undergoes a cycle of deactivation and reactivation: the activated state is associated with the prestorage phase, desiccation and germination and the deactivated state with the storage phase. Sus activity is associated with the storage phase. Sps and Sus are differentially influenced by free sugars. Feeding hexoses to storage phase cotyledons increases levels of Sps-mRNA but not Sus-mRNA, Sps activity and Sps activation state and impairs storage functions evidenced by an increased sucrose to starch ratio and a downregulation of storage protein legumin B-mRNA. Sus enzyme activity is inhibited by free hexoses in vitro. It is proposed that the changing carbohydrate state during cotyledon development controls the ratio of Sps to Sus. Sps may have some significance for the initiation of the storage process possibly decreasing hexoses and/or increasing sucrose. The relevance of the changing carbohydrate state with respect to development and storage processes is discussed.

Glucan phosphorylases in Vicia faba L.: cloning, structural analysis and expression patterns of cytosolic and plastidic forms in relation to starch

We have isolated and characterised cDNA sequences from a Vicia faba cotyledonary library encoding a plastidic isoform (VfPho1) and a cytosolic isoform (VfPho2) of an alpha-1,4-glucan phosphorylase (EC 2.4.1.1; Commission on Plant Gene Nomenclature 1994). The Pho1 isoform is characterized by the presence of a plastidial transit peptide and an 81-residue stretch of additional amino acids in the middle of the polypeptide which are not found in the Pho2 isoform. We define the position of this so-called insertion sequence differently from previous authors. The Pho1 transcripts were found predominantly in the early seed coat and in cotyledons, and accumulated until the late desiccation phase, whereas Pho2 transcripts were about equally abundant in all investigated tissues. Activity patterns of both enzymes in cotyledons roughly followed mRNA accumulation patterns, with the exception of the late desiccation phases when mRNAs were degraded but enzyme activities remained at high level, even in long-stored seeds. The distinct Pho1 and Pho2 gene expression patterns in seed coats coincided with the transient accumulation pattern of starch. Similarly, in-situ hybridisation revealed a relationship between Pho1 gene expression and starch granule formation in developing cotyledons. Expression data and enzyme activity patterns were associated with starch formation during seed development, and could simply reflect a continuous accumulation of enzyme protein, ensuring immediate participation in starch degradation during germination.

Seed coat-associated invertases of fava bean control both unloading and storage functions: cloning of cDNAs and cell type-specific expression

We have studied the molecular physiology of photosynthate unloading and partitioning during seed development of fava bean (Vicia faba). During the prestorage phase, high levels of hexoses in the cotyledons and the apoplastic endospermal space are correlated with activity of cell wall-bound invertase in the seed coat. Three cDNAs were cloned. Sequence comparison revealed genes putatively encoding one soluble and two cell wall-bound isoforms of invertase. Expression was studied in different organs and tissues of developing seeds by RNA gel analysis, in situ hybridization, enzyme assay, and enzyme activity staining. One extracellular invertase gene is expressed during the prestorage phase in the thin-walled parenchyma of the seed coat, a region known to be the site of photoassimilate unloading. We propose a model for an invertase-mediated unloading process during early seed development and the regulation of cotyledonary sucrose metabolism. After unloading from the seed coat, sucrose is hydrolyzed by cell wall-bound invertases. Thus, invertase contributes to establish sink strength in young seeds. The resultant hexoses are loaded into the cotyledons and control carbohydrate partitioning via an influence on the sucrose synthase/sucrose-phosphate synthase pathway. The developmentally regulated degradation of the thin-walled parenchyma expressing the invertase apparently initiates the storage phase. This is characterized by a switch to a low sucrose/hexoses ratio. Feeding hexoses to storage-phase cotyledons in vitro increases the sucrose-phosphate synthase/sucrose synthase ratio and changes carbohydrate partitioning in favor of sucrose. Concomitantly, the transcript level of the major storage product legumin B is downregulated.