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[A 64-year-old woman with severe headache and progressive disturbance of consciousness].

We report a 64-year-old woman who developed nausea, headache, and consciousness disturbance. She was well until four years before the onset of her neurologic illness when (April of 1990 at her 59 years of the age) she was found to have an early cancer in her anterior wall of the lower stomach. Subtotal gastrectomy was performed and the operative result was reported as curative. Four years after the surgery (December of 1994 at her 64 years of the age), she noted suboccipital headache and nausea which had become progressively worse and she was admitted to our service on May 24, 1995. On admission, she appeared chronically ill but general physical examination was unremarkable with normal vital signs. Neurologically she was alert and not demented, and the higher cerebral functions were intact. Cranial nerves were also unremarkable. She was able to walk in tandem and on heels. No motor weakness or ataxia was noted. Deep tendon reflexes were moderately increased, however, no Babinski sign was noted. Although she had headache, no meningeal signs were seen. Slight superficial and vibratory sensory loss was noted in both feet. Routine blood work was again unremarkable except for slight increase in CEA to 8.3 ng/dl (N < 5 ng/dl). The opening pressure of lumbar CSF was 180 mm H2O and the CSF contained 39 cells/microliter, 79 mg of protein, and 10 mg/dl of glucose. Approximately half of the cells were atypical malignant cells. Plain CT was unremarkable, however, tentorial border showed enhancement after contrast infusion. FGS showed no malignant tumors in the stomach. She was treated with intravenous glycerol and whole brain radiation, however, she continued to complain of severe headache, and her sensorium started to be disturbed one month after the admission. Follow-up cranial CT scan revealed enlargement of the lateral and the third ventricles. Her consciousness progressively deteriorated and she became comatose three months after the admission. Repeated cranial CT scan showed enlargement of the ventricles, but no mass lesions were seen within the brain. She developed respiratory arrest on September 25 of the same year. She was discussed in a neurological CPC and the chief discussant arrived at the conclusion that the patient had a gastric cancer with meningeal seeding developing meningeal carcinomatosis. The cause of deep coma was ascribed to damage of cerebral cortical areas secondary to metastatic carcinoma cells and fibrinous materials in the surface of the brain. Postmortem examination revealed thickening and clouding of leptomeninges of the cerebral convexity. On histologic observation, patchy areas of fibrous thickening were seen in the cerebral leptomeninges; in such areas, adenocarcinomatous cells were seen scattered. The basal meninges were free of carcinoma cells, however, leptomeninges of the cerebellum and brain stem tegmentum contained scattered carcinoma cells. The lateral and the third ventricles were enlarged, however, insides of the brain were free of pathologies; the ependymal layer were intact. In the stomach no carcinoma cells were remaining. Pneumonic changes were seen in the right upper and the left lower lobes which appeared to be the direct cause of her death. No evidence of tentorial herniation was noted. The cause of her deep coma was not clearly determined, however, combination of hydrocephalus and cortical malfunction due to leptomeningeal carcinoma cell infiltration and fibrinous material accumulation appeared to have played a role.

Adenocarcinoma↗

Imbibition of Swietenia macrophylla (Meliaceae) seeds: the role of stomata.

BACKGROUND AND AIMS: The occurrence of stomata in seed coats is uncommon and there is limited information about their function(s). The aim of this study was to verify the distribution of stomata in seed coats of Swietenia macrophylla and to relate it to the imbibition process and aspects of the structure of the outer integument layers. METHODS: For the structural and ultrastructural studies, the seeds were processed using the usual techniques and studied under light and scanning electron microscopes. Histochemical tests were employed to identify the cell wall composition in the different seed coat portions. To assess the role of the stomata in the imbibition, non-impervious seeds were compared with partially impervious ones, in which only the embryo, median or hilar regions were left free. Further, the apoplastic pathway marker was employed to confirm the role of the stomata as sites of water passage during imbibition. KEY RESULTS: A positive relationship was observed between seed coat thickness and stomata density. The stomata were devoid of movement, with a large pore. They occurred in large numbers in the embryo region and extended with lower frequency towards the wing. Imbibition rates were related to stomata density, suggesting that the stomata act as preferential sites for water entry in the S. macrophylla seeds. CONCLUSIONS: At maturity, the stomata in the seed coat play a significant role in seed imbibition. The data may also infer that these permanently opened stomata have an important role in gas exchange during seed development, aiding embryo respiration.

Cell Wall↗

Three SAC1-like genes show overlapping patterns of expression in Arabidopsis but are remarkably silent during embryo development.

In Saccharomyces cerevisiae, the SAC1 gene encodes a polyphosphoinositide phosphatase (PPIPase) that modulates the levels of phosphoinositides, which are key regulators of a number of signal transduction processes. SAC1p has been implicated in multiple cellular functions: actin cytoskeleton organization, secretory functions, inositol metabolism, ATP transport, and multiple-drug sensitivity. Here, we describe the characterization of three genes in Arabidopsis thaliana, AtSAC1a, AtSAC1b, and AtSAC1c, encoding proteins similar to those of yeast SAC1p. We demonstrated that the three AtSAC1 proteins are functional homologs of the yeast SAC1p because they can rescue the cold-sensitive and inositol auxotroph yeast sac1-null mutant strain. The fact that Arabidopsis and yeast SAC1 genes derived from a common ancestor suggests that this plant multigenic family is involved in the phosphoinositide pathway and in a range of cellular functions similar to those in yeast. Using GFP fusion experiments, we demonstrate that the three AtSAC1 proteins are targeted to the endoplasmic reticulum. Their expression patterns are overlapping, with at least two members expressed in each organ. Remarkably, AtSAC1 genes are not expressed during seed development, and therefore additional phosphatases are required to control phosphoinositide levels in seeds.

Amino Acid Sequence↗

Expression of antiapoptotic genes bcl-xL and ced-9 in tomato enhances tolerance to viral-induced necrosis and abiotic stress.

D satellite RNA (satRNA) is a strain of cucumber mosaic virus (CMV) satRNA that induces an epidemic lethal disease in tomato. No natural resistance or tolerance has ever been found. Previously, we demonstrated the involvement of programmed cell death in disease development. Here, transgenic tomato plants expressing animal antiapoptotic genes bcl-xL and ced-9 were generated through agrobacterium-mediated transformation. High expression of bcl-xL or ced-9 affected plant growth and seed development. Inoculation of seedlings with CMV/D satRNA at T(1) and T(2) generations resulted in delayed cell-death symptoms or absence of symptoms. The degree of symptom suppression was correlated with increasing expression levels of the transgenes. Survival rates were compared among inoculated transgenic lines expressing bcl-xL, ced-9, and bcl-xL (G138A), a loss-of-function mutant of bcl-xL. More than 80% of the bcl-xL and ced-9 T(1) transgenic lines showed higher survival rates than the average for bcl-xL (G138A) transgenic lines. Total RNA extracted from surviving plants contained D satRNA, indicating systemic accumulation of D satRNA. Thus, expression of bcl-xL and ced-9 improved tolerance to, rather than resistance to, CMV/D satRNA infection. In addition, expression of bcl-xL and ced-9 specifically abrogated the formation of necrotic lesions, but not other symptoms, in tomato leaves during chilling at 4 degrees C. At 7 degrees C, temperature-induced leaf senescence was dramatically delayed in bcl-xL and ced-9 transgenic plants, and high levels of anthocyanins accumulated, possibly limiting oxidative stress. Hence, expression of these animal antiapoptotic genes improved plant survival under abiotic or biotic stress.

Agrobacterium tumefaciens↗

The developmental expression of the maize regulatory gene Hopi determines germination-dependent anthocyanin accumulation.

The Hopi gene is a member of the maize r1 gene family. By genetic and molecular analyses we report that Hopi consists of a single gene residing on chromosome 10 approximately 4.5 cM distal to r1. Hopi conditions anthocyanin deposition in aleurone, scutellum, pericarp, root, mesocotyl, leaves, and anthers, thus representing one of the broadest specifications of pigmentation pattern reported to date of all the r1 genes. A unique feature of the Hopi gene is that seeds are completely devoid of pigment at maturity but show a photoinducible germination-dependent anthocyanin accumulation in aleurone and scutellum. Our analysis has shown that the Hopi transcript is not present in scutellum of developing seeds but is induced only upon germination and that the simultaneous presence of both C1 and Hopi mRNAs is necessary to achieve A1 activation in scutella. We conclude that the expression pattern of the Hopi gene accounts for the germination-dependent anthocyanin synthesis in scutella, whereas the developmental competence of germinating seeds to induce anthocyanin production in scutella results from the combination of the light-inducible expression of C1 and the developmentally regulated expression of the Hopi gene.

Alcohol Oxidoreductases↗

Tall tales from sly dwarves: novel functions of gibberellins in plant development.

Gibberellins (GAs) are endogenous hormones controlling numerous aspects of plant growth and development. Our present understanding of GA physiology is based largely on genetic analysis in model plants such as Arabidopsis. In spite of the success of this approach, the discovery of additional physiological roles for GAs in seed development, pollen tube growth and meristem development indicates that the existing collection of GA-related mutants (identified partially or entirely on the basis of vegetative phenotypes) has failed to uncover all aspects of plant development that are controlled by GAs. The continued use of ever improving forward and reverse genetic techniques is expected to lead to the discovery of further novel roles for GAs in plant development.

Arabidopsis↗

Seeds for a better future: 'low phytate' grains help to overcome malnutrition and reduce pollution.

myo-Inositol(1,2,3,4,5,6)hexakisphosphate (InsP(6) or 'phytic acid') was first known as the storage form of phosphorus in seeds. Seed-derived dietary InsP(6) can contribute to iron and zinc deficiency in human populations. Excretion of 'phytic acid phosphorus' by non-ruminants such as poultry, swine and fish can contribute to water pollution. Sustainable solutions to these important problems might depend on progress in the molecular biology and genetics of InsP(6) accumulation during seed development. The development of 'low phytate' grain and legume genotypes could help advance our understanding of this biology, and when used in foods and feeds might help to reduce human malnutrition and reduce animal waste phosphorus.

Aged↗

Evidence for ovarian self-incompatibility as a cause of self-sterility in the relictual woody angiosperm, Pseudowintera axillaris (Winteraceae).

Species within the genus Pseudowintera exhibit high rates of self-sterility. Self-sterility in the genus has been previously posited-but not confirmed-to be the result of late-acting ovarian self-incompatibility (OSI) functioning within nucellar tissue of the ovule to prevent self pollen tubes from entering the embryo sac. Structural and functional aspects of pollen-carpel interactions and early seed development following cross- and self-pollination were investigated in P. axillaris to determine the site, timing and possible mechanisms of self-sterility. No significant differences were observed between pollen tube growth, ovule penetration and double fertilization following cross- and self-pollination. Pollen tubes exhibited phasic growth in an extracellular matrix composed of proteins and carbohydrates, as well as arabinogalactans/arabinogalactan proteins. A uniform failure in embryo sac development prior to division of the zygote was apparent within 15 d following double fertilization by self gametes. Results indicate that SI mechanisms in P. axillaris do not prevent double fertilization from occurring. Instead, mechanisms of self-sterility affect post-zygotic development of the embryo sac. Although self-sterility may be attributed to inbreeding depression, given the post-zygotic nature of failure in embryo sac development, the possibility of late-acting OSI is discussed.

Crosses, Genetic↗

The MIP family of integral membrane channel proteins: sequence comparisons, evolutionary relationships, reconstructed pathway of evolution, and proposed functional differentiation of the two repeated halves of the proteins.

The major intrinsic protein (MIP) of the bovine lens fiber cell membrane was the first member of the MIP family of proteins to be sequenced and characterized. It is probably a homotetramer with transmembrane channel activity that plays a role in lens biogenesis or maintenance. The polypeptide chain of each subunit may span the membrane six times, and both the N- and C-termini face the cell cytoplasm. Eighteen sequenced or partially sequenced proteins from bacteria, yeast, plants, and animals have now been shown to be members of the MIP family. These proteins appear to function in (1) metazoan development and neurogenesis (MIP and BIB), (2) water transport across the human erythrocyte membrane (ChIP), (3) communication between host plant cells and symbiotic nitrogen-fixing bacteria (NOD), (4) transport across the tonoplast membrane during plant seed development (alpha-TIP), (5) water stress-induced resistance to desiccation in plants (Wsi-TIP), (6) suppression of a genetic growth defect on fermentable sugars in yeast (FPS1), and (7) transport of glycerol across bacterial cell membranes (GlpF). One other sequenced member of the MIP family (ORF1 of Lactococcus lactis) has no known physiological function. The biochemical functions of the eukaryotic proteins are not well established. Computer analyses have revealed that the first and second halves of all MIP family proteins probably arose by a tandem, intragenic, duplication event. Thus, the primary structure of putative transmembrane helices 1 to 3 is similar to that of putative transmembrane helices 4 to 6 even though they are of opposite orientation in the membrane. Among the most conserved residues in these two repeated halves are a membrane-embedded glutamate (E) in helices 1 and 4, an asparagine-proline-alanine (NPA) sequence in the loops between helices 2 and 3 (cytoplasmically localized) and helices 5 and 6 (extracellularly localized), and a glycine within helices 3 and 6. Statistical analyses suggest that the two halves of these proteins have evolved to serve distinct functions: the first half is more important for the generalized or common functions of these proteins, while the second half of these proteins is more differentiated to provide specific or dissimilar functions of the proteins. The apparent origin of MIP family proteins by duplication of a three-spanner precursor protein suggests an evolutionary origin distinct from other transport proteins with six transmembrane spanners.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

Imprinting in the endosperm: a possible role in preventing wide hybridization.

Reproductive isolation is considered to play a key part in evolution, and plants and animals have developed a range of strategies that minimize gene flow between species. In plants, these strategies involve either pre-zygotic barriers, such as differences in floral structure and pollen-stigma recognition, or post-zygotic barriers, which are less well understood and affect aspects of seed development ranging from fertilization to maturation. In most angiosperms, a double fertilization event gives rise to a zygote and the endosperm: a triploid tissue with an unequal parental genomic contribution, which, like the placenta of mammals, provides reserves to the developing embryo. Interestingly, many aspects of endosperm development, again like the placenta, are regulated by a range of epigenetic mechanisms that are globally termed imprinting. Imprinted genes are characterized by their uniparental expression, the other parental allele being silenced. Normal development of the endosperm thus requires a highly specific balance of gene expression, from either the maternal or paternal genomes. Any alteration of this balance resulting from changes in allelic copy number, sequence or epigenetic imprints can cause endosperm failure and eventual seed abortion. In its widest sense, the endosperm thus serves as an accurate 'sensor' of compatibility between parents. A first step in understanding this important, yet complex system must clearly be the isolation and characterization of as wide a range as possible of imprinted genes.

Crosses, Genetic↗

Investigations into seed dormancy in Grevillea linearifolia, G. buxifolia and G. sericea: anatomy and histochemistry of the seed coat.

BACKGROUND AND AIMS: Seeds of east Australian Grevillea species generally recruit post-fire; previous work showed that the seed coat was the controller of dormancy in Grevillea linearifolia. Former studies on seed development in Grevillea have concentrated on embryology, with little information that would allow testing of hypotheses about the breaking of dormancy by fire-related cues. Our aim was to investigate structural and chemical characteristics of the seed coat that may be related to dormancy for three Grevillea species. METHODS: Seeds of Grevillea linearifolia, Grevillea buxifolia and Grevillea sericea were investigated using gross dissection, thin sectioning and histochemical staining. Water movement across the seed coat was tested for by determining the water content of embryos from imbibed and dry seeds of G. sericea. Penetration of intact seeds by Lucifer Yellow was used to test for internal barriers to diffusion of high-molecular-weight compounds. KEY RESULTS: Two integuments were present in the seed coat: an outer testa, with exo-, meso- and endotestal (palisade) layers, and an inner tegmen of unlignified sclerenchyma. A hypostase at the chalazal end was a region of structural difference in the seed coat, and differed slightly among the three species. An internal cuticle was found on each side of the sclerenchyma layer. The embryos of imbibed seeds had a water content six times that of dry seeds. Barriers to diffusion of Lucifer Yellow existed at the exotestal and the endotestal/hypostase layers. CONCLUSIONS: Several potential mechanisms of seed coat dormancy were identified. The embryo appeared to be completely surrounded by outer and inner barriers to diffusion of high-molecular-weight compounds. Phenolic compounds present in the exotesta could interfere with gas exchange. The sclerenchyma layer, together with strengthening in the endotestal and exotestal cells, could act as a mechanical constraint.

Germination↗

Post-termination-induced and hormonally dependent expression of low-molecular-weight heat shock protein genes in Douglas fir.

We have isolated and sequenced two cDNA clones (PM 18.2A; PM 18.2B) from Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) which encode for the low-molecular-weight heat shock proteins (LMW HSPs) of 18.2 kDa. The predicted amino acid sequences of the two Douglas fir proteins are 97.5% identical. A phylogenetic tree of class I LMW HSPs showed that the PM LMW HSPs are found within a subgroup consisting exclusively of dicot species indicating that class I LMW HSPs evolved from a common ancestor predating the divergence of gymnosperms and angiosperms. Northern blots of RNA from dry, imbibed, stratified and germinated seeds revealed a notable induction of LMW HSP transcripts during post-germination and early seedling growth. Unlike previous reports, the expression of these HSPs appears to be primarily restricted to seedlings as mRNA transcripts were detected at very low levels during seed development and desiccation. Maximum induction of LMW HSPs in seedlings occurred during heat shock treatment at 38-40 degrees C, whereas cold shock or wounding failed to induce HSP transcripts. The transcription of HSP genes is up regulated by GA, MeJA and auxin and is down regulated by ABA. Methyl jasmonate treatment induced expression of these genes in dormant seeds of Douglas fir. The expression of class I cytoplasmic LMW HSPs in seedlings and their regulation by plant growth regulators suggests specific roles in plant development other than desiccation tolerance.

Amino Acid Sequence↗

Characterization of proteins released from legume seeds in hot water.

When immersed in water at 50-60 degrees, mature soybean seeds release a large amount of protein. The major protein released was basic 7S globulin (Bg), which is present in the cotyledons of soybean seeds. The released Bg consisted of the 27,000 and 16,000 subunits which were linked by disulphide bonding and glycosylated. The released Bg exhibited an identical structure with the mature Bg which was synthesized in the normal developing seeds. Proteins like Bg were also found to be released into hot water from the seeds of legume species such as azuki-bean, cowpea, mung-bean and winged-bean. Besides Bg and Bg-like proteins, a few proteins including the 9,000 hydrophobic protein in soybean, ubiquitin in cowpea and mung-bean, and Kunitz trypsin inhibitor in winged-bean, were released from the seeds in hot water.

Amino Acid Sequence↗

rha1, a gene encoding a small GTP binding protein from Arabidopsis, is expressed primarily in developing guard cells.

The rha1 gene from Arabidopsis encodes a small GTP binding protein belonging to the Ypt/Rab family. Transgenic Arabidopsis plants containing the promoter region of the rha1 gene fused to the beta-glucuronidase (gus) reporter gene revealed gus expression limited mainly to the guard cells of stomata, the stipules, and the root tip of young plants. In flowering plants, expression was found predominantly in the receptacle and in guard cells of the different flower organs. High GUS activity could also be seen in callus tissue and developing seeds. No detectable activity was present in other plant tissues; activity could not be induced by various treatments. GUS activity was visualized histochemically using both 5-bromo-4-chloro-3-indolyl beta-D-glucuronide and a newly developed GUS substrate: Sudan II-beta-glucuronide. The latter precipitates as red crystals at the site of GUS activity. Results obtained by the gus analysis were confirmed by whole-mount mRNA in situ hybridization. A hypothesis for the function of the Rha1 protein is discussed.

Amino Acid Sequence↗

Evaluation of the new cesium-131 seed for use in low-energy x-ray brachytherapy.

Characterization measurements and calculations were performed on a new medical seed developed by IsoRay Inc. in Richland, Washington, that utilizes the short-lived isotope 131Cs. This model has recently received FDA 510(k) clearance. The objective of this work was to characterize the dosimetric properties of the new seed according to the AAPM Task Group 43 recommendations. Cesium-131 is a low-energy x-ray emitter, with the most prominent peaks in the 29 keV to 34 keV region. The intended application is brachytherapy for treating cancers in prostate, breast, head and neck, lung, and pancreas. The evaluations performed included air-kerma strength, radial dose function, anisotropy in phantom, half-life, energy spectra, and internal activity. The results indicate the CS-1 seeds have a dose-rate constant of 0.915 cGy hr(-1) U(-1) in water, dose penetration characteristics similar to 125I and 103Pd, anisotropy function values on the order of 0.71 at short distances and small angles, and an average anisotropy factor of 0.964. The overall dosimetric characteristics are similar to 125I and 103Pd seeds with the exception of half-life, which is 9.7 days, as compared to 17 days for 103Pd and 60 days for 125I. The shorter half-life may offer significant advantages in biological effectiveness.

Air↗

Cloning and expression of five myb-related genes from rice seed.

Three elements in the promoter of rice glutelin genes are important for their endosperm specific expression. One of these, an AACA motif, has been shown to be a negative regulator in non-seed tissues and has a similarity to the barley gibberellin responsive element recognized by MYB-like DNA binding proteins. A cDNA library constructed from immature rice seed was screened using two types of myb gene probes to isolate cDNA clones representing genes encoding MYB-like DNA binding proteins that may recognize the AACA motif in rice glutelin gene promoter. We obtained four cDNA clones encoding MYB-related proteins, Oryza sativa MYB (OSMYB) 1-4, using the maize C1 probe. Another myb-like clone, Osmyb5, was obtained by screening a rice seed cDNA library with probes designed to recognize the AACA-like binding domain in GAMYB and PHMYB3. RT-PCR was used to analyze Osmyb expression during rice seed development and their presence in other rice tissues, as it was not possible to detect these mRNAs by conventional Northern analysis. RT-PCR analysis showed that Osmyb2, Osmyb3 and Osmyb5 genes were expressed in all tissues examined. In seed, the mRNA levels of Osmyb1 and Osmyb4 genes reached a maximum at 14 days after flowering (DAF), suggesting that these genes may play a role in seed maturation. As Osmyb5 exhibits a high similarity to the regions in both GAMYB and PHMYB3, which can bind to the AACA motif, there is a possibility that the OSMYB5 protein may bind to the AACA motif of glutelin genes.

Amino Acid Sequence↗

Stem infusions enhanced methionine content of soybean storage protein.

The quality of soybean (Glycine max [L.] Merrill) seed storage protein is limited by its low methionine (Met) content. Met supplementation of an in vitro soybean cotyledon culture has been shown to increase Met content by 21.9% due to an inhibition of the synthesis of the Met-devoid beta subunit of 7S storage protein (JF Thompson et al. 1981, Phytochemistry 20: 941-945). The objective of this research was to determine if Met supplementation of intact plants would result in a similar improvement in soybean protein quality. A solution including 10 millimolar d,l malic acid plus 10 millimolar K(2)HPO(4) with or without 20 millimolar d,l Met or 20 millimolar Na(2)SO(4) was infused throughout seed development into lower stem internodes of soybeans (cv ;Williams 79' or ;Williams 82') grown under both greenhouse and field conditions. Pediatric intravenous kits were used to infuse an average of 51.2 milliliters per plant. Met content of whole soybean seeds from intact plants receiving Met infusions increased by as much as 22.7%. Even greater (up to 31.0%) increases in cysteine (Cys) content were noted, indicating that soybean plants are able to metabolize Met to Cys, or that supplemental Met allows Cys accumulation by some other mechanism. Electrophoretic patterns showed a dramatic decrease in the synthesis of the beta subunit of 7S storage protein when Met was supplemented, and this effect was not confined to seeds at the lower nodes. In addition, seeds from upper compared to lower plant nodes (regardless of infusion treatment) had greater protein content (45.0 versus 41.6 w/w%), and different protein composition, as indicated by significantly different amino acid profiles. Methionine supplementation of intact soybean plants improved protein quality through an alteration in storage protein composition.

Journal Article↗

A plasma membrane H+-ATPase is required for the formation of proanthocyanidins in the seed coat endothelium of Arabidopsis thaliana.

The plasma membrane in plant cells is energized with an electrical potential and proton gradient generated through the action of H+ pumps belonging to the P-type ATPase superfamily. The Arabidopsis genome encodes 11 plasma membrane H+ pumps. Auto-inhibited H+-ATPase isoform 10 (AHA10) is expressed primarily in developing seeds. Here we show that four independent gene disruptions of AHA10 result in seed coats with a transparent testa (tt) phenotype (light-colored seeds). A quantitative analysis of extractable flavonoids in aha10 seeds revealed an approximately 100-fold reduction of proanthocyanidin (PA), one of the two major end-product pigments in the flavonoid biosynthetic pathway. In wild-type seed coat endothelial cells, PA accumulates in a large central vacuole. In aha10 mutants, the formation of this vacuole is impaired, as indicated by the predominance of multiple small vacuoles observed by fluorescence microscopy using a vacuole-specific dye, 5-(and -6)-carboxy 2',7'-dichlorofluorescein diacetate. A similar vacuolar defect was also observed for another tt mutant, tt12, a proton-coupled multidrug and toxic compound extrusion transporter potentially involved in loading provacuoles with a flavonoid intermediate required for PA production. The endothelial cells in aha10 mutants are otherwise healthy, as indicated by the lack of a significant decrease in (i) the accumulation of other flavonoid pathway end products, such as anthocyanins, and (ii) mRNA levels for two endothelium-specific transcripts (TT12 and BAN). Thus, the specific effect of aha10 on vacuolar and PA biogenesis provides genetic evidence to support an unexpected endomembrane function for a member of the plasma membrane H+-ATPase family.

Anthocyanins↗