ADP-glucose Pyrophosphorylase Large Subunit Research Articles

Two negative cis-regulatory regions involved in fruit-specific promoter activity from watermelon (Citrullus vulgaris S.)

A 1.8 kb 5′-flanking region of the large subunit of ADP-glucose pyrophosphorylase, isolated from watermelon (Citrullus vulgaris S.), has fruit-specific promoter activity in transgenic tomato plants. Two negative regulatory regions, from –986 to –959 and from –472 to –424, were identified in this promoter region by fine deletion analyses. Removal of both regions led to constitutive expression in epidermal cells. Gain-of-function experiments showed that these two regions were sufficient to inhibit RFP (red fluorescent protein) expression in transformed epidermal cells when fused to the cauliflower mosaic virus (CaMV) 35S minimal promoter. Gel mobility shift experiments demonstrated the presence of leaf nuclear factors that interact with these two elements. A TCCAAAA motif was identified in these two regions, as well as one in the reverse orientation, which was confirmed to be a novel specific cis-element. A quantitative β-glucuronidase (GUS) activity assay of stable transgenic tomato plants showed that the activities of chimeric promoters harbouring only one of the two cis-elements, or both, were ∼10-fold higher in fruits than in leaves. These data confirm that the TCCAAAA motif functions as a fruit-specific element by inhibiting gene expression in leaves.

Molecular regulation of sink–source transition in rice leaf sheaths during the heading period

The upper leaf sheath of rice (Oryza sativa L.) serves as a temporary starch sink before heading, subsequently becoming a carbon source tissue to the growing panicle at the post-heading stage. The time of sink–source transition in upper leaf sheaths is highly correlated to the panicle exsertion. Here, we found that the expression profiles of starch synthesis genes such as ADP-glucose pyrophosphorylase large subunit 2, granule-bound starch synthase II, soluble starch synthase I, starch branching enzyme (SBE) I, SBEIII, and SBEIV were highly correlated with starch content changes during the heading period in the second leaf sheath below the flag leaf. In addition, the α-amylase2A and β-amylase were considered as major genes that were in charge of starch degradation at the post-heading period. Of the five sucrose transporter (OsSUT) genes, OsSUT1 and OsSUT4 appeared to play an important role in sucrose loading into the phloem of source leaf sheaths. Moreover, the microarray-based data implied that the dominant processes associated with functional leaf sheath transition from sink to source were carbohydrate metabolism and the translocation of the carbon and nitrogen sources and inorganic phosphate.

Direct Appraisal of the Potato Tuber ADP-glucose Pyrophosphorylase Large Subunit in Enzyme Function by Study of a Novel Mutant Form

The higher plant ADP-glucose pyrophosphorylase is a heterotetramer consisting of two subunit types, which have evolved at different rates from a common ancestral gene. The potato tuber small subunit (SS) displays both catalytic and regulatory properties, whereas the exact role of the large subunit (LS), which contains substrate and effector binding sites, remains unresolved. We identified a mutation, S302N, which increased the solubility of the recombinant potato tuber LS and, in turn, enabling it to form a homotetrameric structure. The LS302N homotetramer possesses very little enzyme activity at a level 100-fold less than that seen for the unactivated SS homotetramer. Unlike the SS enzyme, however, the LS302N homotetramer enzyme is neither activated by the effector 3-phosphoglycerate nor inhibited by P(i). When combined with the catalytically silenced SS, S D143N, however, the LS302N-containing enzyme shows significantly enhanced catalytic activity and restored 3-PGA activation. This unmasking of catalytic and regulatory potential of the LS is conspicuously evident when the activities of the resurrected L(K41R.T51K.S302N) homotetramer are compared with its heterotetrameric form assembled with S D143N. Overall, these results indicate that the LS possesses catalytic and regulatory properties only when assembled with SS and that the net properties of the heterotetrameric enzyme is a product of subunit synergy.

Catalytic implications of the higher plant ADP-glucose pyrophosphorylase large subunit

ADP-glucose pyrophosphorylase, a key regulatory enzyme of starch biosynthesis, is composed of a pair of catalytic small subunits (SSs) and a pair of catalytically disabled large subunits (LSs). The N-terminal region of the LS has been known to be essential for the allosteric regulatory properties of the heterotetrameric enzyme. To gain further insight on the role of this region and the LS itself in enzyme function, the six proline residues found in the N-terminal region of the potato tuber AGPase were subjected to scanning mutagenesis. The wildtype and various mutant heterotetramers were expressed using our newly developed host-vector system, purified, and their kinetic parameters assessed. While P 17L, P 26L, and P 55L mutations only moderately affected the kinetic properties, P 52L and P 66L gave rise to significant and contrasting changes in allosteric properties: P 66L enzyme displayed up-regulatory properties toward 3-PGA while the P 52L enzyme had down-regulatory properties. Unlike the other mutants, however, various mutations at P 44 led to only moderate changes in regulatory properties, but had severely impaired catalytic rates, apparent substrate affinities, and responsiveness to metabolic effectors, indicating Pro-44 or the LS is essential for optimal catalysis and activation of the AGPase heterotetramer. The catalytic importance of the LS is further supported by photoaffinity labeling studies, which revealed that the LS binds ATP at the same efficiency as the SS. These results indicate that the LS, although considered having no catalytic activity, may mimic many of the catalytic events undertaken by the SS and, thereby, influences net catalysis of the heterotetrameric enzyme.

A mutant of rice lacking the leaf large subunit of ADP-glucose pyrophosphorylase has drastically reduced leaf starch content but grows normally.

A mutant of rice was identified with a Tos17 insertion in OsAPL1, a gene encoding a large subunit (LSU) of ADP-glucose pyrophosphorylase (AGPase). The insertion prevents production of a normal transcript from OsAPL1. Characterisation of the mutant (apl1) showed that the LSU encoded by OsAPL1 is required for AGPase activity in rice leaf blades. In mutant leaf blades, the AGPase small subunit protein is not detectable and the AGPase activity and starch content are reduced to <1 and <5% of that in wild type blades, respectively. The mutation also leads to a reduction in starch content in the leaf sheaths but does not significantly affect AGPase activity or starch synthesis in other parts of the plant. The sucrose, glucose and fructose contents of the leaves are not affected by the mutation. Despite the near absence of starch in the leaf blades, apl1 mutant rice plants grow and develop normally under controlled environmental conditions and show no reduction in productivity.

Field Evaluation of Transgenic Wheat Expressing a Modified ADP‐Glucose Pyrophosphorylase Large Subunit

ABSTRACTWheat yield is influenced by the efficacy of seed starch biosynthetic enzymes. ADP‐glucose pyrophosphorylase (AGP) catalyzes a rate‐limiting step in seed starch biosynthesis. We transformed the hard spring wheat (Triticum aestivum L.) cultivar Hi‐Line with a modified maize AGP large subunit sequence (Sh2r6hs) to increase AGP activity. In previously described growth chamber studies, Sh2r6hs conditioned increased AGP activity, seed yield, and plant size. The primary objective of this study was to determine whether a similar yield enhancement could be detected under field conditions. Sh2r6hs transgenics were field tested over four growing years, in three locations, with varying planting density and irrigation. The results indicate that significant yield increases were more likely to occur in space‐planted, irrigated environments than densely planted, rainfed environments, suggesting that limited abiotic resources may subsequently limit Sh2r6hs‐associated yield enhancement. In elite lines, as in the F2–derived trials in which tissue culture derived mutations were reduced by out‐crossing, Sh2r6hs appears to confer a yield advantage only when field conditions are nonlimiting.

ATP binding site in the plant ADP-glucose pyrophosphorylase large subunit

The ATP binding region in the catalytically inactive large subunit (LS) of the potato tuber ADP-glucose pyrophosphorylase was identified and investigated. Mutations at the ATP binding significantly affected not only the apparent affinities for ATP and Glc-1-P, and catalytic rate but also in many instances, sensitivity to 3-phosphoglycerate. The catalytic rates of the LS mutant enzymes correlated most strongly with changes in the affinity toward ATP, a relationship substantiated by photoaffinity labeling studies with azido-ATP analog. These results indicate that the LS, although catalytically defective, interacts cooperatively with the catalytic small subunit in binding substrates and effectors and, in turn, influencing net catalysis.

Expression of a modified ADP-glucose pyrophosphorylase large subunit in wheat seeds stimulates photosynthesis and carbon metabolism

ADP-glucose pyrophosphorylase (AGP) is the rate-limiting step in seed starch biosynthesis. Expression of an altered maize AGP large subunit (Sh2r6hs) in wheat (Triticum aestivum L.) results in increased AGP activity in developing seed endosperm and seed yield. The yield phenotype involves increases in both seed number and total plant biomass. Here we describe stimulation of photosynthesis by the seed-specific Sh2r6hs transgene. Photosynthetic rates were increased in Sh2r6hs-expressing plants under high light but not low light growth conditions, peaking at roughly 7 days after flowering (DAF). In addition, there were significant increases in levels of fructose, glucose, and sucrose in flag leaves at both 7 and 14 DAF. In seeds, levels of carbon metabolites at 7 and 14 DAF were relatively unchanged but increases in glucose, ADP-glucose, and UDP-glucose were observed in seeds from Sh2r6hs positive plants at maturity. Increased photosynthetic rates relatively early in seed development appear to be key to the Sh2r6hs enhanced yield phenotype as no yield increase or photosynthetic rate changes were found when plants were grown in a suboptimal light environment. These findings demonstrate that stimulation of biochemical events in both source and sink tissues is associated with Sh2r6hs expression.

The maize Sh2r6hs ADP-glucose pyrophosphorylase (AGP) large subunit confers enhanced AGP properties in transgenic wheat ( Triticum aestivum)

The rate of cereal seed starch biosynthesis is determined largely by the activity of starch biosynthetic enzymes within the endosperm. The heterotetrameric allosteric enzyme ADP-glucose pyrophosphorylase (AGP) controls the first committed step in starch synthesis, and is inhibited by phosphate (P i) and activated by 3-PGA. An altered AGP large subunit ( Sh2r6hs) from maize containing two alterations relative to the wild-type maize Sh2 sequence was introduced into wheat. The rev6 alteration confers reduced P i inhibition and decreased heat stability in maize and the hs alteration has been shown to increase AGP subunit interactions and enzyme stability in Escherichia coli. We have previously shown that low-level expression of Sh2r6hs under control of the maize Sh2 promoter increases yield in wheat and rice. Our objective here was to examine how Sh2r6hs affects AGP activity and yield in wheat and whether further yield increases were possible with greater Sh2r6hs expression. We therefore developed an additional population of transgenic wheat expressing SH2R6HS under control of the endosperm specific wheat Glutenin ( Glu) promoter. Yield increases in high-expressing Glu promoter Sh2r6hs lines were comparable to those with the Sh2 promoter despite the fact that the Glu promoter confers ∼20 times higher levels of Sh2r6hs expression than the Sh2 promoter and five times more SH2R6HS accumulation versus native wheat large AGP subunits. However, the high expression allowed endosperm AGP kinetic analysis. The I 0.5 of wheat AGP was increased from 2.0 to 4.1 mM P i by SH2R6HS expression and the A 0.5 was decreased from 0.82 to 0.31 mM 3-PGA. Two properties of Sh2r6hs AGP were identified that indicate greater subunit stability: wheat AGP small subunit levels were higher without variation in small subunit transcript levels, and in vitro activity was twice as great as untransformed AGP activity after heat treatment. Both r6 and hs alterations act independently and synergistically to modify AGP allosteric-regulation, increase AGP subunit stability, and increase yield in plants expressing Sh2r6hs.

Molecular Cloning of ADP-Glucose Pyrophosphorylase Large Subunit cDNA from Oncidium

A full-length cDNA for ADP-glucose pyrophosphorylase large subunit (AGPL) was isolated from tropical epiphytic orchid Oncidium hybrid Goldiana. The cDNA was 1754 bp in length with an open reading frame of 1551 bp encoding 517 amino acids. The deduced amino acid sequence showed 73 % identity with those of potato isoform 3 (AGPL3) and Arabidopsis thaliana isoform 1 (AGPL1), 71 % identity with that of barley isoform BLPL. RT-PCR analysis showed that AGPL was expressed in mature leaf, immature leaf, developing inflorescence and flower of Oncidium. No expression was detected in roots.

Characterization of a gene from chromosome 1B encoding the large subunit of ADPglucose pyrophosphorylase from wheat: evolutionary divergence and differential expression ofAgp2genes between leaves and developing endosperm

A full-length genomic clone containing the gene encoding the large subunit of the ADPglucose pyrophosphorylase (Agp2), was isolated from a genomic library prepared from etiolated shoots of hexaploid wheat (Triticum aestivum L., cv, Chinese Spring). The coding region of this gene is identical to one of the cDNA clones previously isolated from a developing wheat grain cDNA library and is therefore an actively transcribed gene. The sequence represented by the cDNA spans 4.8 kb of the genomic clone and contains 15 introns. 2852 bp of DNA flanking the transcription start site of the gene was cloned upstream of the GUS (beta-glucuronidase) reporter gene. This Agp2::GUS construct and promoter deletions were used to study the pattern of reporter gene expression in both transgenic tobacco and wheat plants. Histochemical analysis of GUS expression in transgenic tobacco demonstrated that the reporter gene was expressed in guard cells of leaves and throughout the seed. In transgenic wheat, reporter gene expression was confined to the endosperm and aleurone with no expression in leaves. The cloned Agp2 gene was located to chromosome 1B by gene-specific PCR with nullisomic-tetrasomic lines. Northern analysis demonstrated that the Agp2 genes are differentially expressed in leaves and developing endosperm; while all three classes of Agp2 genes are transcribed in developing wheat grain endosperm, only one is transcribed in leaves. The differences between the Agp2 genes are discussed in relation to the evolution of hexaploid wheat.

Seed yield and plant biomass increases in rice are conferred by deregulation of endosperm ADP-glucose pyrophosphorylase.

In this work we test the hypothesis that yield of rice ( Oryza sativa L.) can be enhanced by increasing endosperm activity of ADP-glucose pyrophosphorylase (AGP), a key enzyme in starch biosynthesis. The potential for increases in yield exist because rice initiates more seeds than are taken to maturity and possesses excess photosynthetic capacity that could be utilized if there were more demand for assimilate. Following an approach already shown to be successful in wheat, experiments were designed to increase demand for assimilate by increasing the capacity for starch synthesis in endosperm. This was accomplished by transforming rice with a modified maize AGP large subunit sequence ( Sh2r6hs) under control of an endosperm-specific promoter. This altered subunit confers upon AGP decreased sensitivity to allosteric inhibition by inorganic phosphate (Pi) and enhanced heat stability, potentially leading to higher AGP activity in vivo. The Sh2r6hs transgene increased AGP activity in developing endosperm by 2.7-fold in the presence of Pi. Increases in AGP activity in transgenic seeds compared with controls were maximal between 10-15 days after anthesis. Starch content of individual seeds at harvest was not increased, but seed weight per plant and total plant biomass were each increased by more than 20%. Increased endosperm AGP activity thus stimulates setting of additional seeds and overall plant growth rather than increasing yield of seeds already set. Results demonstrate that deregulation of endosperm AGP increases overall plant sink strength, leading to larger, more productive plants in a manner similar to that in wheat having similar genetic modification.

Enhanced ADP-glucose pyrophosphorylase activity in wheat endosperm increases seed yield.

Yield in cereals is a function of seed number and weight; both parameters are largely controlled by seed sink strength. The allosteric enzyme ADP-glucose pyrophosphorylase (AGP) plays a key role in regulating starch biosynthesis in cereal seeds and is likely the most important determinant of seed sink strength. Plant AGPs are heterotetrameric, consisting of two large and two small subunits. We transformed wheat (Triticum aestivum L.) with a modified form of the maize (Zea mays L.) Shrunken2 gene (Sh2r6hs), which encodes an altered AGP large subunit. The altered large subunit gives rise to a maize AGP heterotetramer with decreased sensitivity to its negative allosteric effector, orthophosphate, and more stable interactions between large and small subunits. The Sh2r6hs transgene was still functional after five generations in wheat. Developing seeds from Sh2r6hs transgenic wheat exhibited increased AGP activity in the presence of a range of orthophosphate concentrations in vitro. Transgenic Sh2r6hs wheat lines produced on average 38% more seed weight per plant. Total plant biomass was increased by 31% in Sh2r6hs plants. Results indicate increased availability and utilization of resources in response to enhanced seed sink strength, increasing seed yield, and total plant biomass.

Induction of ApL3 expression by trehalose complements the starch-deficient Arabidopsis mutant adg2-1 lacking ApL1, the large subunit of ADP-glucose pyrophosphorylase.

The disaccharide trehalose has strong effects on plant metabolism and development. In Arabidopsis seedlings, growth on trehalose-containing medium leads to an inhibition of root elongation, an accumulation of starch in the shoots, an increased activity of ADP-Glc pyrophosphorylase (AGPase), and an induction of the expression of the AGPase gene, ApL3 (A. Wingler, T. Fritzius, A. Wiemken, T. Boller, R.A. Aeschbacher [2000] Plant Physiol 124: 105-114). We used Arabidopsis mutants deficient in starch synthesis to examine whether the primary effect of trehalose was to affect carbohydrate allocation by the induction of AGPase in the photosynthetic tissue. In a mutant lacking the large AGPase subunit, ApL1, (adg2-1 mutant) growth on trehalose restored AGPase activity and led to a strong accumulation of starch in the shoots. In contrast, starch synthesis could not be induced in a mutant lacking the small AGPase subunit, ApS, (adg1-1 mutant) or in a mutant lacking plastidic phosphoglucomutase (pgm1-1 mutant). These results indicate that ApL3 can substitute for ApL1 in the AGPase complex. In addition, root elongation in the mutants, especially in the adg1-1 mutant, was partially resistant to trehalose, suggesting that the induction of ApL3 expression and the resulting accumulation of starch in the shoots were partially responsible for the effects of trehalose on the growth of wild-type plants.

Presence of multiple cDNAs encoding an isoform of ADP-glucose pyrophosphorylase large subunit from sweet potato and characterization of expression levels.

Three cDNAs (iAGPLI-1, iAGPLI-2, and iAGPLI-3) encoding an isoform of AGPase large subunit were isolated from a sweet potato cDNA library constructed from tuberous root tissue. iAGPLI-1 was 2,161 bp in length and contained an open reading frame of 517 amino acids with a calculated molecular mass of 57,689 Da. iAGPLI-2 and iAGPLI-3 were 1,804 and 1,524 bp in length, respectively, and contained partial open reading frames of 490 and 385 amino acids. Deduced amino acid sequence comparison analysis showed that iAGPLI-1 has sequence identity with iAGPLI-2 (97.9) and iAGPLI-3 (98.7%) while iAGPLI-2 and iAGPLI-3 have 96.8% sequence identity. iAGPLI-1 had the highest sequence identity of 77.8% with potato AGPase (sAGPL1). Steady-state levels of iAGPLI-1 transcripts were expressed predominantly in the stem, and moderately in the tuberous root, but not in either the roots or leaves. However, AGPase activity was present in all tissues. The expression level in the stem declined dramatically after a 12 h incubation in the dark to nearly 3% of the value under light, although the activity under a dark condition remained at half the levels in light. The activity levels were not correlated with the transcript levels. iAGPL transcripts in leaves were induced by sucrose feeding but not by glucose or fructose. Therefore, the expression of iAGPLI-1 is regulated in stem tissue preferentially and by sucrose. Southern blot analysis showed that the sweet potato genome contained several copies of iAGPLI gene probably due to polyploidy.

Quantitative trait loci affecting amylose, amylopectin and starch content in maize recombinant inbred lines

The loci explaining the variability of quantitative traits related to starch content and composition (amylose, amylopectin and water soluble fraction) were searched for in maize kernels. Multifactorial genetic methods were used to detect and locate QTLs (quantitative trait loci) on a genetic map consisting mainly of RFLP markers for genes with known function. The genetic material was recombinant inbred lines originating from parents differing in starch structure (dent vs. flint). Kernels were harvested from field grown plants for two successive years and under two pollination systems. Main effect and epistasis QTLs were detected using two methods, composite interval mapping (MQTL) and ANOVA. Despite large year-to-year differences, physiologically meaningful co-locations were observed between trait QTLs. Moreover, the number of expressed sequences on our map allowed the search for co-locations between QTLs and genes involved in carbohydrate metabolism. The main co-location was between an amylose QTL and Shrunken 2 (SH2) locus, on chromosome 3 (SH2 encoding for the large subunit of ADPglucose pyrophosphorylase). The importance of this locus as a candidate gene for a starch QTL is in agreement with previous studies based either on QTL co-locations or on revertant analysis. Other co-locations were observed between amylose and amylopectin QTLs and the two loci of IVR1 invertase genes on chromosomes 2 and 10. Further comparison with previously detected QTLs for carbohydrate metabolism in maize leaves showed consistent co-location in map regions devoid of candidate genes, such as near chromosome 1S telomere. The possible contribution of regulatory genes in this region is discussed.

Molecular cloning and spatial expression of an ApL1 cDNA for the large subunit of ADP-glucose pyrophosphorylase from Arabidopsis thaliana.

A cDNA, ApL1a, corresponding to a homologue of the large subunit of ADP-glucose pyrophosphorylase (AGPase), has been isolated/characterised by screening a cDNA library prepared from leaves of Arabidopsis thaliana, followed by rapid amplification of cDNA 3'-ends (3'-RACE). Within the 1685 nucleotide-long sequence (excluding polyA tail), an open reading frame encodes a protein of 522 amino acids (aa), with a calculated molecular weight of 57.7 kDa. The derived aa sequence does not contain any discernible transit peptide cleavage site motif, similarly to two other recently sequenced full-length Arabidopsis homologues for AGPase, and shows ca. 58-78% identity to homologous proteins from other plants/tissues. The corresponding gene was found to be expressed in all tissues examined (rosette and stem leaves, stems, flowers and fruits). The ubiquitous expression of the gene is consistent with its critical role in starch synthesis in Arabidopsis.

Expression of a yeast-derived invertase in developing cotyledons of Vicia narbonensis alters the carbohydrate state and affects storage functions.

In plants the carbohydrate state provides signals to adjust metabolism to specific physiological conditions. Storage-active sink organs like seeds often contain high levels of sucrose. In order to change the sugar status during seed development a yeast-derived invertase gene was expressed in Vicia narbonensis under control of the LeguminB4 promoter. A signal sequence targeted the invertase to the apoplast in maturing embryos. In the cotyledons, sucrose was decreased whereas hexoses strongly accumulated. There was a major reduction of starch whereas proteins were less affected. Vacuoles of cotyledon cells were enlarged and dry seeds wrinkled. Transcripts and enzyme activity of sucrose synthase, the small and large subunit of ADP-glucose pyrophosphorylase as well as vicilin were downregulated. Sucrose phosphate synthase and legumin-mRNAs were not affected. Analysing single seeds with different sucrose levels revealed a positive correlation of sucrose concentration to mRNA levels of sucrose synthase and most pronounced to ADP-glucose pyrophosphorylase-mRNA levels as well as to starch content. Glucose on the other hand did not show any correlation. After feeding 14C-sucrose in vitro, the invertase-expressing cotyledons partitioned less carbon into starch compared to the wild-type. In the transgenic cotyledons, a relatively higher amount was directed into proteins compared to starch. We conclude that starch accumulation in developing cotyledons could be a function of sucrose concentration. Our results are consistent with a possible sucrose-mediated induction of storage-associated differentiation indicated by upregulation of specific genes of the starch synthesis pathway.

Molecular cloning and organ-specific expression of three isoforms of tomato ADP-glucose pyrophosphorylase gene

We isolated three cDNAs encoding different isoforms of ADP-glucose pyrophosphorylase (AGP) large submits from tomato plants. Three clones, designated AgpL1, AgpL2, and AgpL3 were 2019, 2105, and 1850 bp, respectively. The clones had a long, uninterrupted open reading frame with a start codon at the 5′ region and different copies of polyadenylation signal (AATAAA) at the 3′ region, deriving 57–58 kDa polypeptides. Sequence comparison and phylogenetic analysis revealed that the three isoforms represented different types of AGP large subunits, AgpL1 was strongly expressed in stems and weakly in roots. Accumulation of AgpL1 transcripts was found even in unpollinated ovaries and sustained at the early stages of fruit development. A pgL2 was expressed in roots and fruits. AgpL3 was exclusively expressed in leaves. The present study suggests that the three isoforms of tomato AGP large subunits are organ-specific in their expressions.

Molecular cloning and expression of the large subunit of ADP-glucose pyrophosphorylase from barley ( Hordeum vulgare ) leaves

A cDNA clone, blpl14, corresponding to the large subunit of ADP-glucose pyrophosphorylase (AGPase), has been isolated from a cDNA library prepared from leaves of barley ( Hordeum vulgare L.). An open reading frame encodes a protein of 503 aa, with a calculated molecular weight of 54 815. The derived aa sequence contains a putative transit peptide sequence, required for targeting to plastids, and has a highly conserved positioning of critical Lys residues that are believed to be involved in effector binding. The derived aa sequence shows 97% identity with the corresponding protein from wheat, but only 36% identity with AGPase from E. coli. The blpl14 gene is expressed predominantly in leaves and to a lesser degree in seed endosperm, but not roots, of barley.