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1.
C. H. Saravitz C. D. Boyer 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,73(4):489-495
Summary Vigorously growing suspension cultures of normal, amylose-extender (ae) and waxy (wx) maize endosperm were established from near isogenic lines of maize inbred A636. The recovery of the ability to produce vigorous cultures of ae and wx endosperm by backcrossing demonstrate the genetic control of endosperm growth in vitro. Phenotypic expression of the endosperm mutants in culture was studied by examining the properties of starch accumulated in endosperm cultures and starch from developing and mature kernels of the same genotype. After 9 months in culture, the amylose contents of the starch in normal callus tissue and normal endosperm tissue were not significantly different, 28.2% and 31.7%, respectively. Starch granules from normal cultures and endosperm stained blue-black with iodine and were round to polygonal in shape. The starches of wx endosperm and callus cultures contained no amylose, and wx starch granules stained brown-orange with iodine. Although, wx starch granules were primarily round, a few granules with jagged edges were observed in starch samples isolated from cultures and kernels. The percent amylose in starch from ae callus was significantly lower than the amylose content of starch from ae endosperm tissue, 39.9% and 67.7%, respectively. Starch granules from ae endosperm and cultures were smaller than normal and wx starch granules. Irregular starch granules which are typical of ae endosperm were present in ae callus tissue, but were less frequently observed. We conclude that specific endosperm mutant phenotypes are expressed in vitro.Supported in part by the United States Department of Agriculture Competitive Grant 85-CRCR-1-1740. Contribution No. 94, Department of Horticulture. The Pennsylvania State University. Authorized for publication as paper No. 7373 in the journal series of the Pennsylvania Agricultural Experiment Station 相似文献
2.
Roles of isoamylase and ADP-glucose pyrophosphorylase in starch granule synthesis in rice endosperm 总被引:5,自引:0,他引:5
Kawagoe Y Kubo A Satoh H Takaiwa F Nakamura Y 《The Plant journal : for cell and molecular biology》2005,42(2):164-174
Amyloplast-targeted green fluorescent protein (GFP) was used to monitor amyloplast division and starch granule synthesis in the developing endosperm of transgenic rice. Two classical starch mutants, sugary and shrunken, contain reduced activities of isoamylase1 (ISA1) and cytosolic ADP-glucose pyrophosphorylase, respectively. Dividing amyloplasts in the wild-type and shrunken endosperms contained starch granules, whereas those in sugary endosperm did not contain detectable granules, suggesting that ISA1 plays a role in granule synthesis at the initiation step. The transition from phytoglycogen to sugary-amylopectin was gradual in the boundary region between the inner and outer endosperms of sugary. These results suggest that the synthesis of sugary-amylopectin and phytoglycogen involved a stochastic process and that ISA1 activity plays a critical role in the stochastic process in starch synthesis in rice endosperm. The reduction of cytosolic ADP-glucose pyrophosphorylase activity in shrunken endosperm did not inhibit granule initiation but severely restrained the subsequent enlargement of granules. The shrunken endosperm often developed pleomorphic amyloplasts containing a large number of underdeveloped granules or a large cluster of small grains of amyloplasts, each containing a simple-type starch granule. Although constriction-type divisions of amyloplasts were much more frequent, budding-type divisions were also found in the shrunken endosperm. We show that monitoring GFP in developing amyloplasts was an effective means of evaluating the roles of enzymes involved in starch granule synthesis in the rice endosperm. 相似文献
3.
N.K. Matheson 《Phytochemistry》1975,14(9):2017-2021
After removal of granular starch at low centrifugal force, the centrifugation, at increasing forces, of aqueous extracts of su1 corn gave a series of α-glucan precipitates that contained amylose. The amylose content decreased as the force increased. In contrast, in normal corn all the α-glucan precipitated as starch granules at low forces. In the sweet corn precipitates, apart from the granular starch, the branched α-glucan was phytoglycogen. The MW of this decreased as the proportion of amylose decreased. It appears that, as well as starch granules and soluble phytoglycogen, sweet corn contains granules, smaller than starch, of a range of sizes, and these are made up of phytoglycogen and amylose. As granule size decreases, so does the MW of the phytoglycogen and the content of amylose. A method of quantitative extraction of starch giving minimal depolymerization is described. The isopotential iodine absorption of a quantitative extract of sweet corn flour indicated that the total ratio of linear (amylose) fraction to branched (amylopectin + phytoglycogen) fraction was near the normal value of 1:4. 相似文献
4.
5.
In maize, three isoforms of starch-branching enzyme, SBEI, SBEIIa, and SBEIIb, are encoded by the Sbe1a, Sbe2a, and Amylose extender (Ae) genes, respectively. The objective of this research was to explore the effects of null mutations in the Sbe1a and Ae genes alone and in combination in wx background on kernel characteristics and on the morphology and physical behavior of endosperm starch granules. Differences in kernel morphology and weight, starch accumulation, starch granule size and size distribution, starch microstructure, and thermal properties were observed between the ae wx and sbe1a ae wx plants but not between the sbe1a wx mutants when compared to wx. Starch from sbe1a ae wx plants exhibited a larger granule size with a wider gelatinization temperature range and a lower endotherm enthalpy than ae wx. Microscopy shows weaker iodine staining in sbe1a ae wx starch granules. X-ray diffraction revealed A-type crystallinity in wx and sbe1a wx starches and B-type in sbe1a ae wx and ae wx. This study suggests that, while the SBEIIb isoform plays a dominant role in maize endosperm starch synthesis, SBEI also plays a role, which is only observable in the presence of the ae mutation. 相似文献
6.
Physicochemical properties and development of wheat large and small starch granules during endosperm development 总被引:3,自引:0,他引:3
Cunxu Wei Jun Zhang Yifang Chen Weidong Zhou Bin Xu Youping Wang Jianmin Chen 《Acta Physiologiae Plantarum》2010,32(5):905-916
Wheat mature seeds have large, lenticular A-type starch granules, and small, spherical B-type and irregular C-type starch
granules. During endosperm development, large amyloplasts came from proplastid, divided and increased in number through binary
fission from 4 to 12 days after flowering (DAF). Large starch granules formed and developed in the large amyloplast. One large
amyloplast had only one large starch granule. Small amyloplasts came from the protrusion of large amyloplast envelope, divided
and increased in number through envelope protrusion after 12 DAF. B-type starch granules formed and developed in small amyloplast
from 12 to 18 DAF, C-type starch granules formed and developed in small amyloplast after 18 DAF. Many B- and C-type starch
granules might form and develop in one small amyloplast. The amyloplast envelopes were asynchronously degraded and starch
granules released into cell matrix when amyloplasts were full of starch granules. Apparent amylose contents of large starch
granules were higher than that of small starch granules, and increased with endosperm development. The swelling powers and
crystallinity of large starch granule were lower than that of small starch granules, and decreased with endosperm development.
Small starch granules displayed broader gelatinization temperature ranges than did large starch granules. 相似文献
7.
Debranching enzymes, which hydrolyze α-1 and 6-glucosidic linkages in α-polyglucans, play a dual role in the synthesis and degradation of starch in plants. A transposon-inserted rice mutant of isoamylase3 (isa3) contained an increased amount of starch in the leaf blade at the end of the night, indicating that ISA3 plays a role in the degradation of transitory starch during the night. An epitope-tagged ISA3 expressed in Escherichia coli exhibited hydrolytic activity on β-limit dextrin and amylopectin. We investigated whether ISA3 plays a role in amyloplast development and starch metabolism in the developing endosperm. ISA3-green fluorescent protein (GFP) fusion protein expressed under the control of the rice ISA3 promoter was targeted to the amyloplast stroma in the endosperm. Overexpression of ISA3 in the sugary1 mutant, which is deficient in ISA1 activity, did not convert water-soluble phytoglycogen to starch granules, indicating that ISA1 and ISA3 are not functionally redundant. Both overexpression and loss of function of ISA3 in the endosperm generated pleomorphic amyloplasts and starch granules. Furthermore, chloroplasts in the leaf blade of isa3 seedlings were large and pleomorphic. These results suggest that ISA3 facilitates starch metabolism and affects morphological characteristics of plastids in rice. 相似文献
8.
Molecular Characterization of the waxy Locus of Rice (Oryza sativa) 总被引:10,自引:0,他引:10
9.
Analysis of Endosperm Sugars in a Sweet Corn Inbred (Illinois 677a) Which Contains the Sugary Enhancer (se) Gene and Comparison of se with Other Corn Genotypes 总被引:3,自引:3,他引:0
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The endosperm sugars of a new corn (Zea mays L.) mutant, sugary enhancer (se), were analyzed by gas-liquid chromatography and were compared with sugars of other genotypes. Illinois 677a, a sugary (su) inbred containing the se gene, was high in sucrose and was distinguished from all of the other genotypes by its high maltose content. During kernel development, the maltose content of IL677a increased to 3.28% dry weight at 40 days postpollination and remained high at the dry mature stage, whereas `Silver Queen,' a high quality sugary (su) hybrid not possessing the se gene, showed no such trend in maltose accumulation. Sucrose, fructose, and glucose decreased during kernel development in `Silver Queen' and IL677a from 19 days postpollination until the dry mature stage. The slow drying characteristic and the reduced starch content previously reported for maturing seeds of IL677a may be related to the maltose accumulation reported here. 相似文献
10.
Jian Liu Tingzhao Rong Wanchen Li 《Molecular breeding : new strategies in plant improvement》2007,20(2):93-102
Four pairs of specific PCR primers have been designed on the basis of the sequence of the granule-bound starch synthase gene
(GBSS; dominant non-waxy gene Wx) and used to amplify its homologous sequence from thirteen waxy and two non-waxy inbred lines. Results from electrophoresis
indicated that the recessive waxy gene was wx, derived from the dominant non-waxy gene Wx by mutation at its 3′ end. The sequence of the mutated 3′ end was amplified by the TAIL-PCR technique. Sequence alignment
showed that the mutation of the wx gene was caused by transposition of the aldehyde dehydrogenase gene rf2. Two pairs of specific primers were designed on the basis of the sequence difference between the dominant gene Wx and its mutated recessive allele wx and used as intragenic selection markers to identify individual plants of genotypes WxWx, Wxwx, and wxwx by PCR amplification from the segregating population of the F2 generation crossed between waxy and non-waxy inbred lines. Iodine solution staining and starch component assay showed that
all the 35 F2 plants identified as genotype WxWx produced non-waxy kernels of the F3 generation and that all 33 F2 plants identified as genotype wxwx produced waxy kernels of the F3 generation. This result can be used to improve the selection efficiency of waxy maize breeding and for selection of other
single genes and major polygenes. 相似文献
11.
Post-Domestication Selection in the Maize Starch Pathway 总被引:1,自引:0,他引:1
Longjiang Fan Jiandong Bao Yu Wang Jianqiang Yao Yijie Gui Weiming Hu Jinqing Zhu Mengqian Zeng Yu Li Yunbi Xu 《PloS one》2009,4(10)
Modern crops have usually experienced domestication selection and subsequent genetic improvement (post-domestication selection). Chinese waxy maize, which originated from non-glutinous domesticated maize (Zea mays ssp. mays), provides a unique model for investigating the post-domestication selection of maize. In this study, the genetic diversity of six key genes in the starch pathway was investigated in a glutinous population that included 55 Chinese waxy accessions, and a selective bottleneck that resulted in apparent reductions in diversity in Chinese waxy maize was observed. Significant positive selection in waxy (wx) but not amylose extender1 (ae1) was detected in the glutinous population, in complete contrast to the findings in non-glutinous maize, which indicated a shift in the selection target from ae1 to wx during the improvement of Chinese waxy maize. Our results suggest that an agronomic trait can be quickly improved into a target trait with changes in the selection target among genes in a crop pathway. 相似文献
12.
Soluble isoforms of starch synthase and starch-branching enzyme also occur within starch granules in developing pea embryos 总被引:9,自引:1,他引:8
Kay Denyer Christopher Sidebottom Christopher M. Hylton Alison M. Smith 《The Plant journal : for cell and molecular biology》1993,4(1):191-198
Developing wild-type pea embryos contain two major isoforms of starch synthase and two isoforms of starch-branching enzyme. One of the starch synthases and both starch-branching enzymes occur both in the soluble fraction and tightly bound to starch granules. The other starch synthase, which is very similar to the waxy proteins of other species, is exclusively granule-bound. It is inactive when solubilized in a native form from starch granules, but activity is recovered when the SDS-denatured protein is reconstituted from polyacrylamide gels.
Evidence is presented which indicates that all of these proteins become incorporated within the structure of the granule as it grows. It is proposed that the granule-bound waxy protein is active in vivo at the granule surface, whereas the remaining proteins are active in the soluble fraction of the amyloplast. The proteins become trapped within the granule matrix as the polymers they synthesize crystallize around them, and they probably play no further part in polymer synthesis. 相似文献
Evidence is presented which indicates that all of these proteins become incorporated within the structure of the granule as it grows. It is proposed that the granule-bound waxy protein is active in vivo at the granule surface, whereas the remaining proteins are active in the soluble fraction of the amyloplast. The proteins become trapped within the granule matrix as the polymers they synthesize crystallize around them, and they probably play no further part in polymer synthesis. 相似文献
13.
G. G. Doyle 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,71(4):585-594
Summary Allotetraploidization is the creation of synthetic allotetraploids. The allotetraploidization of maize can be accomplished by concentrating DPA (differential pairing affinity) factors into stocks by a recurrent selection breeding system. Selection is based on pairing configuration frequencies and altered genetic ratios that reflect DPA. Both an observed decline in the quadrivalent frequency per meiocyte from 8.10 to 7.31 and genetic data disclosing a reduction in the average frequency of recessive waxy (wx wx) pollen from Wx Wx wx wx plants from 17.48% to 13.35%, indicate considerable progress has been made toward allotetraploidization. A simple model for the effect of DPA on chromosome pairing and genetic ratios is presented.Contribution from the Agricultural Research Service, U.S. Department of Agriculture, University of Missouri, Missouri Agricultural Experiment Station, Journal Series No. 9806 相似文献
14.
Tadashi Baba Takeshi Yamamoto Yuji Arai Masanobu Yokota Tatsuro Itoh 《Phytochemistry》1981,20(7):1513-1517
In an attempt to investigate starch biosynthesis of amylomaize, the endosperm starches from four genotypes with different doses of amylose-extender (ae) between 0 and 3 were isolated at 14, 18, 22, 28, and 36 days after pollination, and their properties were examined. Gene effects of ae on the endosperm starches were found in the apparent amylose content from measurements of iodine binding capacity and in the elution pattern from fractionation of starches debranched by isoamylase on Sephadex G-75. With increasing doses of ae, the lengths of two side-chain fractions of amylopectin in the original starch granule and the carbohydrate content of shorter side-chain fraction both increased. However, the length of each side chain fraction varied little between 14 and 36 days in all genotypes. In addition, the amylose content in ae homozygous at the 14-day stage was ca 24 % lower than the value of amylose and intermediate fractions in the original starch granule. 相似文献
15.
Starch
granules from maize (Zea mays) contain a characteristic
group of polypeptides that are tightly associated with the starch
matrix (C. Mu-Forster, R. Huang, J.R. Powers, R.W. Harriman, M. Knight,
G.W. Singletary, P.L. Keeling, B.P. Wasserman [1996] Plant Physiol
111: 821–829). Zeins comprise about 50% of the granule-associated
proteins, and in this study their spatial distribution within the
starch granule was determined. Proteolysis of starch granules at
subgelatinization temperatures using the thermophilic protease
thermolysin led to selective removal of the zeins, whereas
granule-associated proteins of 32 kD or above, including the waxy
protein, starch synthase I, and starch-branching enzyme IIb, remained
refractory to proteolysis. Granule-associated proteins from maize are
therefore composed of two distinct classes, the surface-localized zeins
of 10 to 27 kD and the granule-intrinsic proteins of 32 kD or higher.
The origin of surface-localized δ-zein was probed by comparing
δ-zein levels of starch granules obtained from homogenized whole
endosperm with granules isolated from amyloplasts. Starch granules from
amyloplasts contained markedly lower levels of δ-zein relative to
granules prepared from whole endosperm, thus indicating that δ-zein
adheres to granule surfaces after disruption of the amyloplast
envelope. Cross-linking experiments show that the zeins are deposited
on the granule surface as aggregates. In contrast, the
granule-intrinsic proteins are prone to covalent modification, but do
not form intermolecular cross-links. We conclude that individual
granule intrinsic proteins exist as monomers and are not deposited in
the form of multimeric clusters within the starch matrix.It has long been known that starch granules contain bound
polypeptides, with protein levels of isolated starch granules from
maize (Zea mays) ranging from 0.3 to 1.0% based upon
measurement of N2 (May, 1987). A recent study by our
laboratory demonstrates that isolated starch granules from maize
contain several dozen strongly bound polypeptides (Mu-Forster et al.,
1996). The granule-associated proteins include starch-biosynthetic
enzymes such as the waxy protein, SSI, and SBEIIb. These polypeptides
are not removed from intact starch granules by protease treatment or
detergent washing; therefore, they are believed to bind to the starch
and to become irreversibly entrapped within the starch
matrix.Based upon staining intensities of polypeptides extracted from the
starch granule (Mu-Forster et al., 1996), approximately one-half of the
granule-associated proteins in maize consist of low-molecular-mass
polypeptides ranging between 10 and 27 kD. These bands fall within the
size range displayed by the zein storage proteins, however, the spatial
distribution of these polypeptides within the starch granule is
unknown. Zeins have been defined as alcohol-soluble proteins that occur
principally in protein bodies of maize endosperm and that may or may
not require reduction before extraction (Wilson, 1991). The association
of zeins with starch granules during endosperm development would not be
expected because zein genes do not contain transit peptides that would
target these proteins through the amyloplast envelope into the
amyloplast stroma.The objective of this study was to establish the topology of
granule-associated zeins in starch granules from maize endosperm. To
accomplish this, it was necessary to distinguish between
surface-localized and internalized polypeptides. Our working hypothesis
defines polypeptides localized at the starch granule surface as those
that are susceptible to hydrolysis upon treatment of intact granules
with exogenous proteases. Conversely, internal granule proteins are
defined as those that (a) become susceptible to proteolysis only
following thermal disruption of the starch matrix, and (b) resist
extraction by 2% SDS at room temperatures (Denyer et al., 1993; Rahman
et al., 1995; Mu-Forster et al., 1996).In this study we were able to distinguish between surface-localized and
internalized granule-associated polypeptides in starch granules
from maize endosperm by use of the thermophilic protease thermolysin.
Thermolysin is well suited for this purpose because it is highly active
at starch-gelatinization temperatures, and has also been shown to
effectively hydrolyze hydrophobic proteins located at the surfaces of
chloroplasts and other subcellular organelles (Cline et al., 1984; Xu
and Chitnis, 1995). Upon extended incubation of intact starch granules
with thermolysin at subgelatinization temperatures, we found that zeins
were selectively removed from the starch granule surface. All other
granule-associated polypeptides remained inaccessible to proteolytic
attack or to extraction by 2% SDS, unless the starch matrix was first
disrupted by gelatinization. Our results distinguish between the
surface-localized and granule-intrinsic proteins of maize endosperm,
and establish that zeins are localized at the starch-granule surface.
In addition, cross-linking experiments were conducted to determine
nearest-neighbor relationships among zein subunits localized at the
granule surface and granule intrinsic polypeptides localized within the
starch matrix. 相似文献
16.
Jessica M. M. Adams Pauline J. M. Teunissen Geoff Robson Nigel Dunn-Coleman Iain S. Donnison 《Bioenergy Research》2012,5(2):330-340
The conversion of maize (corn) kernels to bio-ethanol is an energy-intensive process involving many stages. One step typically required is the liquefaction of the ground kernel to enable enzyme hydrolysation of the starch to glucose. The enzyme blends STARGEN? (Genencor) are capable of hydrolysing starch granules without liquefaction, reducing energy inputs and increasing efficiency. Studies were conducted on maize starch mutants amylose extender 1 (ae1), dull 1 (du1) and waxy 1 (wx1) in the inbred line Oh43 to determine whether different maize starches affected hydrolysation rates by STARGEN? 001 and STARGEN? 002. All mutants contained similar proportions of starch in the kernel but varied in the amylose to amylopectin ratio. Ground maize kernels were incubated with STARGEN? 001 and viewed using scanning electron microscopy to examine the hydrolysis action of STARGEN? 001 on the starch granules. The ae1 mutant exhibited noticeably less enzymic hydrolysis action, on the granules visualised, than wx1 and background line Oh43. Kernels were batch-fermented with STARGEN? 001 and STARGEN? 002. The ae1 mutant exhibited a 50% lower ethanol yield compared to the wx1 mutant and background line. A final study compared hydrolysation rates of STARGEN? 001 and STARGEN? 002 on purified maize starch, amylopectin and amylose. Though almost twice the amylopectin was hydrolysed using STARGEN? 002 than STARGEN? 001 in this trial, fermentations using STARGEN? 002 resulted in lower ethanol yields than fermentations using STARGEN? 001. Both STARGEN? enzyme blends were more suitable for the fermentation of high amylopectin maize starches than high amylose starches. 相似文献
17.
Starch granule initiation and growth are altered in barley mutants that lack isoamylase activity 总被引:23,自引:0,他引:23
Burton RA Jenner H Carrangis L Fahy B Fincher GB Hylton C Laurie DA Parker M Waite D van Wegen S Verhoeven T Denyer K 《The Plant journal : for cell and molecular biology》2002,31(1):97-112
Two mutant lines of barley, Risø 17 and Notch‐2, were found to accumulate phytoglycogen in the grain. Like the sugary mutants of maize and rice, these phytoglycogen‐accumulating mutants of barley lack isoamylase activity in the developing endosperm. The mutants were shown to be allelic, and to have lesions in the isoamylase gene, isa1 that account for the absence of this enzyme. As well as causing a reduction in endosperm starch content, the mutations have a profound effect on the structure, number and timing of initiation of starch granules. There are no normal A‐type or B‐type granules in the mutants. The mutants have a greater number of starch granules per plastid than the wild‐type and, particularly in Risø 17, this leads to the appearance of compound starch granules. These results suggest that, as well as suppressing phytoglycogen synthesis, isoamylase in the wild‐type endosperm plays a role in determining the number, and hence the form, of starch granules. 相似文献
18.
J. W. Paulis J. A. Bietz T. P. Bogyo T. C. Nelsen L. L. Darrah M. S. Zuber 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,85(4):407-414
Summary Zeins, the major endosperm proteins in maize (Zea mays L.), are deficient in the essential amino acids lysine and tryptophan. Some mutant genes, like opaque-2 (o2) and floury-2 (fl2), reduce the levels of A- and B-zeins, thereby improving maize's nutritional value. Other mutants, such as amylose-extender (ae), floury-1 (fl1), soft starch (h), dull-1 (du), shrunken-1 (sh1), sugary-1 (su1), sugary-2 (su2), and waxy (wx), primarily affect starch composition, but also alter zein composition. We undertook this study to examine the effects of some of these mutant genes on A/B-zein composition and to study the interactions of these genes in double-mutant combinations. Endosperm prolamins were extracted from inbred B37, ten near-isogenic single mutants (ae, du, fl1, fl2, h, o2, sh1, su1, su2, and wx), and most double-mutant combinations. Zeins in these extracts were fractionated by reversed-phase highperformance liquid chromatography (RP-HPLC) into 22–24 peaks. Of the resulting 22 major peaks the areas of 16 (per milligram endosperm) were significantly affected by individual mutant genes relative to the zein composition of the normal inbred. In combination these genes exhibited significant epistatic interactions in regulating the expression of individual A/B zeins. Epistatic interactions were judged to be significant when the amount of a peak in a double mutant differed from the averages for the peak in the two respective single mutants. The o2 gene, alone and in combination with other mutant genes, significantly decreased the amounts of many individual zeins. The effect of the o2 gene was the greatest of all the genes examined. Various clustering techniques were used to see if mutant effects could be grouped; among these was principal component analysis, a multivariate statistical technique that analyzes all peak sizes simultaneously. Three-dimensional scatter graphs were constructed based on the first three principal components. For the single mutants, these showed no relationships to gene actions; for the double mutants, however, this technique showed that four single mutants, o2, sh1, su1 and su2, had the greatest effects on zein composition when combined with each other and with the remaining six single mutants.Presented at the XVI International Congress of Genetics, Toronto, Canada, August 20–27, 1988. The mention of firm names or trade products does not imply that they are endorsed or recommended by the USDA over other brands or similar products not mentioned 相似文献
19.
Differential regulation of waxy gene expression in rice endosperm 总被引:36,自引:0,他引:36
Y. Sano 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,68(5):467-473
Summary In order to examine the effects of different alleles on the gene expression at the waxy locus, the Wx gene product which controls the synthesis of amylose was isolated from endosperm starch of rice plants and analysed by electrophoretic techniques. The major protein bound to starch granules was absent in most of waxy strains and increased with the number of Wx alleles in triploid endosperms, suggesting that the major protein is the Wx gene product. In addition to wx alleles which result in the absence or drastic reduction of the Wx gene product and amylose, differentiation of Wx alleles seemed to have occurred among nonwaxy rice strains. At least two Wx alleles with different efficiencies in the production of the major protein as well as amylose were detected. These alleles are discussed in relation to regulation of the gene expression. 相似文献
20.
C. D. Boyer 《American journal of botany》1981,68(5):659-665
Cell development and starch granule formation in seeds of three pea (Pisum sativum L.) genotypes, R/R Rb/Rb, r/r Rb/Rb, and R/R rb/rb, affecting cotyledon starch were compared. Cotyledon cells at 10 days after flowering were highly vacuolated and contained small protein bodies in the vacuoles and small oval starch granules in the cytoplasm in all three genotypes. Gradients of cell development from the center to the periphery of the cotyledon and toward the cotyledon-hypocotyl axis persisted through the cell enlargement, reserve synthesis, and into the maturation stages of cotyledon development. By 14 days after flowering, many small vacuoles lined with protein deposits had been formed. Vacuoles were only observed in peripheral and basal cells by 18 days after flowering. Starch granules were oval and birefringent in all three genotypes at 10 days. Starch granules in R/R Rb/Rb and R/R rb/rb cotyledons expanded regularly remaining nearly oval and birefringent throughout development. In contrast, starch granules from r/r Rb/Rb cotyledons began to fragment by 14 days after flowering. This process began as a single fissure, followed by a second fissure usually at or near right angles. Finally, because of the fragmentation, the granules appeared compound, and only a portion of the granule was birefringent. All genotypes contained nearly equal volumes of liquid endosperm and embryo at 10 days after flowering. In addition, a layer of parenchyma tissue (ovular and/or endospermic) inside the seed coat was observed. Although, thin walled and poorly defined cytologically, the parenchyma cells contained large numbers of starch granules. These granules were a mixture of simple and compound types in all genotypes. By 18 days after flowering, the parenchyma tissue was reduced to a small layer of cell walls and all starch granules had been mobilized. 相似文献