Structural variability between starch granules in wild type and in ae high-amylose mutant maize kernels

2013 ◽  
Vol 97 (2) ◽  
pp. 458-468 ◽  
Author(s):  
Dongli Liu ◽  
Mary L. Parker ◽  
Nikolaus Wellner ◽  
Andrew R. Kirby ◽  
Kathryn Cross ◽  
...  
Keyword(s):  
Starch Granules ◽  
Wild Type ◽  
Structural Variability ◽  
High Amylose ◽  
Maize Kernels

scholarly journals Amylopectin Induces Fumonisin B1 Production by Fusarium verticillioides During Colonization of Maize Kernels

2005 ◽  
Vol 18 (12) ◽  
pp. 1333-1339 ◽  
Author(s):  
B. H. Bluhm ◽  
C. P. Woloshuk
Keyword(s):  
Quantitative Polymerase Chain Reaction ◽  
Fusarium Verticillioides ◽  
Animal Health ◽  
Fumonisin B1 ◽  
Polymerase Chain Reaction Analysis ◽  
Defined Medium ◽  
Wild Type ◽  
Fungal Genes ◽  
High Amylose ◽  
Maize Kernels

Fusarium verticillioides, a fungal pathogen of maize, produces fumonisin mycotoxins that adversely affect human and animal health. Basic questions remain unanswered regarding the interactions between the host plant and the fungus that lead to the accumulation of fumonisins in maize kernels. In this study, we evaluated the role of kernel endosperm composition in regulating fumonisin B1 (FB1) biosynthesis. We found that kernels lacking starch due to physiological immaturity did not accumulate FB1. Quantitative polymerase chain reaction analysis indicated that kernel development also affected the expression of fungal genes involved in FB1 biosynthesis, starch metabolism, and nitrogen regulation. A mutant strain of F. verticillioides with a disrupted α-amylase gene was impaired in its ability to produce FB1 on starchy kernels, and both the wild-type and mutant strains produced significantly less FB1 on a high-amylose kernel mutant of maize. When grown on a defined medium with amylose as the sole carbon source, the wild-type strain produced only trace amounts of FB1, but it produced large amounts of FB1 when grown on amylopectin or dextrin, a product of amylopectin hydrolysis. We conclude that amylopectin induces FB1 production in F. verticillioides. This study provides new insight regarding the interaction between the fungus and maize kernel during pathogenesis and highlights important areas that need further study.

scholarly journals A Rubisco-binding protein is required for normal pyrenoid number and starch sheath morphology inChlamydomonas reinhardtii

2019 ◽  
Vol 116 (37) ◽  
pp. 18445-18454 ◽  
Author(s):  
Alan K. Itakura ◽  
Kher Xing Chan ◽  
Nicky Atkinson ◽  
Leif Pallesen ◽  
Lianyong Wang ◽  
...  
Keyword(s):  
Surface Area ◽  
Structure And Function ◽  
Binding Motif ◽  
Starch Granules ◽  
Wild Type ◽  
Bisphosphate Carboxylase ◽  
Biophysical Mechanism ◽  
Mechanism Function ◽  
And Function

A phase-separated, liquid-like organelle called the pyrenoid mediates CO2fixation in the chloroplasts of nearly all eukaryotic algae. While most algae have 1 pyrenoid per chloroplast, here we describe a mutant in the model algaChlamydomonasthat has on average 10 pyrenoids per chloroplast. Characterization of the mutant leads us to propose a model where multiple pyrenoids are favored by an increase in the surface area of the starch sheath that surrounds and binds to the liquid-like pyrenoid matrix. We find that the mutant’s phenotypes are due to disruption of a gene, which we call StArch Granules Abnormal 1 (SAGA1) because starch sheath granules, or plates, in mutants lacking SAGA1 are more elongated and thinner than those of wild type. SAGA1 contains a starch binding motif, suggesting that it may directly regulate starch sheath morphology. SAGA1 localizes to multiple puncta and streaks in the pyrenoid and physically interacts with the small and large subunits of the carbon-fixing enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), a major component of the liquid-like pyrenoid matrix. Our findings suggest a biophysical mechanism by which starch sheath morphology affects pyrenoid number and CO2-concentrating mechanism function, advancing our understanding of the structure and function of this biogeochemically important organelle. More broadly, we propose that the number of phase-separated organelles can be regulated by imposing constraints on their surface area.

scholarly journals Production of very-high-amylose cassava by post-transcriptional silencing of branching enzyme genes

2018 ◽  
Author(s):  
Wenzhi Zhou ◽  
Shanshan Zhao ◽  
Shutao He ◽  
Qiuxiang Ma ◽  
Xinlu Lu ◽  
...  
Keyword(s):  
Amylose Content ◽  
Length Distribution ◽  
Constitutive Expression ◽  
Raw Material ◽  
Distribution Analysis ◽  
Starch Granules ◽  
Storage Roots ◽  
Chain Length Distribution ◽  
Transgenic Cassava ◽  
High Amylose

AbstractHigh amylose starch, a desired raw material in the starch industry, can be produced by plants deficient in the function of branching enzymes (BEs). Here we report the production of transgenic cassava plants with starches containing up to 50% amylose due to the constitutive expression of hair-pin dsRNAs targeting the BE1 or BE2 genes. A significant decrease in BE transcripts was confirmed in these transgenic plants by quantitative real-time RT-PCR. The absence of BE1 protein in the BE1-RNAi plant lines (BE1i) and a dramatically lower level of BE2 protein in the BE2-RNAi plant lines (BE2i) were further confirmed by Western blot assays. All transgenic plant lines were grown up in the field, but with reduced biomass production of the above-ground parts and storage roots compared to wild type (WT). Considerably high amylose content in the storage roots of BE2i plant lines was achieved, though not in BE1i plant lines. Storage starch granules of BE1i and BE2i plants had similar morphology as WT, however, the size of BE1i starch granules were bigger than that of WT. Comparisons of amylograms and thermograms of all three sources of storage starches revealed dramatic changes to the pasting properties and a higher melting temperature for BE2i starches. Glucan chain length distribution analysis showed a slight increase in chains of DP>36 in BE1i lines and a dramatic increase in glucan chains between DP 10-20 and DP>40 in BE2i lines, compared to that of WT starch. Furthermore, BE2i starches displayed a B-type X-ray diffraction pattern instead of the A-type pattern found in BE1i and WT starches. Therefore, cassava BE1 and BE2 function differently in storage root starch biosynthesis; silencing of cassava BE1 or BE2 caused various changes to starch physico-chemical properties and amylopectin structure. We also report that remarkably high amylose content in cassava starch has been first obtained in transgenic cassava by silencing of BE2 expression, thus showing a high potential for future industrial utilization.

Multiple effects of the starch synthase II mutation in developing wheat endosperm

2007 ◽  
Vol 34 (5) ◽  
pp. 431 ◽  
Author(s):  
Behjat Kosar-Hashemi ◽  
Zhongyi Li ◽  
Oscar Larroque ◽  
Ahmed Regina ◽  
Makoto Yamamori ◽  
...  
Keyword(s):  
Triticum Aestivum L ◽  
Endosperm Development ◽  
Starch Synthase ◽  
Starch Granules ◽  
Branching Enzyme ◽  
Wild Type ◽  
Drastic Reduction ◽  
Branching Patterns ◽  
Soluble Phase ◽  
Mutant Lines

A line of wheat (Triticum aestivum L.), sgp-1, that does not express starch synthase II (SSII, also known as SGP-1) has previously been reported. In this study, F1 derived doubled haploid lines with homozygous wild type or mutant alleles for SGP-1 genes were identified from a cross between the original mutant and a wild type Australian cultivar. Analysis of the starch granules showed that in the mutant lines they are markedly distorted from 15 days postanthesis during grain development. Starch branching patterns showed an increase in the proportion of short chains (DP 6–10) at an earlier stage, but this increase became much more pronounced at 15 days postanthesis and persisted until maturity. There was also a consistent and drastic reduction throughout seed development in the relative amounts of starch branching enzyme II (SBEII, comprising SBEIIa and SBEIIb) and starch synthase I (SSI) bound to the starch granules. In the soluble phase, however, there was relatively little change in the amount of SBEIIb, SBEIIa or SSI protein. Therefore loss of SSII specifically leads to the loss of SBEIIb, SBEIIa and SSI protein in the granule-bound phase and the effect of this mutation is clearly manifest from the mid-stage of endosperm development in wheat.

Study of kernel structure of high-amylose and wild-type rice by X-ray microtomography and SEM

2012 ◽  
Vol 55 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Li-Jia Zhu ◽  
Hulya Dogan ◽  
Hyma Gajula ◽  
Ming-Hong Gu ◽  
Qiao-Quan Liu ◽  
...  
Keyword(s):  
Wild Type ◽  
X Ray ◽  
High Amylose

scholarly journals Localization of a bacterial protein in starch granules of transgenic maize kernels

2003 ◽  
Vol 100 (19) ◽  
pp. 11127-11132 ◽  
Author(s):  
R. K. Chikwamba ◽  
M. P. Scott ◽  
L. B. Mejia ◽  
H. S. Mason ◽  
K. Wang
Keyword(s):  
Transgenic Maize ◽  
Starch Granules ◽  
Bacterial Protein ◽  
Maize Kernels

scholarly journals PAC1, a pH-Regulatory Gene from Fusarium verticillioides

2003 ◽  
Vol 69 (9) ◽  
pp. 5222-5227 ◽  
Author(s):  
Joseph E. Flaherty ◽  
Anna Maria Pirttilä ◽  
Burton H. Bluhm ◽  
Charles P. Woloshuk
Keyword(s):  
Fusarium Verticillioides ◽  
Regulatory Gene ◽  
Synthetic Medium ◽  
Transcriptional Regulators ◽  
Acidic Ph ◽  
Alkaline Ph ◽  
Wild Type ◽  
Ph Responsive ◽  
Alkaline Conditions ◽  
Maize Kernels

ABSTRACT Fumonisins are a group of mycotoxins that contaminate maize and cause leukoencephalomalacia in equine, pulmonary edema in swine, and promote cancer in mice. Fumonisin biosynthesis in Fusarium verticillioides is repressed by nitrogen and alkaline pH. We cloned a PACC-like gene (PAC1) from F. verticillioides. PACC genes encode the major transcriptional regulators of several pH-responsive pathways in other filamentous fungi. In Northern blot analyses, a PAC1 probe hybridized to a 2.2-kb transcript present in F. verticillioides grown at alkaline pH. A mutant of F. verticillioides with a disrupted PAC1 gene had severely impaired growth at alkaline pH. The mutant produced more fumonisin than the wild type when grown on maize kernels and in a synthetic medium buffered at an acidic pH, 4.5. The mutant, but not the wild type, also produced fumonisin B1 when mycelia were resuspended in medium buffered at an alkaline pH, 8.4. Transcription of FUM1, a gene involved in fumonisin biosynthesis, was correlated with fumonisin production. We conclude that PAC1 is required for growth at alkaline pH and that Pac1 may have a role as a repressor of fumonisin biosynthesis under alkaline conditions.

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