Transgenic Biofortification of the Starchy Staple Cassava (Manihot esculenta) Generates a Novel Sink for Protein

Abhary, Mohammad; Siritunga, Dimuth; Stevens, Gene; Taylor, Nigel J.; Fauquet, Claude

doi:10.1371/journal.pone.0016256

Cited by 17 publications

(23 citation statements)

References 24 publications

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“…Importantly, the linamarin content of wild-type (cultivar TMS-60444) leaves was similar to those previously reported for other cassava cultivars [reviewed in 7, 15]. In contrast, the leaf linamarin levels reported for the identical cultivar (TMS-60444) using the cyanide-electrode assay system averaged 3.7 µmole/gdw (100 ppm) or 10 fold lower than the measurements made by GC-MS [27]. Finally, in contrast to the HNL overexpressing plants, transgenic plants overexpressing zeolin in storage roots had an apparent 50% reduction in reported leaf linamarin levels [27].…”

Section: Resultssupporting

confidence: 84%

Overexpression of Hydroxynitrile Lyase in Cassava Roots Elevates Protein and Free Amino Acids while Reducing Residual Cyanogen Levels

et al. 2011

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Cassava is the major source of calories for more than 250 million Sub-Saharan Africans, however, it has the lowest protein-to-energy ratio of any major staple food crop in the world. A cassava-based diet provides less than 30% of the minimum daily requirement for protein. Moreover, both leaves and roots contain potentially toxic levels of cyanogenic glucosides. The major cyanogen in cassava is linamarin which is stored in the vacuole. Upon tissue disruption linamarin is deglycosylated by the apolplastic enzyme, linamarase, producing acetone cyanohydrin. Acetone cyanohydrin can spontaneously decompose at pHs >5.0 or temperatures >35°C, or is enzymatically broken down by hydroxynitrile lyase (HNL) to produce acetone and free cyanide which is then volatilized. Unlike leaves, cassava roots have little HNL activity. The lack of HNL activity in roots is associated with the accumulation of potentially toxic levels of acetone cyanohydrin in poorly processed roots. We hypothesized that the over-expression of HNL in cassava roots under the control of a root-specific, patatin promoter would not only accelerate cyanogenesis during food processing, resulting in a safer food product, but lead to increased root protein levels since HNL is sequestered in the cell wall. Transgenic lines expressing a patatin-driven HNL gene construct exhibited a 2–20 fold increase in relative HNL mRNA levels in roots when compared with wild type resulting in a threefold increase in total root protein in 7 month old plants. After food processing, HNL overexpressing lines had substantially reduced acetone cyanohydrin and cyanide levels in roots relative to wild-type roots. Furthermore, steady state linamarin levels in intact tissues were reduced by 80% in transgenic cassava roots. These results suggest that enhanced linamarin metabolism contributed to the elevated root protein levels.

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Section: Resultssupporting

confidence: 84%

Overexpression of Hydroxynitrile Lyase in Cassava Roots Elevates Protein and Free Amino Acids while Reducing Residual Cyanogen Levels

et al. 2011

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“…One major aim of The BioCassava Plus Program (Sayre et al, 2011) is the accumulation of storage proteins with known amino acid profiles in tuberous roots, thus transforming cassava to a primary calorie source that supplies a nutritionally balanced storage protein. In addition to the complexity of cassava breeding, no significant variability in protein content exists in cassava germplasm (Abhary et al, 2011). Thus, conventional crop improvement methods are not viable for this type of nutritional improvement in cassava (Abhary et al, 2011).…”

Section: Protein Modificationmentioning

confidence: 99%

“…In addition to the complexity of cassava breeding, no significant variability in protein content exists in cassava germplasm (Abhary et al, 2011). Thus, conventional crop improvement methods are not viable for this type of nutritional improvement in cassava (Abhary et al, 2011).…”

Section: Protein Modificationmentioning

confidence: 99%

“…Another advantage introduced by HNL overexpression in cassava roots was the accelerated conversion of acetone cyanohydrin to volatile cyanide, leading to the reduced potential toxicity of cassava foods (Siritunga and Sayre, 2004;Sayre et al, 2011). A second approach towards the same objective was the expression of a chimeric storage protein (zeolin) in cassava roots (Abhary et al, 2011). The chimeric protein combines phaseolin from common bean (Phaseolus vulgaris) and gamma zein from maize (Zea mays) and was shown to make protein bodies in the endoplasmic reticulum.…”

Section: Protein Modificationmentioning

confidence: 99%

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Biotechnology for Enhanced Nutritional Quality in Plants

Uncu¹,

Doğanlar²,

Frary³

2013

Critical Reviews in Plant Sciences

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“…Zeolin is a fusion product between phaseolin, the major storage protein in common beans (Phaseolus vulgaris), and a truncated gamma-zein protein from maize (Zea mays), which directs the fused polypeptide to form stable protein bodies within the ER (Mainieri et al (2004). According to Abhary et al (2011), the production of transgenic cassava plants expressing zeolin had storage roots with up to 12.5% of DW as protein, a more than fourfold increase compared to controls with no associated accumulation of protein in leaf tissues. Analysis of transgenic plants grown under greenhouse and field conditions have confirmed that this trait is stable when plants are propagated vegetatively; that it does not impact plant development, and that it is correlated with a significant reduction in the cyanogen content of both leaf and root tissues.…”

Section: Protein Content Of Cassava Roots For Nutritional Enhancementmentioning

confidence: 99%

Cassava Genetic Improvement

Ceballos¹,

Fregene²,

Carlos³

et al. 2007

Breeding Major Food Staples

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PREFACEThis Handbook is the result of a combined effort by several current and previous cassava researchers at CIAT to review and summarize the most important results of cassava research during the past 40 years. Most of the chapters are based on the various presentations during the Regional Cassava Training Course, held in Thailand from October 6 to 17, 2008. This course was organized upon the realization that many people that were actively involved with cassava research in the 1970s and 80s, both at CIAT and in national programs, have now retired or will soon do so, and that a whole new generation of cassava researchers are currently being hired to take their place.As cassava is now becoming a very important, and mostly industrial, crop in Asia, there are many new opportunities, but also a host of new problems and challenges. These include the appearance in Asia of new cassava diseases and pests; the decreasing availability and increasing cost of rural labor, resulting in the need for partial or complete mechanization of cassava production; the rapidly increasing demand for cassava roots for production of food, feed and fuel, and the unavailability in many countries of new land for any expansion of cassava area, thus requiring a rapid increase in cassava yields to increase supplies. This requires a renewed focus on cassava research for the development of new higher-yielding varieties and more sustainable production practices.While many cassava researchers in national programs in Asia received individual or group training at CIAT-Colombia during the 1970s and 80s, this training was greatly reduced during the following two decades due to funding limitations. Thus, the objective of the Regional Cassava Training Course in 2008 was to provide a new training opportunity for young scientists in Asian countries, and to hand over the knowledge and experience of the older cassava researchers, mostly from CIAT, to a new generation that will have to face the new challenges. Thus, the course was taught mostly by current or already retired CIAT cassava researchers, while the 60-plus participants of the course included cassava researchers from Cambodia, China, East Timor, India, Indonesia, Lao PDR, Malaysia, Myanmar, the Philippines, Thailand and Vietnam. The training course not only provided knowledge -from physiology and biotechnology to animal feeding and production of fuelethanol -but also an opportunity for people from different institutions and countries to get to know each other, which will greatly facilitate future collaboration.Course participants returned home with a CD containing the PowerPoint presentations of the course. However, it was felt that a more comprehensive review of all the topics covered was warranted, as this would provide more in-depth knowledge for those working in the various specialized fields. Most of this information is available in many refereed journals, in workshop proceedings and old CIAT annual reports, but many of these are now out of print or otherwise difficult to obtain. Thus, the Cas...

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Transgenic Biofortification of the Starchy Staple Cassava (Manihot esculenta) Generates a Novel Sink for Protein

Cited by 17 publications

References 24 publications

Overexpression of Hydroxynitrile Lyase in Cassava Roots Elevates Protein and Free Amino Acids while Reducing Residual Cyanogen Levels

Overexpression of Hydroxynitrile Lyase in Cassava Roots Elevates Protein and Free Amino Acids while Reducing Residual Cyanogen Levels

Biotechnology for Enhanced Nutritional Quality in Plants

Cassava Genetic Improvement

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