What makes brown rice healthy? Decoding the chemistry of its nutritional wealth
Researchers have found that the ester compound cycloartenyl ferulate is chiefly responsible for the health-promoting effects of brown rice
Peer-Reviewed PublicationIMAGE: SEVERAL FAT-SOLUBLE COMPOUNDS PRESENT IN BROWN RICE HAVE ANTIOXIDANT CAPACITY BUT ARE PRESENT IN SMALL QUANTITIES. CYCLOARTENYL FERULATE, A RELATIVELY ABUNDANT MOLECULE, HAS BEEN REVEALED AS THE MAJOR COMPOUND RESPONSIBLE FOR SEVERAL HEALTH BENEFITS OF BROWN RICE. view more
CREDIT: YOSHIMASA NAKAMURA
Asian diets feature rice as a staple grain, contributing towards nearly 90% of the world’s rice consumption. Brown rice, in particular, is known to have several health benefits. As a regular addition to the diet, it can help reduce body weight, lower cholesterol, and suppress inflammation. The ability of brown rice to neutralize reactive oxygen species and prevent cellular damage is vital to many of its health-promoting effects. Although previous studies have shown that the antioxidant compounds in brown rice can protect cells against oxidative stress, knowledge regarding which major compound contributes towards these beneficial properties has long remained a mystery.
In a recent study led by Professor Yoshimasa Nakamura from the Graduate School of Environmental and Life Science, Okayama University, researchers from Japan have identified cycloartenyl ferulate (CAF) as the main “cytoprotective” or cell-protecting compound in brown rice. CAF is a unique compound owing to its hybrid structure. As Professor Nakamura explains, “CAF is a hybrid compound of polyphenol and phytosterol and is expected to be a potent bioactive substance with various pharmacological properties, such as antioxidant effect and blood fat-lowering effect.”
The study published on January 3, 2023 in volume 24 issue 1 of International Journal of Molecular Sciences, was co-authored by Hongyan Wu, from Dalian Polytechnic University, and Toshiyuki Nakamura, from the Graduate School of Environmental and Life Science at Okayama University. In it, the researchers provide evidence of CAF’s antioxidant properties by demonstrating that it can protect cells from stress caused by hydrogen peroxide. Although hydrogen peroxide is a by-product of a cell’s metabolic processes, abnormal amounts of the compound can be toxic to cells and cause irreversible damage. Treatment of cells with CAF increased their resistance to toxic stress induced by hydrogen peroxide. Moreover, CAF provided greater protection from hydrogen peroxide-induced stress compared to alpha-tocopherol and gamma-tocopherol, two other prominent antioxidant compounds that were earlier speculated to be major contributors to the antioxidant capacity of brown rice.
According to the study’s estimates, the amount of CAF in the whole grain of brown rice is five-fold higher than that of other antioxidant compounds found in brown rice. Further, CAF increases the concentration of heme oxygenase-1 or HO-1, an enzyme that facilitates the production of antioxidants. “We demonstrated here that CAF significantly increased the mRNA level of HO-1, the small molecular weight antioxidant-producing enzyme, at concentrations similar to that required for cytoprotective effects in resistance to oxidative damage,” Professor Nakamura explains.
The researchers further explored this mechanism of action through experiments where blocking HO-1 activity using inhibitors reduced the antioxidant effect of CAF considerably. The high abundance and unique mechanism of action are evidence that CAF is the major contributing antioxidant in brown rice.
Through this study, the researchers have not only uncovered the secret to the health benefits of brown rice, but also locked down on the component that is majorly responsible for these benefits. This will allow the use of CAF in the development of better novel supplements and food products focused on consumer health. As an optimistic Professor Nakamura observes, “Our study can help in the development of new functional foods and supplements based on the functionality of CAFs, like CAF-based nutraceuticals.”
Although, with such naturally occurring health benefits, brown rice still very much looks to be on the menu!
About Okayama University, Japan
As one of the leading universities in Japan, Okayama University aims to create and establish a new paradigm for the sustainable development of the world. Okayama University offers a wide range of academic fields, which become the basis of the integrated graduate schools. This not only allows us to conduct the most advanced and up-to-date research, but also provides an enriching educational experience.
Website: https://www.okayama-u.ac.jp/index_e.html
About Professor Yoshimasa Nakamura from Okayama University, Japan
Dr Yoshimasa Nakamura is a professor at the Graduate School of Environmental and Life Science at Okayama University. He has nearly 30 years of research experience and has published over 317 scientific articles. His fields of academic interest include Phytochemicals, Reactive Oxygen Species and Antioxidants, Lipid Peroxidation, Apoptosis, Cell Apoptosis and GSH. Professor Nakamura has previously worked at Kyoto University, Nagoya University, and University of Illinois at Chicago.
JOURNAL
International Journal of Molecular Sciences
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Cells
ARTICLE TITLE
Cycloartenyl ferulate is the predominant compound in brown rice conferring cytoprotective potential against oxidative stress-induced cytotoxicity
Rice breeding breakthrough to feed billions
IMAGE: IMTIYAZ KHANDAY AND VENKATESAN SUNDARESAN PHOTOGRAPHED WITH CLONED RICE PLANTS IN A GREEN HOUSE ON THE UC DAVIS CAMPUS. THEIR WORK HAS LED TO A BREAKTHROUGH IN APOMIXIS, PROPAGATING A HYBRID RICE VARIETY AS CLONAL SEEDS. view more
CREDIT: KARIN HIGGINS/UC DAVIS
An international team has succeeded in propagating a commercial hybrid rice strain as a clone through seeds with 95 percent efficiency. This could lower the cost of hybrid rice seed, making high-yielding, disease resistant rice strains available to low-income farmers worldwide. The work was published Dec. 27 in Nature Communications.
First-generation hybrids of crop plants often show higher performance than their parent strains, a phenomenon called hybrid vigor. But this does not persist if the hybrids are bred together for a second generation. So when farmers want to use high-performing hybrid plant varieties, they need to purchase new seed each season.
Rice, the staple crop for half the world’s population, is relatively costly to breed as a hybrid for a yield improvement of about 10 percent. This means that the benefits of rice hybrids have yet to reach many of the world’s farmers, said Gurdev Khush, adjunct professor emeritus in the Department of Plant Sciences at the University of California, Davis. Working at the International Rice Research Institute from 1967 until retiring to UC Davis in 2002, Khush led efforts to create new rice high-yield rice varieties, work for which he received the World Food Prize in 1996.
One solution to this would be to propagate hybrids as clones that would remain identical from generation to generation without further breeding. Many wild plants can produce seeds that are clones of themselves, a process called apomixis.
“Once you have the hybrid, if you can induce apomixis, then you can plant it every year,” Khush said.
However, transferring apomixis to a major crop plant has proved difficult to achieve.
One Step to Cloned Hybrid Seeds
In 2019, a team led by Professor Venkatesan Sundaresan and Assistant Professor Imtiyaz Khanday at the UC Davis Departments of Plant Biology and Plant Sciences achieved apomixis in rice plants, with about 30 percent of seeds being clones.
Sundaresan, Khanday and colleagues in France, Germany and Ghana have now achieved a clonal efficiency of 95 percent, using a commercial hybrid rice strain, and shown that the process could be sustained for at least three generations.
The single-step process involves modifying three genes called MiMe which cause the plant to switch from meioisis, the process that plants use to form egg cells, to mitosis, in which a cell divides into two copies of itself. Another gene modification induces apomixis. The result is a seed that can grow into a plant genetically identical to its parent.
The method would allow seed companies to produce hybrid seeds more rapidly and at larger scale, as well as providing seed that farmers could save and replant from season to season, Khush said.
“Apomixis in crop plants has been the target of worldwide research for over 30 years, because it can make hybrid seed production can become accessible to everyone,” Sundaresan said. “The resulting increase in yields can help meet global needs of an increasing population without having to increase use of land, water and fertilizers to unsustainable levels.”
The results could be applied to other food crops, Sundaresan said. In particular, rice is a genetic model for other cereal crops including maize and wheat, that together constitute major food staples for the world.
Khush recalled that he organized a 1994 conference on apomixis in rice breeding. When he returned to UC Davis in 2002, he gave a copy of the conference proceedings to Sundaresan.
“It’s been a long project,” he said.
Coauthors on the paper are: Aurore Vernet, Donaldo Meynard, Delphine Meulet, Olivier Gibert, Ronan Rivallan, Anne Cecilé Meunier, Julien Frouin, James Tallebois, Daphné Autran, Olivier Leblanc and Emmanuel Guiderdoni, CIRAD and University of Montpellier, France; Qichao Lian and Raphael Mercier, Max Planck Institute for Plant Breeding Research, Cologne, Germany; Matilda Bissah, CSIR Plant Genetics Resources Research Institute, Ghana; and Kyle Shankle, UC Davis. Khush is not an author on the new paper.
The work was supported in part by funding from the Innovative Genomics Institute and the France-Berkeley Fund.
JOURNAL
Nature Communications
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
High-frequency synthetic apomixis in hybrid rice
COI STATEMENT
INRAE, the former employer of author R.M., holds patents on MiMe and its use to engineer apomixis. A provisional application for an US patent has been filed on October 3rd 2022 (# 63/412,667) by UC Davis, CIRAD and MPIPZ, with I.K., V.S., E.G., De.M., and R.M. as inventors. The remaining authors declare no competing interests.
Researchers uncover key codon repeats regulating chilling tolerance in rice
IMAGE: SCHEMATIC REPRESENTATION DEMONSTRATING DOMESTICATION-SELECTED COLD11 MODULES FOR REPAIRING DNA DOUBLE-STRAND BREAK INDUCED BY CHILLING IN RICE. view more
CREDIT: PROF. CHONG KANG'S GROUP
A recent study by Prof. CHONG Kang's group from the Institute of Botany of the Chinese Academy of Sciences (CAS) has revealed a novel cold domesticated repair mechanism for DNA damage in rice, providing corresponding elite modules for the improvement of chilling tolerance trait in rice with the codon repeats at a single site.
Results were published online in Science Advances.
Global climate change has led to a clear increase in abnormal environmental temperatures and extreme weather events in recent years. Thus, it is urgent that crops have the capacity to endure extreme temperatures in order to ensure stable yields. Although plants have evolved complicated and delicate protective mechanisms to survive chilling stress, DNA damage still occurs, thus lowering plants' defenses. Furthermore, the underlying regulatory mechanism has been largely unclear.
In this study, Prof. CHONG's group, in cooperation with Prof. LI Qizhai's group from the Academy of Mathematics and Systems Science of CAS, and Prof. CHENG Zhukuan's group from the Institute of Genetics and Developmental Biology of CAS, used an approach that combines population genetics, genomics, and cell and evolutionary biology to exploit the novel module for chilling tolerance.
The researchers performed data-merging genome-wide association studies (DM-GWAS) based on multidimensional scaling. A series of loci were identified by GWAS using merged phenotypic data. One of these was qCTS11-1 on chromosome 11, which makes a clear contribution to rice chilling tolerance. Its major gene, COLD11, was identified with fine-scale mapping. Loss-of-function mutations of COLD11 caused reduced chilling tolerance, according to the researchers.
Different types of GCG codon repeats encoding alanine in the first exon of COLD11 were observed for chilling-sensitive indica varieties and chilling-tolerant japonica varieties. The GCG codon repeat numbers had a clear, positive correlation with chilling tolerance. In addition, genome evolution analysis of representative rice germplasms suggested that numerous GCG sequence repeats were subjected to strong domestication selection during the northern expansion of rice planting.
Furthermore, COLD11 encodes a DNA repair protein that plays an essential role in the repair of DNA double-strand breaks. The GCG repeat numbers in its first exon showed a positive correlation with its biochemical activity. This is the first report of a domestication-selected DNA damage repair mechanism and its corresponding elite modules involving chilling stress.
Using DM-GWAS of japonica and indica—two rice subspecies with substantial divergence in chilling tolerance—this study reveals that COLD11 is a major quantitative trait loci gene for chilling tolerance.
The discovery of the key codon repeats in the first exon of COLD11, confirmed by phylogenetic and geographic distribution analysis, opens the way for fine regulation of rice chilling tolerance with a single site. It is a potentially useful molecular module for improving the chilling tolerance trait in rice through molecular design.
JOURNAL
Science Advances
METHOD OF RESEARCH
Meta-analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Natural variation of codon repeats in COLD11 endows rice with chilling resilience
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