Category: Biotechnology

Scientists a step closer to developing disease resistant maize variety

Scientists at International Maize and Wheat Improvement Center (CIMMYT) at Hyderabad, India in collaboration with their counterparts in Nairobi, Kenya have conducted a genome-wide association study (GWAS) to identify regions in maize DNA that confer improved resistance to sorghum downy mildew disease in maize. SDM is an important foliar disease of maize caused by the fungus, Peronosclerospora sorghi.

We all relish corn- be it as popcorn, sweet corn or the breakfast staple- corn flakes. Maize or the Corn is the world’s leading cereal grain with a total production that has surpassed wheat or rice and India is one of the eight major maize growing countries in Asia. Unfortunately, during the monsoon season, the total productivity is limited due to the susceptibility to a number of diseases like downy mildews (DM), leaf blights, rusts, stalk rots and ear rots with DM spread throughout Asia.

In this report, the group conducted a genome-wide association study (GWAS) for sorghum downy mildew (SDM) resistance in a panel of 368 inbred lines adapted to the Asian tropics. Along with previously reported regions conferring resistance to SDM, they identified novel SNPs in the genome that are important. SNPs or Single Nucleotide Polymorphism is a variation in a single nucleotide (basic unit of the DNA) that occurs at a specific location in the genetic code and each change or variation is present to some degree within a population.

Six of these SNPs belong to significant regions reported to be associated with DM resistance and could be useful in maize breeding programs to develop DM-resistant maize varieties. The study was led by Dr. Sudha K Nair, Senior Molecular Geneticist, CIMMYT, Hyderabad.

“Downy mildew being a devastating problem for the entire Asian maize cultivation, understanding the genetics of the trait, and using that in breeding for resistant varieties is the most ecologically efficient way of managing the disease. It is for the first time that, a panel of about 400 maize inbred lines is being used in a genome-wide association study using high density, genome-wide SNP markers of more than 300,000 for identifying genomic regions responsible for the quantitative resistance towards downy mildew in maize”, explained Dr. Nair.

Metalaxyl, a chemical that is used to kill the fungus causing DM, is less effective now as the fungus has developed resistance to it owing to its extensive use. Thus, rather than using chemicals, farmers need a more sustainable and less expensive alternative to combat SDM in maize.

“On the basis of Genome wide association (GWAS), significant number of SNPs and haplotypes observed in Asiatic tropical maize breeding lines wherein eight novel genomic regions associated with Sorghum Downy Mildew (SDM) resistance were reported for the first time in the present study. In addition, ten marker-phenotypic trait associations identified were co-located within the genes associated with SDM resistance that could provide critical information for future empirical studies for improvement of breeding programs in maize”, explained Dr. Vishal Acharya, Scientist, Functional Genomics and Complex System Lab at CSIR-Institute of Himalayan Bioresource Technology, Palampur. Dr. Acharya is not connected with the study.

Dr. Nair and her team is quite hopeful, “We are in the process of validating the resistance-associated SNP markers in our maize breeding program, which could then be shared with all our partners, both public and private, for routine use in maize breeding programs in the region”.

“The International Maize and Wheat Improvement Center, known by its Spanish acronym, CIMMYT®, is one of the 15 independent, international, non-profit agricultural research organizations that make up the CGIAR (Consultative group on International Agricultural Research) with partners in over 100 countries (www.cimmyt.org). Head-quartered in Mexico, Hyderabad is the hub for CIMMYT’s tropical maize improvement activities for Asia”, Dr. S K Nair added.

The team comprised of Zerka Rashid, Pradeep Kumar Singh, Hindu Vemuri, Pervez Haider Zaidi, and Sudha Krishnan Nair from CIMMYT, Hyderabad and Boddupalli Maruthi Prasanna, Program Director, Global Maize Program from CIMMYT, Nairobi. The study was published in journal Scientific Reports.

Featured Image Courtesy: www.pexels.com

New method developed to prepare milk protein-vitamin A complexes

Low-fat and fat-free foods are gaining popularity lately. Although restricting the amount of fat in the diet is good for health, paradoxically, it also results in loss of fat soluble vitamins and essential fatty acids leading to a myriad of deficiencies. The challenge then becomes the addition of fat soluble nutrients to such fat-free or low-fat foods to make up for these deficiencies.

Scientists at the National Dairy Research Institute (NDRI), Karnal, Haryana have come up with a method to enhance the nutritional content of fat-free milk by preparing Vitamin-A and Milk Protein complexes.

Vitamin-A is one of the four fat-soluble essential vitamins, the others being D, E and K. The deficiency of Vitamin-A, which is the leading cause of preventable childhood blindness is a major public health problem in India.

Dr. Arora and his team of researchers modified casein, the major protein present in milk, with a chemical called succinic anhydride (SA) and prepared succinylated casein- Vit A complexes. They tried different combinations and found sodium caseinate-Vit A and succinylated sodium caseinate-Vit A complexes had high Vitamin-A binding ability and solubility.

SA is classified under the ‘generally recognized as safe (GRAS)’ category by the United States Food and Drug Administration (USFDA) thus modifications of casein using SA are considered safe for human consumption.

They suggest that casein owing to its unique properties can be easily used as a delivery vehicle for Vitamin-A in milk.

 

“FSSAI (Food Safety and Standards Authority of India) has approved the addition of vitamins A and D to milk. These vitamins are being used for fortifying milk by Mother Dairy, Amul and many state cooperatives at the moment”, Dr. Arora commented. He further added, “addition of minerals would be the next step”. He assures us that such fortified foods are no longer a fantasy and that these improvements will be done incrementally.

 

Such strategies involving the fortification of staple foods like milk, rice, salt, etc. are the most important tools in India’s arsenal for the fight against malnutrition.

The team led by Dr. Sumit Arora included Chitra Gupta, M.A. Syama and Apurva Sharma at the Dairy Chemistry Division, National Dairy Research Institute (NDRI), Karnal, Haryana. This work was published in the journal Food Chemistry and was financially supported by Department of Biotechnology (DBT), Government of India.

Hanging drop – the new 3-D culture

The Human Body is a complex interplay of different organs with specialized functions. These organs are very well integrated, working together towards one goal- the sustenance of life. Scientists have been working for ages trying to understand the normal functioning of the human body, yet there is so little that we know.

The liver is a vital organ of the animal body. Among its varied physiologic roles; detoxification, metabolism, and the secretion of plasma proteins are some of the important functions. Most of the liver is made up of cells called the hepatocytes and these cells are responsible for majority of its functions. Thus, to further understand the physiological functions, the diseased state or response of liver to drugs/toxins, scientists need to study at the level of the functional unit-the hepatocyte. It has always been a quest for researchers to understand the human biology in systems as close as possible to themselves. Before engaging animal models, such studies are done in a 2-dimensional culture system (2-D) of hepatocytes either derived from humans or immortalized cell lines. Both the systems have their own benefits and drawbacks that need to be taken care of.

Among the many, one limitation of 2-D culturing of cell lines is that the immortalized cells are present as monolayers like sheets, which is very different from their organization inside our body. In the body (or organ) they are like balls in a bag, they touch, talk and efficiently work with each other. Thus the 2-D system fails to represent the human organ closely.

The other approach is the use of 3-dimensional culture systems. Scientists have tried different substrates or surfaces like extracellular matrix (ECM) sandwiching, ECM hydrogels, alginate sponges, self-assembly peptide fibers, electrospun fibers, 3D printed scaffolds and spheroid cultures for 3-D culturing of cells. For varied reasons, like organization or poor mechanical properties or cost, to name a few, most of these systems cannot be routinely used except for spheroid cultures.

S K Onteru and coworkers at the National Dairy Institute, Karnal, (Onteru 2017) have tried to establish a 3-D spheroids culture system of hepatocytes that mimics the human liver more closely as compared to the available 2-D arrangement. They took cells from sheep and buffalo livers from slaughterhouses and cultured them in varying media and culture conditions and showed that in one of the conditions called Hanging Drop method with a special medium called Williams medium, the cells were very similar in their organization and gene make up as the freshly derived liver cells. In this method, there were no substrates onto which the cells adhered, the cells formed micro tissues under the gravitational force in the absence of any synthetic materials.

Blog pic 1

Cells in the hanging drop are more like the cells in our body. The DNA and protein analysis of human and cattle studies revealed a close resemblance between the two. The liver of humans, cattle, sheep and goat have also been shown to be very similar in structure, which makes it relevant to study human liver functions and response to drugs in these systems apart from small rodents like mice. Onteru’s group shows that the sheep and buffalo cells can be maintained in such spherical hanging drops for 12 and 6 days respectively before they start losing the 3-D structure.

Although the results seem to be promising, a lot of hurdles need to be crossed. The overall viability of these cells was only 33% (sheep cells) and 20% (buffalo cells). They suggest that this can be improved by a reduction in the contamination and more defined sample collection procedures.

In Dr. Onteru’s opinion, “Particularly, selecting the liver samples from healthy young animals of less than two years old without any pathologies and infections would be beneficial for the success of this culture system”.

A new culturing system that is less expensive and closer to the human organ is proposed but a lot of obstacles need to be overcome before this system can be routinely used in the laboratory as a substitute to human derived primary cells or small animal models.

Dr. Dheer Singh (team leader and co-author) states, “Currently, the culture systems are being used for toxicology studies. If these studies are successful, we can use this system routinely in laboratories within 4-5 years”. 

These results are published in April 2017 issue of Scientific Reports, a Nature research journal and can be accessed at Onteru 2017.