Agricultural Biotechnology

  

ABSTRACT
In the current situation, the most pressing concern facing humanity is ensuring food security for an expanding population. Unfavorable weather, limited fertile and cultivation land, and increased environmental pressures, in addition to the expanding population rate, are key restraints for  cultivation and food supply. With the progress in Plant Biotechnology, it is becoming easy to control these challenges and increase crop production. It has made it possible to breed for almost any desired trait. Molecular biologists can now work on obtaining desired trait and knocking out the undesired trait gene, thanks to advances in Plant Biotechnology.

OUTLINE
This article will emphasis on the plant biotechnology tools used for crop improvements.  

INTRODUCTION
Agricultural Biotechnology refers to the techniques used to introduce specific desirable traits into plants, animals and microorganisms. By the virtues of Agricultural Biotechnology, the plants growth and productivity has been enhanced by introducing resistance genes to deal with several  environmental stresses and pathogens attack to deal with plant diseases. In this paper, I am focusing on how Plant Biotechnology is used to improve crop production.  

Plant Biotechnology is a set of techniques used to introduce desired traits or eliminating the undesired traits from plants. Recombinant DNA  technology has aided plant breeders in meeting the increased food demand expected for the twenty-first century, and it holds tremendous potential for the twenty-first century.  

CHALLENGES IN PLANT GROWTH AND PRODUCTIVITY
The growth, survival and productivity of plants is greatly affected by biotic and abiotic factors. Breeding has become difficult in many plant species due to the lack of sufficient resistance genes.
In addition, different plant pathogens (bacteria, viruses and fungi) attack plants causing decline in growth and productivity of plants. 

CHALLENGES IN CROP IMPROVEMENT
Rapid population increase, climate variability, and environmental problems are just a few of the major challenges that have posed a threat to global food security. It is important to improve agricultural productivity in order to achieve food and nutrition security. As a result, producing high-yielding, disease-resistant, and climate-resilient crops is critical for increasing crop
productivity. Conventional breeding methods like as hybridization and mutant breeding have played an important role in enhancing crop productivity for many years. But due to decreased diversity in naturally occurring plants has led to decline in the production of newer varieties. GM- crops were thought to be a solution to overcome food shortage and improved crop production but it is labor- intensive and consumes a lot of time to produce a new variety. Further, GM-crops are not readily accepted by some people due to several insecurities.

TECHNIQUES USED TO IMPROVE PLANTS
The techniques we use in Plant Biotechnology includes:

• Gene Transfer
• Use of Vectors such as Plasmids
• Use of Enzymes (Restriction enzyme and DNA Ligase)
• Cloning
• PCR
• Tissue Culturing     

The conventional/traditional breeding techniques are confined to the exchange of genes within a certain number of crop species. By combining conventional techniques with Biotechnological techniques, the quality of the plants can be improved significantly. Biotechnology has made it easy to more targeted delivery of the desired trait into the crop plant. Further, a variety of genes can be introduced into the crop plants which is not possible with conventional breeding alone. The gene transfer can be intra-species or even across kingdoms. For example, in order to induce pathogen resistance gene in crop plants, a gene of the bacterium Bacillus thuringiensis is incorporated into crop plant e.g., Bt-maize (Birhanu Babiye, Girma Haile, Mulugeta Adamu, 2020).

PLANT BIOTECHNOLOGY TOOLS
The genome-editing tools in Plant Biotechnology are given below
a) Zinc-Finger Nucleases (ZFNs)
b) Transcription Activator-Like Effector Nucleases (TALENs)
c) Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) 

ZFN is used in Plant Biotechnology to alter the genome. It is an artificial enzyme. It targets specific sequence of DNA within the genome. It consists of: 
• ZF DNA-binding domain
• ZF DNA-cleavage domain (endonuclease)

Four types of outcomes are possible when it comes to DNA modifications. It depends on donor molecule’s type and presence. In Gene Targeting, a donor is present having flanking homology at double-strand break site and is utilizing HDR. In this case, the genes present between the flanking homology are inserted into the genome. In Gene Editing, like that of Gene Targeting, a donor is present having flanking homology at double-strand break site and is utilizing HDR. But in this case, the mutations are edited instead of adding additional genetic material. In NHEJ Gene Addition, there is absence of flanking homology in donor DNA and the NHEJ repairing doe not work well. In this case, the donor’s genes are inserted into the double strand break site. In Gene Mutagenesis, no donor DNA is present and the NHEJ cannot repair double strand break properly (Novak, 2018). 

TALENs is another endonuclease which is used to improve plants. In-silico tools are available to design and study them. TALEN is more precise than ZFN. It is similar to ZFN in that it also contains FokI attached to DNA binding domain which creates DNA cleavage. This double-strand breakdown/cleavage is repaired either by NHEJ or HDR. HDR is more precise as compared to NHEJ. In HDR, the homologous sequence is used as a template to repair the DNA cleavage while in NHEJ, there is no template and the DNA is repaired by insertion- deletion which may cause
errors. TALEN is successfully being used for gene silencing, gene inactivation, deletion and gene disruption. It is highly specific to the target suggesting their use as a potential tool for crop improvements in plants. It has been used for agriculturally important crops like wheat, rice, barley,
tomatoes etc. They are easy to assemble, reliable in their function, and target- specificity.

n CRISPR/Cas9, first the protospacer adjacent motif is identified. Next, there a complementary sgRNA synthesized which binds to the specific site in targeted gene. A binary vector is used to used to clone sgRNA. Then it is delivered into host system by different ways, some of which include floral dips, the use of biolistic guns, micro-injection etc. the transgenic species are then screened via Sanger Sequencing, Real Time PCR, etc. Finally, the transgenic crop plants are evaluated for different challenges including stress tolerance etc. (Deepa Jaganathan, Karthikeyan Ramasamy, Gthandapani Sellamuthu, Shilpa Jayabalan, and Gayatri Venkataraman, 2018). 

CONCLUSION
Thus, Plant Biotechnology techniques are helpful in genetic modifications and inserting the desired trait into the crop plant with greater ease and thus contributes to crop improvement. It has become a prominent field of interest for future biotechnologist to work on plants and to overcome crop
plant’s related issues and to pace with the increasing food challenges in the future. 

References
Birhanu Babiye, Girma Haile, Mulugeta Adamu. (2020, August 27). Major Achievements of Plant
Biotechnology in Crop. Retrieved from Google Scholar:
https://www.researchgate.net/profile/Girma-
Alelign/publication/344121464_Major_Achievements_of_Plant_Biotechnology_in_Crop_Improv
ements/links/5f531d6a92851c250b9274dd/Major-Achievements-of-Plant-Biotechnology-in-
Crop-Improvements.pdf

Deepa Jaganathan, Karthikeyan Ramasamy, Gthandapani Sellamuthu, Shilpa Jayabalan, and Gayatri
Venkataraman. (2018, July 17). CRISPR for Crop Improvement: An Update Review. Retrieved
from Google Scholars: https://www.frontiersin.org/articles/10.3389/fpls.2018.00985/full
Novak, S. (2018). Plant Biotechnology Applications of Zinc Finger Technology. Retrieved from Google
Scholar: https://link.springer.com/protocol/10.1007/978-1-4939-8778-8_20

 

 By: Maha Aslam