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microRNA

A team from the National Centre for Biological Sciences (NCBS), Bengaluru, has found that the rich colour in fruits and leaves of plants are indirectly controlled by specific micro RNAs, miR828 and miR858.

What is microRNA?

  • A microRNA, also known as miRNA is a small non-coding Ribonucleic acid (RNA) molecule containing about 22 nucleotides.
  • It is found in plants, animals and some viruses that functions in RNA silencing and post-transcriptional regulation of gene expression.
  • miRNAs function via base-pairing with complementary sequences within mRNA molecules.
  • As a result, these mRNA molecules are silenced, by one or more of the following processes

Cleavage of the mRNA strand into two pieces.

  • Destabilization of the mRNA through shortening of its poly(A) tail.
  • Less efficient translation of the mRNA into proteins by ribosomes.

How micro RNAs regulate the colour of fruits, leaves?

  • Grape plants bear fruits having colours that can be deep purple or green.
  • This colour is due to compounds called anthocyanins and flavonols, both of which are present in grape fruits.
  • When the grape plant has a high amount of anthocyanin as compared to flavonol, the fruits are deep purple.
  • When the reverse is true, the grapes are not brightly coloured.
  • The relative abundance of anthocyanin and flavonol is controlled by genes known as the MYB transcription factors.
  • They are also referred to as activators.
  • When present in large amounts, they result in dark purple grape, as in the Bangalore Blue variety, and absence correlates with lack of bright colour but high incidence of flavonols as in the Dilkhush grape variety.
  • Micro RNAs are regulators of gene expression, acting like switches.
  • They decide which protein should be made and how much in a given cell or tissue or an organism.
  • They are tiny, having some 20 to 22 digits of RNA.
  • The miRNA inhibit target RNAs by cutting them into two bits in plants.
  • The miRNAs partner with a protein called Argonaute to do this regulation.

Bio fortification

  • Bio fortification is the process by which the nutritional quality of food crops is improved through agronomic practices, conventional plant breeding, or modern biotechnology.
  • Plants having anthocyanin and flavonol can be generated by controlling the microRNAs affecting them,which can be used in biofortification.
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October 2022
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