Antisense RNA is the complementary RNA to the protein-coding messenger mRNA. The antisense mRNA binds to sense mRNA and the translation was restricted, that is called translation arrest. The nature antisense RNA technology present in hok &sok in E.coli R1 plasmid. The artificial or purpose antisense RNA technology best example is flavr savr tomato.

2. INTRODUCTION
 Antisense RNA is a single standard RNA that is complementary to a protein coding
messenger RNA (mRNA) with which it hybridizes , and thereby blocks its translation
into protein.
 Example : hok /sok system of the E.coli R1 plasmid.
This translational arrest causes reduced amount of protein expression.
Well-known examples of GM plants produced by this technology –
 the Flavr savr tomato
 Two cultivars of ring spot – resistant papaya.
HISTORY:
 Antisense effect first demonstrated by Zemen nick & Stephenson in 1970 on
“Rous sarcoma virus” .
First time antisense oligonucleotides are synthesized by Eckstein and colleagues.

3. GENERAL OUTLINE

4. NATURE’S ANTISENSE SYSTEM
 There is HOK (host killing)/ SOK (suppress killing) system in R1 plasmid in E.coli.
 when E.coli cell undergoes division ,daughter cell inherit hok gene & sok gene from
parent . But due to short life of cell , the sok gene is get degraded. So in normal cell ,
hok gene get over expressed & cell get die.
 But when R1 plasmid is get inherited ,it having the sok gene & sok promotor.
 Then it transcripts sok gene & it is get over expressed against hok gene.

6. PURPOSE ANTISENSE SYSTEM
 The Flavr savr tomato is the best example of purpose antisense RNA technology.
 In normal tomato have a PTOM6 gene for tomato ripening process.
 This PTOM6 gene produce polygalacturonase (PG) enzyme . The PG is the major cell
wall degrading enzyme of tomato fruit.
 It is developmentally regulated and is synthesized de novo is ripening fruit.
 The FLAVR SAVR tomato was developed through the use of antisense RNA to
regulate the expression of the enzyme polygacturonase (PG) in ripening tomato fruit.
 we are purposely introduced a gene in plant which synthesize a complementary
mRNA to polygalacturonase (PG) gene and inhibiting the synthesis of
polygalacturonase enzyme.
 ripe tomatoes produced in this way will not rot for 3 weeks.

8. MECHANISM
 In this technique , short segments of single standard RNA are introduced .
 These oligonucleotides are complementary to the mRNA which physically bind to the
mRNA.
 So, they block the expression of particular gene .
 In the of virues , antisense oligonucleotides inhibit viral replication with blocking
expression of integrated proviral genes.
 Usually consists of 15-20 nucleotides .
 Translation of mRNA may be blocked by two possible mechanisms , these are :
1. By base specific hybridization : which prevents access by translation
machinery i.e. hybridization arrest .
2. By forming RNA/DNA duplex : which is recognized by nuclease Rnase
H , specific for digesting RNA in an RNA/DNA duplex.
 RNase H is a non specific endonuclease , catalyzes the cleavage of RNA via hydrolytic
mechanism.

10. APPLICATIONS
 Flavr savr tomato :
Antisense RNA used against an enzyme polygacturonase , an softening enzyme
which is responsible for ripening .
 Transgenic ACMV :
Resistant cassava plants – used against African cassava mosaic virus (ACMV)
which causes cassava mosaic disease causing major economic loss in Africa.
 Formivirsen – is the first antiviral drug developed against CMV.