Male Sterility is a condition in which the males produce unviable pollens. Barnase-barstar is a type of nuclear male genetic sterility

1. By Alicia Tiny
20LS401001
Msc Biotechnology
Barnase and
Barstar Sytem

2. Table of Contents
Hybrid seed
production
Advantages and
Disadvantages
Male sterility in
plants
Barnase – bartsar system
04
02
03
01

3. • Male sterility is characterized by the production of non- functional unviable pollen grains
while female gametes function normally.
• Koelreuter in 1763 first reported male sterility in flowering plants.
• Male sterility results from the action of nuclear genes or cytoplasmic genes or both.
Nuclear genetic male sterility is governed by single recessive gene ms.
Barnase-barstar system is a type nuclear genetic male sterility
Types of male sterility
1. Genetic male sterility
2. Cytoplasmic male sterility
3. Transgene male sterility
• Male sterility occurs in nature through spontaneous mutations as well as can be induced
artificially by chemical or physical mutagens. Ethidium bromide has been found effective
in inducing cytoplasmic male sterility in some plants.
Male sterility

4. • Barnase – barstar system is a type of nuclear genetic male
sterility.
• The first success in developing genetically engineered male
sterility in crop plants was achieved by Mariani in 1990 by
transforming tobacco and rapeseed plants with the barnase-
barstar system.
• Barnase and barstar are two small bacterial proteins, one a
ribonuclease and the other its specific inhibitor.
• Barnase, an extracellular enzyme secreted by Bacillus
amyloliquefaciens strain H (IAM1521), is one of a family of
small microbial ribonucleases.
• It was first reported and purified as an extracellular
ribonuclease of Bacillus subtilis H by Nishimura and Nomura.
• Its small size (110 amino acids, 12,382 Da) and does not
contains disulfide bonds.
Barnase-barstar system

5. • Barstar is an even smaller protein, with 89 amino acids (10,213 Da).
• It is produced intracellularly by B.amyloliquefaciens.
• It is a specific inhibitor of barnase ribonuclease. Barstar inhibits barnase
by forming with it a tight, one-to-one, noncovalent complex, prohibiting
access of substrates to the active site of the enzyme.
• The male fertility of barnase male sterile is restored by barstar

6. • A Line - It refers to genetic male sterile line (barnase) which is used as female
parent in hybrid seed production. It is a heterozygous line (barnase/-).
• B Line- It is a maintainer line. It is crossed with A line to maintain the male
sterility.
• R Line (Barstar): This line is used to store fertility in the F1 hybrid. Male
fertility is restored to a male-sterile line by introducing the fertility restorer gene
in the ms line
Components of Barnase-barstar system

7. 1. Chimeric RNase and barnase gene is driven under the control of tapetum specific
promoter TA 29
2. The tissue specific TA 29 gene is highly regulated and specifically expressed in tapetum
cells of anther. Expression of TA 29 and barnase fused gene consequently acts as
cytotoxic and selectively destroys the tapetal cell layer by complete elimination of RNA
molecule.
3. Barstar was fused to tapetum specific TA 29 gene upstream fragment that comprises all
regulatory segments targeted for tapetum specific expression.
4. Both barnase and barstar gene co-expressed specifically in the tapetal cells of anther led
to the formation of barstar-barnase stable complex. In the Fi progeny ratio of fertile to
sterile would be 2:1 ratio.
Mechanism

9. 1. Male sterile plants (barnase-bar/) are
crossed with male fertile plants( R
line).
2. Pollens will move from male fertile
plants to male sterile plants and
pollinate the male sterile plants.
3. The seeds from restorer lines must
be harvested to compare male sterile
plants.
4. After fertilization process two
genetically diverse seeds will be
formed.
Hybrid Seed Production

10. 1. It is not dependent on natural source of male sterility.
2. Transgenic male sterility can be used for the production of hybrid seed in both
seed propagated crops and vegetatively propagated species.
3. Transgenic male sterility is stable and provides a complete and usable male
sterility- restorer system.
4. Transgenic male sterility generally does not have undesirable agronomic
characters
5. Congenial conditions like temperature, photoperiods is not a requirement in
Barnase- barstar system.
6. This method produces pure hybrid seeds.
Advantages of Barnase- barstar system

11. 1. Fifty percentage of the population is lost, so more amount of female parent
seeds are needed for hybrid seed production.
2. It is an expensive method.
3. The method requires more area, labour, because the breeder has to maintain
many populations.
4. Since the seeds are transgene they face many ethical, social , environmental
and biological issues.
Disadvantages Barnase- barstar system

12. 1. In nature the availability of male sterility and fertility restoration sources are
limited. Therefore Barnase- barstar system provides us with a method to
develop male sterile plants. The method can be used for production of pure
hybrid seeds, that are stable and provide complete and usable male sterility
restorer system.
Conclusion

13. ● https://www.botanylibrary.com/plant-breeding-2/transgenic-male-
sterility/transgenic-male-sterility-meaning-features-plant-breeding-
botany/14026
● Robert W. Hartley, Barnase and barter, National Institute of health , 1997, pg-
51-57
● Subhash Chand, Om Prakash Patidar, Vijay Kamal Meena , Barnase-barstar
system : an inedible technique to produce hybrid seeds in self- pollinated
crops, International Journal of Farm Sciences 2018, 109-113
Bibliographical References