Genetic En g ineering

1. Genetic Engineering

2. PLANT DISEASERESISTANCE AND GENETICENGINEERING

3. What is a plant disease? • A plant disease is any abnormal condition that alters the abnormal growth or function of a plant. Disease may also reduce yield and quality of harvestedproduct. • Plant diseases are classified in 2categories: • Abiotic • Biotic

4. Abiotic Diseases • Are caused by (non-living)environmental conditions such as frost, hail, and chemicalburn. • Damage caused by chronic exposureto air pollutants such as nitrogen dioxide, sulfur dioxideetc.

5. BioticDiseases • Are caused by living organisms suchas fungi, bacteria, viruses, nematodes,etc. • Pathogens may infect all types ofplant tissues to include leaves, shoots,roots, fruit, s eedsetc.

6. The DiseaseTriangle • For a biotic disease to occur there mustbe a susceptible host plant, the pathogen, optimum environmentalconditions.

7. The DiseaseCycle • The development of visual disease symptoms on a plant requires thatthe pathogenmust • come into contact with asusceptible host • gain entrance or penetrate the host through either a wound, a naturalopening or via direct penetration of thehost • establish itself within thehost • grow and reproduce within or onthe host

8. BioticComponents • Fungi:- • They damage plants by killing cells orcausing plantstress. • Sources are infected seed, soil, cropdebris, nearby crops and weed, which spread by wind and water splash, and through the movement of contaminated soiletc. • They enter plants through natural openings such as stomata and through wounds caused by pruning, harvesting, hail, insects, other diseases, and mechanicaldamage.

9. Common fungaldiseases • White blister/Whiterust • Clubroot • Botrytisrots • Anthracnose • Tuberdiseases

10. ViralInfections • Viruses cause many plantdiseases. The spread of most viruses is very difficult tocontrol. • Viruses are often transmittedfrom plant to plant byinsects. • Normally, when a RNA virus attacksa cell, it will produce enormous number of copies of itself. The copies, in turn, produce viral protein, which can help to disable the cells defenses to the virus.

11. One way of preventing viral infections is by giving a plant a viral gene encoding the virus' 'coat protein'. The plant then produces this viral proteinbefore • the virus infects the plant. Ifthe • virus arrives, it is not able toreproduce. • This is called co-suppression. When a foreign viral DNA enters the plant cell, viral coat protein is produced, and it eventually shuts down the viral protein's expression. When the virus tries toinfect the plant, the production ofits • essential coat protein is alreadyblocked.

12. VCPs encapsulate the viral nucleic acid and are thought to be importantin nearly every stage of viral infection including replication, movement throughout an infected plant, and transport from plant toplant

13. Alternatively, apical or axillary meristems are generally free fromviral particles, which has helped the scientists to produce virus free plants, by culturing small meristems collected from virus infectedplants.

14. Gene Transfer inplants • Vector used: Ti plasmid of AgrobacteriumTumefaciens. • Ti Plasmid- Tumor Inducing Plasmid with TransferDNA. • Strategy: • Collect leafdiscs • Infect the tissue withAgrobacterium carrying recombinant Tiplasmid.

15. The infected tissue is then raised inShoot regeneration medium for 2-3 days, sothat transfer of T-DNA along with gene of interest takesplace. • Then the transformed tissues are transferred onto selection cum plant regeneration medium supplemented with usually lethal concentration of anantibiotic. • This medium also contains abacteriostatic agent, which suppresses the Agrobacterium present with the transformedtissues.

16. After 3-5 weeks, the regeneratedshoots are transferred to root inducingmedium. • After another 3-4 weeks, complete plants are obtained, which are transferred tosoil, following the hardening of regenerated plants.

17. Late Blight inPotato • produce millions of spores frominfected plants under the wet weather conditions that favor thedisease. • Spores produced on infected potatoescan travel through the air, land on infected plants, and if the weather is sufficiently wet, cause newinfections.

18. Late blight is caused by theoomycete • Phytophthorainfestans. • Several R genes originating from introgressions of S. demissum have been mapped to potato chromosomes using DNA markers. • the molecular cloning of R1 gene for resistance to late blight that is located in the resistance hot spot on potato chromosomeV. • R1 among plant resistance genes containing a conserved nucleotide binding domain (NBS), a leucine-rich repeat domain (LRR) and a leucine zippermotif.

19. 300 Restriction fragmentlength polymorphism(RFLPmarkers) • Race specific and hyper sensitive to p.infectants • Those groups were R1, R3, R4, R10and groups with a larger amount of accumulated R alleles and 90 different clones belonging to the species S. demissum, S. tuberosum ssp.andigena, • S. phureja, S. bulbocastanum andS. stoloni

21. Remaining clones in the physical mapare BACs with lengths between 70 and 100 kb. • Grey bars: BACs from thechromosome carryingr1. • Solid black bars: BACs fromthe chromosome carryingR1. • Mapped BAC ends are indicated bythe number of recombinants separatingthe BAC end fromR1.