cytoplasmic genetic male sterility

role of male sterility i plant breeding
genetics and moleculr basis

1. WELCOME

2. MOLECULAR PERSPECTIVES OF CYTOPLASMIC -GENETIC MALE STERILITY CHAIRMAN Dr.K.R.SARAVANAN ASSISTANT PROFESSOR DEPT.OF GENETICS AND PLANT BREEDING   PRESENTED BY S.ABINAYA 18704001 MEMBERS: 1) Dr.S.RANJITH RAJARAM ASSISTANT PROFESSOR DEPT.OF GENETICS AND PLANT BREEDING 2) Dr.T.SIVAKUMAR ASSOCIATE PROFESSOR DEPT.OF.PLANT PATHOLOGY

3. CONTENT INTRODUCTION MALE STERILITY CGMS GENETICS AND MOLECULAR BASIS OF CMS/ Rf GENES FOR STERILITY AND FERTILITY RESTORATION FUTURE PERSPECTIVES

4. Plant breeding program aims to develop new improved cultivars and the development, involves selection of plants to be used as parents, crossing them to get F 1 . The breeder has to undergo procedure of emasculation and crossing technique. INTRODUCTION :

5. Plant breeding takes another shape when male sterility was identified. The sterility was long known in nature but the first report on male sterility was by Koelreuter in 1763. CONTD ..

6. Inabililty of plants to produce functional pollen is termed as male sterilty, while female gametes function normally. Main reason is mutation . MALE STERILITY

7. Why Male sterility more prevalent than female sterility? Less protected Easy to detect M.S Easy to assay M.S Propagation potential

8. CLASSIFICATION

9. It is governed by nuclear genes . In the system, there are A and B line. A line -genetic male sterile line (ms) B line -heterozygous male fertile line (Ms). A line is maintained by crossing it with B line, the cross produces male sterile and male fertile lines in 1:1 ratio. GENETIC MALE STERILITY

10. GMS

11. Cytoplasmic male sterility is governed by cytoplasmic or plasma genes. Progeny of male sterile plant is always male sterile, as its cytoplasm is derived entirely from female gamete.In the system, there are A and B line. Limitations: It cannot be used in sexually propagated crops, to produce hybrids in crops where improvement in seed / fruit is considered. CYTOPLASMIC MALE STERILITY

12. CMS

13. CYTOPLASMIC GENETIC MALE STERILITY 

14. It is governed by both nuclear and cytoplasmic genes .CGMS is also known as nucleoplasmatic male sterility . Here, nuclear genes for fertility restoration (Rf) are available. The fertility restorer gene R, is dominant and is found in certain strains of the species, or may be transferred from a related species CYTOPLASMIC GENETIC MALE STERILITY

15. There are commonly two types of cytoplasms , normal (F) and sterile (S). There are restorers of fertility ( Rf ) genes, which are distinct from genetic male sterility genes. The Rf genes do not have their own expression of any kind, unless the sterile cytoplasm is present. Rf genes are required to restore fertility in sterile cytoplasm which contains genes causing sterility. CONTD...

16. Maternally inherited trait Caused by the expression of aberrant chimeric genes locating on mitochondrial genomes. A number of CMS- determining genes have been identified. EXAMPLE - T- urf 13 gene in T-cytoplasm maize, orf79 and orf H79 in rice These genes are unusual open reading frame (ORFs) that have resulted from mitochondrial DNA rearrangements GENETICS AND MOLECULAR MECHANISM OF CMS/RF

17. Larger and more complex than those of other eukaryotic organisms. They contain a very active recombination system . Semi autonomous organelle PLANT MITOCHONDRIAL GENOME :

18. Mitochondrial genome contains 37 genes that encode 13 proteins,22 tRNAs,2rRNAs Donot follow universal coding pattern while translate protein. In mitochondria AUA code for methionine (not isoleucine ) UGA code for tryptophan(not a stop codon ) Transcrition - polycistronic CONTD..

19. PLANT MITOCHONDRIAL GENOME

20. MITOCHONDRIAL GENES Genes for respiratory chain functions: genes specify subunits Complex I , the NADH- dehydrogenase Complex II , the succinate dehydrogenase Complex III , the cytochrome -c reductase Complex IV , the cytochrome -c oxidase

21.   Pollen development requires higher levels of mitochondrial activity; even slight amount of mitochondrial dysfunction could result in pollen abortion. Mitochondria( chimeric gene) in the tapetum and the adjacent cell layer of sterile anthers start to degenerate soon after meiosis while in fertile anthers they remain intact.fig.1,fig.2 Affect the mitochondrial biogenesis in anther cell MECHANISM OF CYTOPLASMIC MALE STERILITY

22. Plant mitochondrial encodes a polypeptide which are component of ETC or ATPase -essential for respiration. Increase ROS (reactive oxygen species) Affected by presence of anther specific substance similar to Brassica maydis T. These substance interact with polypeptide like Turf 13 inhibit mitochondrial activity. CONTD..

23. Fig 1 pollen development in normal wild type

24. Fig 2. pollen degeneration after meiosis

25. CMS/ Rf in rice ( Oryza sativa ) : CMS/ Rf systems have been applied in over forty countries to breed hybrid rice ( Oryza sativa L.) with improved yields due to hybrid vigor. The production of hybrid rice mainly depends on three types of CMS systems, namely Wild-Abortive type CMS (CMS-WA), Hong- Lian type CMS (CMS-HL) Boro II type CMS (CMS-BT ).

26. A protein causing premature tapetal Programmed cell death: • The interaction of WA352 with OsCOX11,prevents the normal function of OsCOX11 in H 2 O 2 degradation. • COX11 protein is essential for the assembly of cytochrome oxidase . Restoration mechanism: • Restoration by either by Rf3 or Rf4 . • Rf4 causes 20-25% reduction in WA352 transcripts, but were not affected in the Rf3 carrying genes. • RF4 functions like RF1B that mediates the degradation of atp6-orf79mRNA. WA –CMS (wild abortive)

27. Mitochondrial disfunction orfH79 + P61 subunit of ETC complex III ETC activity reduced Increase in ROS and orfH79 accumulation Reduced ATP production Programmed Cell Death in Microspores . Fertility Restoration: • A Rf 5’s partner protein GRP162 ,can only bind to atp6-orfH79 through an RNA recognition motif. Interaction between these protein is called restoration of fertility complex (RFC) cleave atp6- orfH79. • Rf 6 gene can also restore the fertility of HL-CMS. HL-CMS (Hong lian )

28. Cytotoxicity and detoxification: • CMS is caused by a cytotoxic peptide, ORF79, encoded by mitochondrial dicistronic gene Batp6 orf79. • ORF79 is a transmembrane protein, accumulated in microspore . • Molecular mechanism is still unknown. Restoration: • By blocking ORF79 production through mRNA silencing • Endonucleolytic cleavage of the dicistronic B-atp6-orf79 mRNA by Rf1A and degradation by Rf1B leading to reduced orf79 expression BT-CMS

29. CMS genes are unknown. Restorer genes cloned: • Fertility of LD-CMS is restored by either Rf1 or Rf2. • Although it possesses chimeric atp6-orf79 dicistronic gene , L-atp6-orf79, CMS is not due to accumulation of ORF79. • In LD-CMS rf17 is the fertility restorer gene . • SNP in promoter region is speculated to restore compatibility between nucleus and mitochondria ,leading to male fertility . LD-CMS and CW-CMS

30. T- cytoplasm of maize cause male sterility.- sensitive to toxin Helminthosporium maydis race T. T- cms revert become resistant to toxic T-URF 13 and T-URF 25 – encode 13KDa and 25KDa polypeptide T-URF 13- resemble T- cms CYTOPLASMIC MALE STERILITY IN MAIZE:

31. Rf 1 and Rf 2 genes might restore fertility due to cause some changes in one of the transcript T-URF 13 Rf1 and Rf2 involves RNA synthesis and directly affect the synthesis of 13KDa protein

32. Fig.1. CHIMERIC CYTOPLASM MALE STERILITY (CMS)-ASSOCIATED REGIONS

33. Figure 1. Chimeric Genes Associated with CMS. Red indicates genes for subunits of ATP synthase . Shades of blue indicate unknown reading frames within CMS-associated regions. Shades of yellow indicate genes for subunits of cytochrome oxidase . Orange indicates ribosomal protein genes.Shades of brown indicate conserved unidentified reading frames found in multiple vascular plant mtDNAs . Green indicates chloroplast-derived sequences.

34. CYTOPLASMIC AND CYTOPLASMIC-GENETIC MALE STERILITY IN SOME IMPORTANT CROP PLANT

35. Need of commercialization of cytoplasm other than WA. The genetic and molecular basis is still not clearly understood for all the cytoplasm, this area need to be focused. Their should be expansion of germplasm use to widen the genetic base for hybrid rice production. With the increasing population it’s a challenge to secure high heterosis levels in hybrid rice. FUTURE PERSPECTIVES