Slide 1 © CSIR The salicylic signalling pathway confers tolerance to a biotrophic rust pathogen in pearl millet Bridget Crampton Dave Berger

Slide 2 © CSIR Aims of the study  Elucidate defence response mechanisms in pearl millet  Evaluate pearl millet defence signalling pathways involved in leaf rust (Puccinia substriata) tolerance

Slide 3 © CSIR Pearl millet  Sixth most important cereal crop  Staple food in Africa and Asia  Cultivated for forage and grain  High temperature and drought tolerance  Abundant natural diversity  Resistance to diseases, insects and parasitic weeds  Defence response mechanisms poorly understood and not exploited

Slide 4 © CSIR Plant defence response mechanisms Compatible vs incompatible reaction PathogenHR SAR Salicylic acid = essential molecule in SAR induction Jasmonic acid and ethylene Salicylic acid

Slide 5 © CSIR Plant defence response mechanisms

Slide 6 © CSIR a a b waterwater + rustMeJa + rust SA + rust Defence signalling molecule treatment and subsequent rust infection  Arabidopsis – resistance to biotrophic pathogens = SA defence signalling

Slide 7 © CSIR Microarray preparation Chitin, flg, woundWater ID SSH/cDNA library Target amplification Array Spotter Probe preparation and hybridisation SA, MeJA,treatment 0, 12, 24 and 48 hpt RNA extraction Oh treatment12 h treatment Cy dye incorporation Hybridisation & scanning Data analysis Image analysis in Genepix Normalisation Average within slide replicates Average replicates between slides Up- and downregulated genes over time R//LimmaGUI/Excel

Slide 8 © CSIR A. Induced B. Repressed MeJASA MeJASA Regulatory relationship between SA and MeJA signalling pathways Relative to untreated control P<0.05

Slide 9 © CSIR SA responsive genes involved in resistance to rust

Slide 10 © CSIR qRT-PCR validation of microarray data

Slide 11 © CSIR Concluding remarks Pretreatment of pearl millet with salicylic acid conferred tolerance to subsequent rust infection. Gene expression analysis revealed substantial overlap in pearl millet’s gene expression responses to SA and MeJA treatments. Large scale gene expression profiling identified transcripts that were uniquely responsive to SA treatment.

Slide 12 © CSIR The way forward MicroArray Data Interface for Biological Annotation (MADIBA) Virus induced gene silencing (VIGS) Transgenic plant studies Promoter mining studies

Slide 13 © CSIR Publications Crampton BG, I Hein and DK Berger The salicylic acid signalling pathway confers tolerance to a biotrophic rust pathogen in pearl millet. In preparation. Berger DK, B Crampton, I Hein, and W Vos Screening cDNA libraries on glass slide microarrays, In: J. M. Walker (ed.), DNA Arrays. Humana Press, Totowa, New Jersey, USA. Van den Berg N, BG Crampton, I Hein, PRJ Birch and DK Berger High- throughput screening of suppression subtractive hybridization cDNA libraries using DNA microarray analysis. Biotechniques 37: O’Kennedy MM, B Crampton, and P Ozias-Akins P Pearl millet, In: “The Blackwell Handbook of Transgenic and Biotech Plants”. Wiley Blackwell, In Press.

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