Day 2 :
Professor The Samuel Roberts Noble Foundation, USA
Keynote: Insertion Mutagenesis of Medicago truncatula and its Utilization to Identify Novel Sources of Resistance against Asian Soybean Rust
Time : 9:30-10:15
KIRAN MYSORE is a Professor at the Noble Research Institute. He joined the Noble in 2002. He also holds Adjunct Professorship at the Department of Entomology and Plant Pathology, Oklahoma State University. He received his Bachelor’s degree in Agriculture at the University of Agricultural Sciences, Bangalore (India), Master’s degree in Horticulture at Clemson University and Ph. D. in Genetics at Purdue University in 1999. He did his postdoctoral training at the Boyce Thompson Institute for Plant Research, Cornell University. His main research interests center on molecular plant-microbe interactions. Research approaches in his group include genetics and genomics to better understand how plants defend against pathogens. In addition, he has developed genetic resources (Tnt1 insertion lines) in Medicago truncatula that is now widely used by the legume community. He has published over 150 papers and book chapters in international journals
Retrotransposons, retrovirus-like elements which encode proteins required for their own replication and transposition, can be used for insertional mutagenesis. Retrotransposons can be activated by tissue culture and preferentially insert in gene-rich regions of the genome. The absence of excision during transposition makes retrotransposons ideal for saturation mutagenesis with stable tags. Tobacco retrotransposon, Tnt1, has been used to mutagenize and tag the whole genome of a model legume, Medicago truncatula. Tnt1 is very active and transpose into, on average, 25 different locations during M. truncatula tissue culture. Mutations induced by Tnt1 insertion are stable during seed to seed generation. We have generated over 20,000 independent Tnt1-containing lines encompassing approximately 500,000 insertion events. Over 300,000 Tnt1 flanking sequence tags (FSTs) have been recovered and a database has been established. We have pooled genomic DNA from all the lines for customized reverse-genetic screening, and the frequency of insert identification in this pool for average-sized-gene is approximately 85% percent. The range and diversity of mutant phenotypes obtained to date suggest that M. truncatula offers a great opportunity to dissect symbiotic and developmental pathways for comprehensive understanding of legume biology. A forward genetics approach using Tnt1 tagged M. truncatula lines has been established (Fig. 1) to identify genes that confer nonhost resistance to Asian Soybean Rust pathogen, Phakopsora pachyrhizi. Several M. truncatula Tnt1 mutants with altered response to P. pachyrhizi have been identified and being characterized. irg1 (inhibitor of rust germ-tube differentation1) mutant inhibited pre-infection structure differentiation of P. pachyrhizi and several other biotrophic pathogens. IRG1 encodes a Cys(2)His(2) zinc finger transcription factor, PALM1 that also controls dissected leaf morphology in M. truncatula. Characterization of other mutants will also be presented.
The University of Western Australia, Australia
Keynote: Advanced reference genome of Trifolium subterraneum L. reveals loci governing important agronomictraits for biotechnological improvement of forage legumes
Time : 10:15-11:00
for Plant Genetics and Breeding (PGB) at the University of Western Australia. Dr Kaur has received the Science and Innovation Award for young people in Agriculture, Fisheries and Forestry in 2013 and produced the world first genome scaffold for subterranean clover using the de-novo sequencing pipelines anchored to a high resolution genetic map and BioNano optical maps for trait mapping. She has been working with a team of researchers across various disciplines to develop methodologies to enable breeders to identify environmentally friendly pasture legume to tackle future challenges for Australian livestock industries
Subterranean clover is an important annual forage legume, whose diploidy and inbreeding nature make it an ideal model for genomic analysis in Trifolium. We reported a draft genome assembly of the subterranean clover TSUd_r1.1. Here we evaluate genome mapping on nanochannel arrays and generation of a transcriptome atlas across tissues to advance the assembly and gene annotation. Using a BioNano-based assembly spanning 512 Mb (93% genome coverage), we validated the draft assembly, anchored unplaced contigs and resolved misassemblies. Multiple contigs (264) from the draft assembly coalesced into 97 super-scaffolds (43% of genome). Sequences longer than >1 Mb increased from 40 to 189 Mb giving 1.4-fold increase in N50 with total genome in pseudomolecules improved from 73 to 80%. The advanced assembly was re-annotated using transcriptome atlas data to contain 31,272 protein-coding genes capturing >96% of the gene content. Functional characterisation and GO enrichment confirmed gene expression for response to water deprivation, flavonoid biosynthesis, and embryo development ending in seed dormancy, reflecting adaptation to the harsh Mediterranean environment. Comparative analyses across Papilionoideae identified 24,893 Trifolium-specific and 6,325 subterranean-clover-specific genes that could be mined further for traits such as geocarpy and grazing tolerance. Eight key traits, including persistence, improved livestock health by isoflavonoid production in addition to important agro-morphological traits, were fine-mapped on the high density SNP linkage map anchored to the assembly. This new genomic information is crucial to identify loci governing traits allowing marker-assisted breeding, comparative mapping and identification of tissue-specific gene promoters for biotechnological improvement of forage legumes.