1. RESISTANCE GENE IDENTIFICATION IN BARLEY AGAINST FUSARIUM HEAD
BLIGHT BASED ON METABOLO-TRANSCRIPTOMICS APPROACH
Shailesh Karre
PhD abstract:
Barley is one of the important cereal food crops in the world, mainly due to its wonderful
versatility. Fusarium head blight (FHB) caused by Fusarium graminearum is considered as one of
the biggest problems in barley production, because it leads to serious yield loss and also mycotoxin
contamination of grains. The management of FHB is a great challenge in barley and wheat
production worldwide. Though barley genome sequences and advanced omics technologies are
available, till date none of the resistance mechanisms has been successfully deciphered. Hence,
this study was aimed at identifying candidate gene(s) and elucidating resistance mechanisms
induced by barley resistant genotype ‘CI9831’ based on integrated OMICS approach. Preliminary
results from metabolo-transcriptomics platform identified accumulation of specific set of induced
secondary metabolites and upregulation of biosynthetic genes in the phenylpropanoid,
hydroxycinnamic acid (HCAA) and jasmonic acid pathways. In addition, several regulatory genes
such chitin elicitor receptor kinase (HvCERK1), MAPK kinases like HvMPK3 and HvMKS1, and
transcription factors such as HvERF1/5, HvNAC42, HvWRKY23 and HvWRKY70 were also
upregulated following pathogen inoculation. Sequencing studies and expression analysis of four
barley genotypes identified HvCERK1 and HvWRKY23 as two candidate genes, which were found
functional in resistant genotype ‘CI9831’. Functional validation of HvCERK1 and HvWRKY23
based on virus induced gene silencing (VIGS), not only increased fungal biomass in resistant
genotype ‘CI9831’, but also identified respective downstream targets at gene and metabolite
levels. In silico and in vivo protein-DNA interaction studies revealed the transcriptional regulation
of downstream biosynthetic genes such as HvPAL2, HvCHS1, HvHCT, HvLAC15 and HvUDPGT
which are the biosynthetic genes of resistant related (RR) metabolites belonging to flavonoid and
HCAA pathways. Among several FHB related studies in barley, this is the first study to report the
role of receptor gene, HvCERK1 and transcription factor, HvWRKY23 in regulating biosynthesis
of RR metabolites that directly suppressed the pathogen progress in plant. Thus identified
candidate genes can further be transferred to susceptible genotypes, either through molecular
breeding or genome editing based on CRISPR-Cas9 system.