Abstract
BackgroundThe fungal pathogen Setosphaeria turcica causes turcicum or northern leaf blight disease on maize, sorghum and related grasses. A prevalent foliar disease found worldwide where the two host crops, maize and sorghum are grown. The aim of the present study was to find genes controlling the host defense response to this devastating plant pathogen. A cDNA-AFLP approach was taken to identify candidate sequences, which functions were further validated via virus induced gene silencing (VIGS), and real-time PCR analysis. Phylogenetic analysis was performed to address evolutionary events.ResultscDNA-AFLP analysis was run on susceptible and resistant sorghum and maize genotypes to identify resistance-related sequences. One CC-NB-LRR encoding gene GRMZM2G005347 was found among the up-regulated maize transcripts after fungal challenge. The new plant resistance gene was designated as St referring to S. turcica. Genome sequence comparison revealed that the CC-NB-LRR encoding St genes are located on chromosome 2 in maize, and on chromosome 5 in sorghum. The six St sorghum genes reside in three pairs in one locus. When the sorghum St genes were silenced via VIGS, the resistance was clearly compromised, an observation that was supported by real-time PCR. Database searches and phylogenetic analysis suggest that the St genes have a common ancestor present before the grass subfamily split 50-70 million years ago. Today, 6 genes are present in sorghum, 9 in rice and foxtail millet, respectively, 3 in maize and 4 in Brachypodium distachyon. The St gene homologs have all highly conserved sequences, and commonly reside as gene pairs in the grass genomes.ConclusionsResistance genes to S. turcica, with a CC-NB-LRR protein domain architecture, have been found in maize and sorghum. VIGS analysis revealed their importance in the surveillance to S. turcica in sorghum. The St genes are highly conserved in sorghum, rice, foxtail millet, maize and Brachypodium, suggesting an essential evolutionary function.
Highlights
The fungal pathogen Setosphaeria turcica causes turcicum or northern leaf blight disease on maize, sorghum and related grasses
We found one R-gene cluster, containing six CC-nucleotide-binding site (NB)-leucine-rich repeats (LRR) encoding genes residing as three pairs in the sorghum genome, of importance for defense to S. turcica
Apart from S. turcica responses, GA06/18 was found to be susceptible to Cercospora sorghi, and Colletotrichum sublineolum, whereas Sila was susceptible to C. sorghi and resistant to C. sublineolum
Summary
The fungal pathogen Setosphaeria turcica causes turcicum or northern leaf blight disease on maize, sorghum and related grasses. The aim of the present study was to find genes controlling the host defense response to this devastating plant pathogen. Recognition of pathogens in a species-specific way results in the generation of a very robust mode of surveillance system in plants. This form of protection termed resistance (R) protein-mediated or effector-triggered immunity is induced when a plant encoded R protein “perceives” the presence of a pathogen-derived effector molecule, represented by specific avirulence (Avr) gene products [1]. The LRR domain may determine the final outcome of this recognition, leading to downstream signaling and initiation of defense responses [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
