Abstract
BackgroundFusarium fujikuroi is the causal agent of bakanae, the most significant seed-borne disease of rice. Molecular mechanisms regulating defence responses of rice towards this fungus are not yet fully known. To identify transcriptional mechanisms underpinning rice resistance, a RNA-seq comparative transcriptome profiling was conducted on infected seedlings of selected rice genotypes at one and three weeks post germination (wpg).ResultsTwelve rice genotypes were screened against bakanae disease leading to the identification of Selenio and Dorella as the most resistant and susceptible cultivars, respectively. Transcriptional changes were more appreciable at 3 wpg, suggesting that this infection stage is essential to study the resistance mechanisms: 3,119 DEGs were found in Selenio and 5,095 in Dorella. PR1, germin-like proteins, glycoside hydrolases, MAP kinases, and WRKY transcriptional factors were up-regulated in the resistant genotype upon infection with F. fujikuroi. Up-regulation of chitinases and down-regulation of MAP kinases and WRKY transcriptional factors were observed in the susceptible genotype. Gene ontology (GO) enrichment analyses detected in Selenio GO terms specific to response to F. fujikuroi: ‘response to chitin’, ‘jasmonic acid biosynthetic process’, and ‘plant-type hypersensitive response’, while Dorella activated different mechanisms, such as ‘response to salicylic acid stimulus’ and ‘gibberellin metabolic process’, which was in agreement with the production of gibberellin A3 in Dorella plants.ConclusionsRNA-seq profiling was performed for the first time to analyse response of rice to F. fujikuroi infection. Our findings allowed the identification of genes activated in one- and three- week-old rice seedlings of two genotypes infected with F. fujikuroi. Furthermore, we found the pathways involved in bakanae resistance, such as response to chitin, JA-dependent signalling and hypersensitive response. Collectively, this provides important information to elucidate the molecular and cellular processes occurring in rice during F. fujikuroi infection and to develop bakanae resistant rice germplasm.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2925-6) contains supplementary material, which is available to authorized users.
Highlights
Fusarium fujikuroi is the causal agent of bakanae, the most significant seed-borne disease of rice
The transcriptomic analysis allowed a remarkable insight into novel genes and pathways involved in defence of rice distinguishing two types of responses to bakanae disease
What was found strikingly different between resistant and susceptible response is the modulation of WRKY transcriptional factors and Mitogen-activated protein kinases (MAPKs) cascades, which are involved in induction of different plant signalling pathways [46, 49]
Summary
Fusarium fujikuroi is the causal agent of bakanae, the most significant seed-borne disease of rice. Bakanae disease or disease of foolish seedlings is one of the most important seed-borne diseases of rice, caused by the fungal pathogen Fusarium fujikuroi Nirenberg [teleomorph Gibberella fujikuroi (Sawada) Ito in Ito & K. As many Fusarium species, F. fujikuroi is a necrotrophic pathogen [5]. Though many rice cultivars (cvs.) have been screened for resistance to bakanae disease [8,9,10], to date no cultivar has shown a complete resistance, and despite the advancements in elucidating the F. fujikuroi genome [11, 12], there is still a limited knowledge on the mechanisms of rice resistance to bakanae, crucial for the development of appropriate control strategies
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