| Fusarium head blight (FHB) is a devastating disease of wheat, and it widely occurs in the humid and semi-humid regions of the world. In China, FHB occurred seriously in the winter wheat area in middle and lower reaches of the Yangtze River and the spring wheat area in northeast China. In recent years the FHB occurred in Yellow River Basin and other wheat regions. The FHB reduces not only the yield and grain quality, but also seeding values. Due to the complexity of wheat genome and complicated nature of Fg-host interactions, the wheat genes regulating interactions with FHB responses remain largely unknown. Fhb1 is the most important QTL associating with FHB resistance in wheat,and it has been a hot spot of wheat genetic research community.In the current paper, we sequenced the RNA from NIL75 (FHB resistant) and NIL98 (FHB susceptible), two near isogenic lines (NILs) contrasting in Fhb1 alleles. The reads were de novo assembled without referring to the the reference sequences as well as blasted to the reference sequences. In the former case, there are 332 transcripts differentially expressed between NIL75 and S98, however, up to 2869 transcripts are differentially expressed in the latter case. Interestingly, several differentially expressed transcripts in common are involved in differentially expressed pathways including Phenylpropanoid biosynthesis, Flavonoid biosynthesis and ABC transporters, consistent with previous reports about scab resistance.In addition, we used the de novo assembled reads and original reads to blast the sequence of ctg0954b which harbored Fhb1 and found 10 differential expressed genes, In de novo assembled method, we identified one transcript that was expressed only in NIL98, but silenced in NIL75, and this transcript belongs to the unigene 29451 (temporarily designated as TaS410) that locates within Fhbl region between markers Xsts189 and Xsts142 on ctg0954b and encodes a protein with a domain of unknown function (DUF659) and an hAT (activator superfamily) dimerisation domain. Phylogenetic analysis suggests that TaS410 in wheat had the closest phylogenetic relationship with the ortholog in sorghum, and may be horizontally transferred from fungus during microbe-plant interactions. The expression of TaS410 in NIL98 was spatially and temporally heterogenous, and was upregulated after Fg challenge, probably atttributed to the presences of cis-elements responsive to pathogen challenge at the promoter region of TaS410. The expression of TaS410 is also detected in well-known FHB susceptible varieties including Wheaton, Jagger, Bobwhite and Clark, but is silenced in a panel of Fhb1-containing varieties including Ning7840, Wangshuibai, Huangfangzhu, Baisanyuehuang and Taiwan wheat. In NIL75, a nucleotide deletion on exon 4 of TaS410 probably resulted in a prematured termination of the transcription and gene silencing. These results imply that expression of TaS410 may be associated with increased FHB susceptibility and silencing this gene may lead to increased resistance in wheat. raS410-specific marker developed here could be used to assist in removal of the susceptible gene/allele to improve FHB resistance in wheat breeding. In addition, we detected TaS410-specific marker in Chinese mini core collection, the frequencies of TaS410 in landraces increases in the wheat regions from south to north as well as from east to west. High frequencies of TaS410 were also observed in commercial cultivars in most of the wheat regions. |
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