Transcriptome Analysis Of Haidao 86 Infected By Magnaporthe Oryzae At Different Time Points

Rice blast is the most destructive fungal disease of rice worldwide and occurs in all rice-growing stages.Haidao 86 is a new rice cultivar which can grow in coastal tidal-flat area and saline field.It was reported that Haidao 86 has a high salt tolerance and rice blast resistance.Fresh water was used in the cultivation of Haidao 86.Haidao 86 exhibited mid-resistance to rice blast 00-193,which was inconsistent with the declared high resistance in the report.The reason for the difference in resistance may be the lack of salt in the plant environment.In this study,comparative transcriptome profiling of Haidao 86 with Magnaporthe oryzae infection at different time points(0,12,24 and 48 hpi)were investigated using RNA sequencing.The results generated at least 7524,643 unique reads mapped to the rice genome.In total,2267 differentially expressed genes(DEGs)were identified with 4,382,1313 and 1190 DEGs at 0,12,24 and 48 hpi respectively.Hierarchical cluster analysis showed that samples collected at 12 hpi were more similar to the controls than 24 hpi,which means the transcription of Haidao 86 changed after the infection of 24 hours.The result of GO analysis showed that most of the DEGs were significantly enriched in GO items such as photosynthesis,metabolic process and ion transport.KEGG analysis showed that most of the DEGs existed in pathways such as photosynthesis-antenna proteins,secondary substances metabolism and plant hormone signal transduction.DEGs related to terpenoid biosynthetic process(including monoterpenes and diterpenes),plant hormones(JA,SA,and ET)and detoxification enzymes(GST)may enhance the rice blast resistance of Haidao 86.We identified 1007 transcription factor genes including bHLH,NAC,MYB and WRKY families that show differential expression in this study.In WRKY family,WRKY13,WRKY71 and WRKY45-2 may play an important role in rice blast resistance of Haidao 86.The expression levels of WRKY13 was up-regulated in the early stage of M.oryzae infection,peaked at 24 hpi,and then declined.The expression level of WRKY71 was up-regulated at 12 hpi.The expression level of WRKY45-2 was down-regulated after M.oryzae infection.We also identified two resistance genes which may be involved in the defense response of Haidao 86.BGIOSGA015709 may encode resistance protein RGA4 which was up-regulated in the early stage of M.oryzae infection and was down-regulated in the later stage.BGIOSGA019677 may encode resistance protein RGA1 which was down-regulated after infection.The overexpression of WRKY13,WRKY71 and RGA4,the low expression of WRKY45-2 and RGA1 contributed to the improvement of rice defense response.