ANALYSIS OF ACUTE COLD STRESS-INDUCED DISEASE RESISTANCE (SIDR) AGAINST POWDERY MILDEW IN ARABIDOPSIS THALIANA
Acute cold events (2 – 8 Celsius degrees) often hinder the development of not only field crops but also phytopathogens by establishing a cold stress-induced disease resistance (cold SIDR). Although the cold SIDR phenomenon had been discovered in a series of important economical crops with different kingdoms of pathogens, the genetic mechanism and regulation network remained elusive. Therefore, in this thesis, a model plant species Arabidopsis thaliana was utilized to analyze the cold SIDR phenomenon with fungal pathosystem. A time-course infection experiment was carried to acquire the 3’ RNA sequencing data, and compare the differences across various post-cold treatment time period. A plant immunity defective SNARE mutant, pen1-1, was also included to compare with the wild type plant groups. Moreover, a group of plant immunity related mutants (pad4, snc1, aca8/10, aca4/11) were tested in the fungal infection assays to reveal the potential regulatory network and key genes initiating the cold SIDR. The RNA sequencing of salicylic acid related plant immunity genes and biosynthesis genes were filtered and separately analyzed. The infection assay on wild type and pen1-1 plants exhibited that 12 and 24 hours after cold events led to higher cold SIDR. The cold SIDR were not established in the pen1-1 groups, and all other investigated plant immunity related mutants. The RNA sequencing results indicated several crucial biological processes, such as photosynthesis, plant hormone regulation and carbon metabolism, were closely associated with the cold SIDR. Several vital salicylic acid responsive or biosynthetic genes, such as EDS5, SADR1, and NPR gene family, were found differentially expressed at basal level (immediately after cold), 12 or 24 hours post the cold events.