Roles Of AtWRKY28,AtWRKY63and AtWRKY75in Plant Responses To Oxalate And Oxalate-producing Fungi

Plant WRKY transcription factors are found to be involved in the regulation of plant physiological processes and respond to different biotic/abiotic stresses. In this study, we re-ported that Arabidopsis transcription factors WRKY28, WRKY63and WRKY75can response to oxalic acid stress, the three genes were significantly induced after spraying30mmol/L oxalic acid in Arabidopsis seedlings. Over-expression of these three genes in Arabidopsis enhanced resistance to oxalic acid significantly. Oxalic acid was generally considered as a key patho-genic factor in the necrotrophic pathogen Sclerotinia sclerotiorum. In this study, the experi-mental results of vivo/vitro inoculation of Sclerotinia sclerotiorum showed that the three WRKY genes enhanced resistance to Sclerotinia sclerotiorum notably; Moreover, Botrytis cinerea spray inoculation experiments confirmed that WRKY28over-expression mutants en-hanced resistance to Botrytis cinerea comparing with wild-type Co10. Trypan blue and DAB staining of24hours-post-inoculation Arabidopsis showed that WRKY63,WRKY75over-expression mutants had a significant oxidative burst comparing with wild-type Co10; The infection mycelium of Sclerotinia sclerotiorum growed crookedly and closely in WRKY63,WRKY75over-expression mutants,whereas, loosely in wild-type Co10. Moreover, PAL,POD and PPO enzyme activitives were determined in plants; Comparing with wild-type Co10, PAL showed no significant changes, POD increased and PPO decreased in WRKY63, WRKY75mutants.Interestingly, qRT-PCR revealed that WRKY28,WRKY75over-expression mutants both induced JA pathway marker gene PDF1.2, conversely the expression pattern was different in modulating SA pathway, PR1increased in WRKY28mutants, whereas decreased in WRKY75mutants. Analysis of the evolutionary tree of these three genes, we found transcription factors AtWRKY28, AtWRKY75showed a highly homologous to BnWRKY28-1, BnWRKY75-1in Brassica napus.The function analysis of these three genes can provide a theoretical basis for screening of Sclerotinia resistant mutants in Brassica napus.