Genome-wide Characterization,Expression Patterns And Disease Resistant Function Of The PLATZ Gene Family In Watermelon

Plants are constantly suffered from a variety of biotic and abiotic stresses during their lifespan.To adapt to these adversities,plants have evolved complicated molecular mechanisms that recognize environmental stress signals and balance their growth/development and defense responses,including the transcriptional regulation mechanism of gene expression in response to biotic and abiotic stresses.PLATZ(plant AT-rich sequence and zinc-binding protein)is a novel class of plant-specific DNA-binding proteins that show non-specific binding to A/T-rich sequences and inhibit transcription of downstream target genes.PLATZs in rice and Arabidopsis have been shown to be involved in multiple biological processes such as cell proliferation,leaf development and senescence,drought stress response.The present study aimed to identify the PLATZ family genes in Cucurbita crops,analyze ClPLATZs expression patterns and explore ClPLATZ potential functions in biotic and abiotic stress responses.(1)Using bioinformatics approaches,10 watermelon PLATZ family members,10 melon PLATZ family members,12 cucumber PLATZ family members,20 Cucurbita moschata PLATZ family members and 20 zucchini PLATZ family members were identified from the Cucurbita genome database.Amino acid sequence alignments and conserved domain analysis indicated that all the PLATZ proteins of the Cucurbita crops contained conserved PLATZ domain.All of the watermelon PLATZ genes were confirmed by cloning and sequencing.(2)Most of the PLATZ genes in watermelon showed the highest expression level in roots and the lowest in leaves;ClPLATZ5 was significantly up-regulated,while ClPLATZ10 was significantly down-regulated after SA treatment.ClPLATZ1 and ClPLATZ5 were significantly down-regulated,ClPLATZ7 was significantly up-regulated by Me JA.After inoculation with Fusarium oxysporum f.sp.niveum,a large number of PLATZ family genes were significantly up-regulated in root tissues.After inoculation with Didymella bryoniae,most of the PLATZ family genes were significantly down-regulated in leaf tissues.(3)ClPLATZ6,ClPLATZ7,ClPLATZ8 and ClPLATZ9 localized in the nucleus of the cells,while ClPLATZ1,ClPLATZ2,ClPLATZ3,ClPLATZ4,ClPLATZ5 and ClPLATZ10 distributed throughout the cells.ClPLATZ family proteins partially interacted with DP,26 S and RPC53,which were related to the cell division and proliferation.(4)The functions of ClPLATZ genes in biotic stress and abiotic stress responses were analyzed by ectopic expression in Arabidopsis.Compared with wild-type Col-0plants,the ClPLATZ9-OE plants displayed smaller disease lesions,while ClPLATZ6-OE and ClPLATZ10-OE plants showed larger disease lesions after inoculation with Botrytis cinerea,indicating that ClPLATZ9 played a positive role in resistance to B.cinerea,while ClPLATZ6 and ClPLATZ10 were negative regulators of Botrytis resistance.After inoculation with Pseudomonas syrinage pv.tomato(Pst)DC3000,disease severity and the growth of PstDC3000 in ClPLATZ2-OE or ClPLATZ6-OE plants were significantly reduced,while the disease severity and the growth of PstDC3000 in ClPLATZ9-OE plants were significantly increased,as compared with those in wild type plants,implying that ClPLATZ2 and ClPLATZ6 were positive regulators of defense responses against PstDC3000,while ClPLATZ9 was a negative regulator of PstDC3000 resistance.Furthermore,tolerance of ClPLATZ9-OE plants to Na Cland mannitol was significantly increased as compared with that of the wild type at seed germination stage.