Identification and functional analyses of the transcription factors AcWRKY117 and AcWRKY29 involved in waterlogging response in kiwifruit plant

Waterlogging is becoming an increasingly significant problem for crop production and food security. As one of the largest transcription factor (TFs) families in plant crops, WRKYs are reported to be involved in various abiotic stress responses, including waterlogging resistance. However, little is known about the molecular regulation of WRKYs responding to waterlogging stress in kiwifruit plant (Actinidia chinensis). Based on the transcriptome and genome database, a total of 112 AcWRKYs, which were divided into seven subgroups, had been identified in A. chinensis cv. Donghong. Transcript levels of 7 out of these 112 AcWRKYs showed closely correlation with increasing of acetaldehyde and ethanol contents resulted from the high expression of AcPDCs and AcADHs during waterlogging response of the roots. AcWRKY117 and AcWRKY29, which were clustered into group I and II-e respectively, had been verified to trans-activate the expression of AcPDC2 based on the results of dual lucif-erase assays. Both AcWRKY117 and AcWRKY29 could bind to the w-box (5 '-TGACC (A/T)-3 ') motif located in target promoter of AcPDC2. Furthermore, contents of acetaldehyde and ethanol in both 35S::AcWRKY117 and 35S::AcWRKY29 overexpression kiwifruit calli had been significantly increased. These were consisted with the significant higher transcript levels of AcPDCs and AcADHs, as well as AcERF74 and AcERF75 which trans-activate the activity of AcADH1 promoter, in the transgenic kiwifruit calli. Moreover, the expression pattern of AcWRKY117 had been dramatically induced in 35S::AcWRKY29 transgenic lines, and vice verse. Taken together, our results provide molecular evidence for WRKYs regulation on waterlogging response in kiwifruit.