Transcriptome-wide identification and expression analysis of ERF family genes in Actinidia valvata during waterlogging stress.

• A total of 131 ERF genes were identified and characterized in Actinidia valvata based on transcriptome analysis data. • AvERF73 and AvERF78 may play key roles for waterlogging responses in A. valvata. • This study furthers understanding the role of ERF and waterlogging-tolerance mechanism of A. valvata. Recently, there has been a tremendous increase in the cultivated area of kiwifruit in China. However, the low tolerance of most cultivars to waterlogging largely halted its expansion in waterlogged areas. Previously, some genotypes from Actinidia valvata , like KR5, were proved to be highly tolerant for waterlogging stress. ERF transcription factors, belong to the AP2/ERF superfamily, have played key roles in adaptation to waterlogging stress in numerous plant species. In this study, a total of 131 AvERF genes were identified based on the full-length transcriptome analysis data from KR5. By clustering with Arabidopsis thaliana ERFs, 131 AvERF proteins were sorted into eleven clades and renamed as AvERF1 to AvERF131. Within the same group, similar motifs for AvERFs were found in all members by MEME online tool. According to FPKM analysis, the expression of AvERF-VIIs in KR5 under waterlogging conditions was strongly promoted compared to other group members. Six genes from AvERF-VIIs (AvERF73 , AvERF75 , AvERF77 , AvERF78 , AvERF79 , and AvERF80) were chosen based on the higher fold changes in their expression against waterlogging. Moreover, their expression was evaluated in two tolerant genotypes: KR5 and KR1 from A. valvata , and two sensitive genotypes 'Xuxiang' and 'Hayward' from A. chinensis var. deliciosa during waterlogging stress by qRT-PCR. AvERF73 and AvERF78 were specifically induced in waterlogging-tolerant genotypes, but relatively low in the sensitive genotypes, indicating their positive roles in waterlogging tolerance. Both AvERF73 and AvERF78 had transcriptional activation activity. In the present study, we identified and characterized AvERFs into KR5 to reveal their importance in determining the waterlogging tolerance of kiwifruit. [ABSTRACT FROM AUTHOR]