A CsEIL3-CsARN6.1 module promotes waterlogging-triggered adventitious root formation in cucumber by activating CsPrx5 expression.

Formation of adventitious roots (ARs) derived from hypocotyl is the most important morphological adaptation to waterlogging stress in cucumber. Our previous study showed that cucumber with gene CsARN6.1 encoding an AAA ATPase domain-containing protein was more tolerant to waterlogging due to high AR formation. However, the apparent function of CsARN6.1 was still unknown. Here, we showed that the CsARN6.1 signal was predominantly observed throughout the cambium of hypocotyls, where de novo AR primordia are formed upon waterlogging treatment. Silencing of CsARN6.1 expression by VIGS and CRISPR/Cas9 technologies adversely affects the AR formation under waterlogging conditions. Waterlogging treatment significantly induced ethylene production, thus upregulating CsEIL3 expression, which encodes a putative transcription factor involved in ethylene signaling. Furthermore, yeast one-hybrid, electrophoretic mobility assay, and transient expression analyses showed that CsEIL3 binds directly to the CsARN6.1 promoter to initiate its expression. CsARN6.1 was found to interact with CsPrx5, a waterlogging-responsive class III peroxidase that enhanced H 2 O 2 production and increased AR formation. These data provide insights into understanding the molecular mechanisms of AAA ATPase domain-containing protein and uncover a molecular mechanism that links the ethylene signaling to form the adventitious root triggered by waterlogging.