Waterlogging-induced increase in fermentation and related gene expression in the root of cucumber (Cucumis sativus L.)

• Root activities and cell death appeared different injury degree under different waterlogging intensity.
• Changes in fermentative genes expression, PDC, ADH and LDH activities, concentrations of acetaldehyde, alcohol and lactate were related to waterlogging stress.
• The operation of alcohol fermentation under waterlogging stress might be an important reason for root death.

Waterlogging usually leads plant cells to shift their metabolism towards anaerobic fermentation pathways due to the hypoxia stress. The roles of two different levels of waterlogging treatments (water level was kept on the base of hypocotyls and on the base of the first true leaf) in induction of fermentation in waterlogged roots of cucumber line ‘Zaoer-N’ (waterlogging tolerant line) were examined. Root activities, numbers of dead cells, transcripts of genes encoding pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH), and activities of the PDC, ADH, and LDH enzymes, concentrations of acetaldehyde, alcohol and lactate were quantified during 48 h of waterlogging, and 48 h of subsequent recovery. The results showed that PDC, ADH, and LDH transcripts, activities of PDC, ADH and LDH, and concentrations of acetaldehyde, alcohol and lactate were upregulated or increased during waterlogging, and decreased with recovery time prolonged. The results revealed that waterlogging up to the base of first true leaf responded more severe than waterlogging up to the base of hypocotyls in root activity and numbers of dead cells, which were mainly caused by alcohol fermentation.