Abstract
Tomato (Solanum lycopersicum L.) is a vegetable frequently exposed to hypoxia stress induced either by being submerged, flooded or provided with limited oxygen in hydroponic cultivation systems. The purpose of the study was to establish the metabolic mechanisms responsible for overcoming hypoxia in two tomato accessions with different tolerance to this stress, selected based on morphological and physiological parameters. For this purpose, 3-week-old plants (plants at the juvenile stage) of waterlogging-tolerant (WL-T), i.e., POL 7/15, and waterlogging-sensitive (WL-S), i.e., PZ 215, accessions were exposed to hypoxia stress (waterlogging) for 7 days, then the plants were allowed to recover for 14 days, after which another 7 days of hypoxia treatment was applied. Root samples were collected at the end of each time-point and 2D-DIGE with MALDI TOF/TOF, and expression analyses of gene and protein-encoded alcohol dehydrogenase (ADH2) and immunolabelling of ADH were conducted. After collating the obtained results, the different responses to hypoxia stress in the selected tomato accessions were observed. Both the WL-S and WL-T tomato accessions revealed a high amount of ADH2, which indicates an intensive alcohol fermentation pathway during the first exposure to hypoxia. In comparison to the tolerant one, the expression of the adh2 gene was about two times higher for the sensitive tomato. Immunohistochemical analysis confirmed the presence of ADH in the parenchyma cells of the cortex and vascular tissue. During the second hypoxia stress, the sensitive accession showed a decreased accumulation of ADH protein and similar expression of the adh2 gene in comparison to the tolerant accession. Additionally, the proteome showed a greater protein abundance of glyceraldehyde-3-phosphate dehydrogenase in primed WL-S tomato. This could suggest that the sensitive tomato overcomes the oxygen limitation and adapts by reducing alcohol fermentation, which is toxic to plants because of the production of ethanol, and by enhancing glycolysis. Proteins detected in abundance in the sensitive accession are proposed as crucial factors for hypoxia stress priming and their function in hypoxia tolerance is discussed.
Highlights
Agriculture around the world is vulnerable to adverse weather events connected with climate change, characterized by extreme temperatures and intensive rainfall
We found that the experimental conditions could be divided into two large clusters in a dendrogram for both tomatoes; for PZ 215, cluster 6 (Ctrl, Rec and 1xH) and cluster 7 consisted of only 2xH (Figure 2A), while for POL 7/15, this was cluster 5 (Ctrl, Rec) and cluster 6 (1xH and 2xH) (Figure 2B)
The vast majority of papers concerning dehydrogenase enzyme immunodetection in plants are focused on cinnamyl alcohol dehydrogenase (CAD), which is involved in the lignification pathway [79]
Summary
Agriculture around the world is vulnerable to adverse weather events connected with climate change, characterized by extreme temperatures and intensive rainfall. This causes abiotic stresses, such as flooding or waterlogging, which affect the plants. Flooded soil leads to a decrease in oxygen concentration around the plant roots. Due to their sessile nature, plants are not able to escape from any stress factor, including waterlogging. To survive waterlogging, plants must regenerate NADP+ and NAD+, the molecules needed for glycolysis This is made possible via the alcohol fermentation pathway and the reduction of acetaldehyde to ethanol catalyzed with alcohol dehydrogenase (ADH) [1,5]. ADH plays a central role in anaerobic metabolism and has been observed to be one of the proteins synthesized under hypoxia conditions in maize and rice [6]
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