Lipoxygenase and Its Relationship with Ethylene During Ripening of Genetically Modified Tomato (Solanum lycopersicum)

Abstract

Research background. TomloxB is the main isoform of lipoxygenase associated with ripening and senescence of fruits. On the other hand, ethylene, a gaseous hormone, is essential for the regulation of ripening in climacteric fruits like tomatoes. However, the relationship between TomloxB and ethylene production has not been thoroughly studied. Therefore, we aim to assess the effect of exogenous ethylene in transgenic tomatoes that contain a silenced TomloxB gene, and subsequently evaluate lipoxygenase activity, 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production; as well as to quantify the expression of the genes encoding 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB.Experimental approach. To investigate the effect of lipoxygenase and 1-aminocyclopropane-1-carboxylic acid oxidase activity, fruits harvested at the stages of break, turning and pink were used. Tomatoes at break stage collected from transgenic and wild type plants were used to determine ethylene production and gene expression. Genetically modified and wild type tomato fruits were exposed to 100 μL/L exogenous ethylene. Lipoxygenase activity was measured spectrophotometrically. Activity of 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production were determined by gas chromatography. Oligonucleotides for differentially expressed genes: 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB were used to determine gene expression by real-time PCR.Results and conclusions. The data showed that silencing of TomloxB caused a reduction in lipoxygenase activity and ethylene production in tomato fruits, and also reduced 1-aminocyclopropane-1-carboxylic acid oxidase activity. Hence, the addition of exogenous ethylene increased lipoxygenase activity in all treatments and 1-aminocyclopropane-1-carboxylic acid oxidase activity only in transgenic lines at break stage, consequently there was a positive regulation between TomloxB and ethylene, as increasing the amount of ethylene increased the activity of lipoxygenase. The results suggest that lipoxygenase may be a regulator of 1-aminocyclopropane-1-carboxylic acid oxidase and production of ethylene at break stage.Novelty and scientific contribution. These results lead to a better understanding of the metabolic contribution of TomloxB in fruit ripening and how it is linked to the senescence-related process, which can lead to a longer shelf life of fruits. Understanding this relationship between lipoxygenase and ethylene can be useful for better post-harvest handling of tomatoes.

Effect of oxalic acid on postharvest life of tomato modified with the TomLoxB gene in anti-sense

“…In this experiment, a smaller weight loss of 8.5 % was obtained in GM fruits, with 3 mM at day 30. Here the synergistic effect is shown, between the afore mentioned mechanisms of action of OA and the silencing of TomLoxB gene, which decreased the production and expression of the same enzyme, preventing the fatty acids that constitute the membrane from being oxidized by the enzyme (Velázquez-López et al, 2020;León-García et al, 2017). This also contributed to maintaining lightness (L*) longer in GM-C (18 %) and GM-3mM (23 %) tomatoes at day 15 and GM-C (10 %) and GM-3mM (12 %) at day 30, compared to WT-C control fruits (36 L*, day 15; 34 L*, day 30).…”

“…Lipoxygenase (LOX) activity was assayed according to Velázquez-López et al (2020), using linoleic acid as substrate. Tomato juice was extracted and centrifuged for 5 min at 8765xg in an Eppendorf centrifuge model 5415R (Hamburg, Germany).…”

“…León-García et al (2017) silenced the TomLoxB gene in tomato (Solanum lycopersicum) fruits variety TA234, that resulted in increased firmness, reduced lipoxygenase activity and extended shelf life compared to control fruits. Studies have been conducted to learn about the physiology of the modified tomatoes (Velázquez-López et al, 2020;Mazón-Abarca et al, 2022a;Mazón-Abarca et al, 2022b); however, more work remains to be pursued. The objective of this study was to evaluate the response of tomato (Solanum lycopersicum) variety TA234 with silenced TomLoxB gene after the application of oxalic acid during ripening.…”

Ethylene: Management and breeding for postharvest quality in vegetable crops. A review

“…Another aspect that has been investigated in tomato is the correlation between ET action and membrane catabolic enzymes such as phospholipases ( Natalini et al., 2017 ) and lipoxygenase ( Velázquez-López et al., 2020 ). By silencing the main isoform of lipoxygenase encoding gene ( TomloxB ) it was possible to conclude that lipoxygenase could be a regulator of ET synthesis through the activity of the enzyme ACO.…”

“…By silencing the main isoform of lipoxygenase encoding gene ( TomloxB ) it was possible to conclude that lipoxygenase could be a regulator of ET synthesis through the activity of the enzyme ACO. The Authors suggested that this discover could be useful for improving the shelf-life extension and the postharvest management of tomato ( Velázquez-López et al., 2020 ).…”