Impact of Climate Change on Regulation of Genes Involved in Sex Determination and Fruit Production in Cucumber

Confirmation of the unexpected occurrence of bitterness-inducing cucurbitacins in edible unripe melons by a two-step workflow based on liquid chromatography with combined UV and high-resolution MS detection

Plant metabolites known as cucurbitacins are known to impart an unpleasant bitter taste to edible fruits and even lead to severe health complications after the ingestion of relatively high amounts. In this study, an analytical method based on reversed phase liquid chromatography with combined detection by UV spectroscopy and atmospheric pressure chemical ionization high-resolution single/tandem mass spectrometry was applied to confirm the occurrence of four cucurbitacins (B, D, and R, and 23,24-dihydro cucurbitacin B) previously inferred in unexpectedly bitter-tasting fruits of an Italian variety (Scopatizzo) of unripe melon (Cucumis melo L.), known for the sweetness of its fruits. The method also unveiled the occurrence of eleven different cucurbitacins in not edible fruits of "exploding (squirting) cucumber" (Ecballium Elaterium L.), a well-known natural source of cucurbitacins. The unexpected occurrence of cucurbitacins in Scopatizzo fruits warrants further investigation into the factors triggering their biosynthesis, to help preventing both economic losses for farmers and potential health risks for consumers.

Revisit and explore the ethylene-independent mechanism of sex expression in cucumber (Cucumis sativus)

KEY MESSAGE

This review provides a thorough and comprehensive perspective on the topic of cucumber sexual expression. Specifically, insights into sex expression mediated by pathways other than ethylene are highlighted. Cucumber (Cucumis sativus L.) is a common and important commercial crop that is cultivated and consumed worldwide. Additionally, this species is commonly used as a model for investigating plant sex expression. Cucumbers exhibit a variety of floral arrangements, comprising male, female, and hermaphroditic (bisexual) flowers. Generally, cucumber plants that produce female flowers are typically preferred due to their significant impact on the overall output. Various environmental conditions, such as temperature, light quality, and photoperiod, have been also shown to influence the sex expression in this species. Multiple lines of evidence indicate that ethylene and its biosynthesis genes are crucial in regulating cucumber sex expression. Gibberellins, another well-known phytohormone, can similarly influence cucumber sex expression via an ethylene-independent route. Further studies employing the next-generation sequencing technology also visualized a deeper slice of the molecular mechanism such as the role of the cell cycle program in the cucumber sex expression. This review aims to provide an overview of the sex expression of cucumber including its underlying molecular mechanism and regulatory aspects based on recent investigations.

Genetic Insights and Molecular Breeding Approaches for Downy Mildew Resistance in Cucumber (Cucumis sativus L.): Current Progress and Future Prospects

Cucurbit downy mildew, caused by Pseudoperonospora cubensis, is a devastating disease in cucumbers that leads to significant yield losses in many cucurbit-growing regions worldwide. Developing resistant cucumber varieties is a sustainable approach to managing this disease, especially given the limitations of chemical control and the evolving nature of pathogens. This article reviews the genetic basis of downy mildew resistance in cucumbers, emphasizing key resistance (R) genes and quantitative trait loci (QTLs) that have been mapped. Recent advances in molecular breeding tools, including marker-assisted selection (MAS), genomic selection (GS), and CRISPR/Cas9 genome editing, have accelerated the development of resistant cultivars. This review also explores the role of transcriptomics, genomics, and other 'omics' technologies in unraveling the molecular mechanisms behind resistance and offers insights into the future of breeding strategies aimed at long-term disease management. Management strategies for cucurbit downy mildew are discussed, along with the potential impacts of climate change on the occurrence and severity of downy mildew, highlighting how changing environmental conditions may influence disease dynamics. Integrating these advanced genetic approaches with traditional breeding promises to accelerate the development of downy mildew-resistant cucumber varieties, contributing to the sustainability and resilience of cucumber production.

Increasing the productivity and quality of cucumber crop by improving the performance of the evaporative cooling system

Evaporative cooling in the kingdom of Saudi Arabia is one of the most important cooling systems used inside greenhouses to obtain an acceptable temperature change in hot, dry climates. It is considered insufficient during very hot summer periods, when temperatures outside the greenhouse reach approximately 48 °C, which affects the efficiency of cooling, and thus, creates stress on the plants, leading to wilting and a decrease in the production rate. The cooling system is developed by making an insulated rectangular tunnel. The air comes out through vertical openings directly to the plants. The results of evaluating plant heat stress in the developed cooling system (DCS) showed an increase in the values of the photosynthesis rate, transpiration rate, carbon dioxide exchange, and stomatal conductance. The plants also appeared well in terms of the shape of the leaves, their freshness, the abundance of flowers, and the large size of the fruits, while in the traditional cooling system (TCS) the plants exhibited some wilting and some brown spots. The hectare yield reached 42.49 ton/ha for the DCS system, while it reached 37.53 ton/ha for the TCS with an increasing rate of 13.22 %. The total weight of fruits harvested within 60 days of cultivation was 4.25 kg/m2 for the DCS and 3.75 kg/m2 for the TCS. The dry and fresh weight of fruit, stem, and leaves, total dissolved solids, vitamin C, chlorophyll percentage in leaves, and total plant acidity, were higher in DCS compared to the TCS.

Recent Advances in the Application of Cucurbitacins as Anticancer Agents

Cucurbitacins are tetracyclic triterpenoid secondary metabolites, widely distributed in the Cucurbitaceae family. These bitter-tasting compounds act primarily as defense mechanisms against external injuries, and thus against herbivores, and furthermore, they have also found use in folk medicine in the treatment of various diseases. Many studies have acknowledged significant biological activities of cucurbitacins, such as antioxidant and anti-inflammatory activities, antimicrobial properties, or antitumor potential. Overall, cucurbitacins have the ability to inhibit cell proliferation and induce apoptosis in various cancer cell lines. Both in vitro and in vivo studies were performed to evaluate the anticancer activity of varied cucurbitacins. Cucurbitacins offer a promising avenue for future cancer treatment strategies, and their diverse mechanisms of action make them attractive candidates for further investigation. The aim of the present study is to shed light on the chemical diversity of this group of compounds by providing the sources of origin of selected compounds and their chemical structure, as well as insight into their anticancer potential. In addition, within this paper molecular targets for cucurbitacins and signalling pathways important for cancer cell proliferation and/or survival that are affected by the described class of compounds have been presented.