SUMMARY
The Arabidopsis thaliana aldehyde oxidase 3 (AAO3) catalyzes the oxidation of abscisic aldehyde (ABal) to abscisic acid (ABA). Besides ABal, plants generate other aldehydes that can be toxic above a certain threshold. AAO3 knockout mutants (aao3) exhibited earlier senescence but equivalent relative water content compared with wild‐type (WT) during normal growth or upon application of UV‐C irradiation. Aldehyde profiling in leaves of 24‐day‐old plants revealed higher accumulation of acrolein, crotonaldehyde, 3Z‐hexenal, hexanal and acetaldehyde in aao3 mutants compared with WT leaves. Similarly, higher levels of acrolein, benzaldehyde, crotonaldehyde, propionaldehyde, trans‐2‐hexenal and acetaldehyde were accumulated in aao3 mutants upon UV‐C irradiation. Aldehydes application to plants hastened profuse senescence symptoms and higher accumulation of aldehydes, such as acrolein, benzaldehyde and 4‐hydroxy‐2‐nonenal, in aao3 mutant leaves as compared with WT. The senescence symptoms included greater decrease in chlorophyll content and increase in transcript expression of the early senescence marker genes, Senescence‐Related‐Gene1, Stay‐Green‐Protein2 as well as NAC‐LIKE, ACTIVATED‐BY AP3/P1. Notably, although aao3 had lower ABA content than WT, members of the ABA‐responding genes SnRKs were expressed at similar levels in aao3 and WT. Moreover, the other ABA‐deficient mutants [aba2 and 9‐cis‐poxycarotenoid dioxygenase3‐2 (nced3‐2), that has functional AAO3] exhibited similar aldehydes accumulation and chlorophyll content like WT under normal growth conditions or UV‐C irradiation. These results indicate that the absence of AAO3 oxidation activity and not the lower ABA and its associated function is responsible for the earlier senescence symptoms in aao3 mutant.
Halophytic plants are, by definition, well adapted to saline soils. However, even halophytes can face nutritional imbalance and the accumulation of high levels of compounds such as oxalic acid (OA), and nitrate (NO3−). These compounds compromise the potential nutritional health benefits associated with salt-tolerant plants such as Portulaca oleracea or Purslane. Purslane has long been known to be a highly nutritious leafy vegetable particularly with respect to high levels of omega-3 fatty acids. Thus, preventing the accumulation of non-nutritional compounds will allow plants to be grown in saline conditions as crops. Two ecotypes (ET and RN) of Portulaca oleracea plants were grown under growth room conditions with two levels of salinity (0, 50 mM NaCl) and three ratios of nitrate: ammonium (0:100%; 33:66%; 25:75% NO3−:NH4+). The results show that both ecotypes, when exposed to elevated NO3−, showed severe leaf chlorosis, high levels of OA, citric acid, and malic acid. Compared to ecotype RN, ecotype ET, exposed to elevated NH4+ concentrations (33% and 75%) and 50 mM NaCl, displayed a marked reduction in OA content, increased total chlorophyll and carotenoid contents, crude protein content, total fatty acid (TFA) and α-Linolenic acid (ALA), enhancing leaf quality. This opens the potential to grow high biomass, low OA P. oleracae crops. Lastly, our experiments suggest that ecotype ET copes with saline conditions and elevated NH4+ through shifts in leaf metabolites.
Sarcocornia A. J. Scott is a halophytic edible succulent plant belonging to the Amaranthaceae family. To date, the genus includes 28 species distributed worldwide in saline environments, usually salt marshes. Sarcocornia (Scott) is similar to Salicornia (L.), which has a recognized commercial value in morphological and taxonomical traits. Species of both genera are commonly named samphire or glassworts in Europe, and their fleshy shoots are commercialized under their traditional names. Due to their nutritional, organoleptic and medicinal properties, Sarcocornia species have a high economic potential in various biotechnology sectors. Being highly tolerant to salt, they can be cultivated in saline conditions, and dissimilar to Salicornia, they are perennial, i.e., they can be harvested year-round. Therefore, Sarcocornia species are considered promising gourmet vegetables to be explored in the context of climate change, soil and water salinization and eco-sustainability. We hereby put together and reviewed the most relevant information on Sarcocornia taxonomy, morphology, nutritional and pharmacological properties, uses in ethnomedicine, potential applications in biotechnology, and propagation strategies.
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