Person: Buezo Bravo, Javier
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Buezo Bravo
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Javier
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Ciencias
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IMAB. Research Institute for Multidisciplinary Applied Biology
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0000-0002-6287-1587
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811160
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Publication Embargo A new oxidative pathway of nitric oxide production from oximes in plants(Cell Press, 2024) LĆ³pez GĆ³mez, Pedro; Buezo Bravo, Javier; Urra RodrĆguez, Marina; Cornejo Ibergallartu, Alfonso; Esteban Terradillos, Raquel; FernĆ”ndez de los Reyes, Jorge; Urarte RodrĆguez, EstĆbaliz; RodrĆguez-Dobreva, EstefanĆa; Chamizo Ampudia, Alejandro; Eguaras, Alejandro; Wolf, Sebastian; Marino Bilbao, Daniel; MartĆnez Merino, VĆctor; MorĆ”n Juez, JosĆ© Fernando; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Institute for Advanced Materials and Mathematics - INAMAT2Nitric oxide (NO) is an essential reactive oxygen species and a signal molecule in plants. Although several studies have proposed the occurrence of oxidative NO production, only reductive routes for NO production, such as the nitrate (NO-3) -upper-reductase pathway, have been evidenced to date in land plants. However, plants grown axenically with ammonium as the sole source of nitrogen exhibit contents of nitrite and NO3, evidencing the existence of a metabolic pathway for oxidative production of NO. We hypothesized that ox- imes, such as indole-3-acetaldoxime (IAOx), a precursor to indole-3-acetic acid, are intermediate oxidation products in NO synthesis. We detected the production of NO from IAOx and other oximes catalyzed by peroxidase (POD) enzyme using both 4-amino-5-methylamino-20,70-difluorescein fluorescence and chem- iluminescence. Flavins stimulated the reaction, while superoxide dismutase inhibited it. Interestingly, mouse NO synthase can also use IAOx to produce NO at a lower rate than POD. We provided a full mech- anism for POD-dependent NO production from IAOx consistent with the experimental data and supported by density functional theory calculations. We showed that the addition of IAOx to extracts from Medicago truncatula increased the in vitro production of NO, while in vivo supplementation of IAOx and other oximes increased the number of lateral roots, as shown for NO donors, and a more than 10-fold increase in IAOx dehydratase expression. Furthermore, we found that in vivo supplementation of IAOx increased NO pro- duction in Arabidopsis thaliana wild-type plants, while prx33-34 mutant plants, defective in POD33-34, had reduced production. Our data show that the release of NO by IAOx, as well as its auxinic effect, explain the superroot phenotype. Collectively, our study reveals that plants produce NO utilizing diverse molecules such as oximes, POD, and flavins, which are widely distributed in the plant kingdom, thus intro- ducing a long-awaited oxidative pathway to NO production in plants. This knowledge has essential impli- cations for understanding signaling in biological systems.Publication Open Access The importance of the urea cycle and its relationships to polyamine metabolism during ammonium stress in Medicago truncatula(Oxford University Press, 2022) Urra RodrĆguez, Marina; Buezo Bravo, Javier; Royo Castillejo, Beatriz; Cornejo Ibergallartu, Alfonso; LĆ³pez GĆ³mez, Pedro; CerdĆ”n Ruiz, Daniel; Esteban Terradillos, Raquel; MartĆnez Merino, VĆctor; Gogorcena, Yolanda; Tavladoraki, Paraskevi; MorĆ”n Juez, JosĆ© Fernando; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Institute for Multidisciplinary Research in Applied Biology - IMAB; Ciencias; Universidad PĆŗblica de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako GobernuarenThe ornithineāurea cycle (urea cycle) makes a signifcant contribution to the metabolic responses of lower photosynthetic eukaryotes to episodes of high nitrogen availability. In this study, we compared the role of the plant urea cycle and its relationships to polyamine metabolism in ammonium-fed and nitrate-fed Medicago truncatula plants. High ammonium resulted in the accumulation of ammonium and pathway intermediates, particularly glutamine, arginine, ornithine, and putrescine. Arginine decarboxylase activity was decreased in roots, suggesting that the ornithine decarboxylase-dependent production of putrescine was important in situations of ammonium stress. The activity of copper amine oxidase, which releases ammonium from putrescine, was signifcantly decreased in both shoots and roots. In addition, physiological concentrations of ammonium inhibited copper amine oxidase activity in in vitro assays, supporting the conclusion that high ammonium accumulation favors putrescine synthesis. Moreover, early supplementation of plants with putrescine avoided ammonium toxicity. The levels of transcripts encoding urea-cyclerelated proteins were increased and transcripts involved in polyamine catabolism were decreased under high ammonium concentrations. We conclude that the urea cycle and associated polyamine metabolism function as important protective mechanisms limiting ammonium toxicity in M. truncatula. These fndings demonstrate the relevance of the urea cycle to polyamine metabolism in higher plants.Publication Embargo Downed woody debris carbon emissions in a European temperate virgin forest as driven by species, decay classes, diameter and microclimate(Elsevier, 2024) Buezo Bravo, Javier; Medina, Nagore G.; HereÅ, Ana-Maria; Petritan, Ion C.; Cornelissen, Johannes H.C.; Petritan, Any Mary; Esteban Terradillos, Raquel; Ilinca, Elisabeth; Stoian, R.; Curiel Yuste, Jorge; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMABDowned woody debris (DWD) plays an important role as regulator of nutrient and carbon (C) cycling in forests, accounting for up to the 20 % of the total C stocks in primary forests. DWD persistence is highly influenced by microbial decomposition, which is determined by various environmental factors, including fluctuations in temperature and moisture, as well as in intrinsic DWD properties determined by species, diameter, or decay classes (DCs). The relative importance of these different drivers, as well as their interactions, remains largely unknown. Moreover, the importance of DWD for C cycling in virgin forests remains poorly understood, due to their scarcity and poor accessibility. To address this research gap, we conducted a study on DWD respiration (RDWD), in a temperate virgin forest dominated by European beech and silver fir. Our investigation analysed the correlation between RDWD of these two dominant tree species and the seasonal changes in climate (temperature and moisture), considering other intrinsic DWD traits such as DCs (1, 2 and 4) and diameters (1, 10 and 25 cm). As anticipated, RDWD (normalized per gram of dry DWD) increased with air temperature. Surprisingly, DWD diameter also had a strong positive correlation with R DWD. Nonetheless, the sensitivity to both variables and other intrinsic traits (DC and density) was greatly modulated by the species. On the contrary, water content, which exhibited a considerable spatial variation, had an overall negative effect on R DWD. Virgin forests are generally seen as ineffective C sinks due to their lack of net productivity and high respiration and nutrient turnover. However, the rates of R DWD in this virgin forest were significantly lower than those previously estimated for managed forests. This suggests that DWD in virgin forests may be bufferingforest CO2 emissions to the atmosphere more than previously thought.