Persistent hypoxia can cause pulmonary arterial hypertension that may be associated with significant remodeling of the pulmonary arteries, including smooth muscle cell proliferation and hypertrophy. We previously demonstrated that the NADPH oxidase homolog NOX4 mediates human pulmonary artery smooth muscle cell (HPASMC) proliferation by transforming growth factor-beta1 (TGF-beta1). We now show that hypoxia increases HPASMC proliferation in vitro, accompanied by increased reactive oxygen species generation and NOX4 gene expression, and is inhibited by antioxidants, the flavoenzyme inhibitor diphenyleneiodonium (DPI), and NOX4 gene silencing. HPASMC proliferation and NOX4 expression are also observed when media from hypoxic HPASMC are added to HPASMC grown in normoxic conditions, suggesting autocrine stimulation. TGF-beta1 and insulin-like growth factor binding protein-3 (IGFBP-3) are both increased in the media of hypoxic HPASMC, and increased IGFBP-3 gene expression is noted in hypoxic HPASMC. Treatment with anti-TGF-beta1 antibody attenuates NOX4 and IGFBP-3 gene expression, accumulation of IGFBP-3 protein in media, and proliferation. Inhibition of IGFBP-3 expression with small interfering RNA (siRNA) decreases NOX4 gene expression and hypoxic proliferation. Conversely, NOX4 silencing does not decrease hypoxic IGFBP-3 gene expression or secreted protein. Smad inhibition does not but the phosphatidylinositol 3-kinase (PI3K) signaling pathway inhibitor LY-294002 does inhibit NOX4 and IGFBP-3 gene expression, IGFBP-3 secretion, and cellular proliferation resulting from hypoxia. Immunoblots from hypoxic HPASMC reveal increased TGF-beta1-mediated phosphorylation of the serine/threonine kinase (Akt), consistent with hypoxia-induced activation of PI3K/Akt signaling pathways to promote proliferation. We conclude that hypoxic HPASMC produce TGF-beta1 that acts in an autocrine fashion to induce IGFBP-3 through PI3K/Akt. IGFBP-3 increases NOX4 gene expression, resulting in HPASMC proliferation. These observations add to our understanding hypoxic pulmonary vascular remodeling.
This study evaluates the potential for adaptability and tolerance of wheat genotypes (G) to an arid environment. We examined the influence of drought stress (DS) (100, 75, and 50% field capacity), planting times (PT) (16-November, 01-December, 16-December and 01-January), and G (Yocoro Rojo, FKAU-10, Faisalabad-08, and Galaxy L-7096) on phenological development, growth indices, grain yield, and water use efficiency of drip-irrigated wheat. Development measured at five phenological growth stages (GS) (tillering, jointing, booting, heading, and maturity) and growth indices 30, 45, 60, and 75 days after sowing (DAS) were also correlated with final grain yield. Tillering occurred earlier in DS plots, to a maximum of 31 days. Days to complete 50% heading and physiological crop maturity were the most susceptible GS that denoted 31–72% reduction in number of days to complete these GS at severe DS. Wheat G grown with severe DS had the shortest grain filling duration. Genotype Fsd-08 presented greater adaptability to studied arid climate and recorded 31, 35, and 38% longer grain filling period as compared with rest of the G at 100–50% field capacity respectively. December sowing mitigated the drought and delayed planting effects by producing superior growth and yield (2162 kg ha−1) at severe DS. Genotypes Fsd-08 and L-7096 attained the minimum plant height (36 cm) and the shortest growth cycle (76 days) for January planting with 50% field capacity. At severe DS leaf area index, dry matter accumulation, crop growth rate and net assimilation rate were decreased by 67, 57, 34, and 38% as compared to non-stressed plots. Genotypes Fsd-08 and F-10 were the superior ones and secured 14–17% higher grain yield than genotype YR for severely stressed plots. The correlation between crop growth indices and grain yield depicted the highest value (0.58–0.71) at 60–75 DAS. So the major contribution of these growth indices toward grain yield was at the start of reproductive phase. It's clear that booting and grain filling are the most sensitive GS that are severely affected by both drought and delay in planting.
A field experiment studying the effect of water stress on alfalfa (Medicago sativa) productivity and water use efficiency was conducted at the Agricultural Experimental Station of King Abdelaziz University. The design of the experiment was randomized complete block design (RCBD) with four replicates. It consisted of three treatments, namely: field capacity treatment (FC) as a control, 85% FC and 70% FC as stress treatments. The irrigation water for all treatments was precisely supplied using recent technology known as the water electronics module (WEM).Results indicated that decreasing water supply decreased fresh and dry yield of alfalfa but increased irrigation water use efficiency (IWUE). As a result, 13 and 27% of irrigation water were saved from 85% FC and 70% FC treatments respectively in each cut compared with the FC treatment. The reduction of water supply resulted in a yield reduction of 12 and 21.7% for 85% FC and 70% FC, respectively. The results also proved that WEM is a practical tool to precisely supply irrigation water and can be used effectively to control deficit irrigation. RÉSUMÉUne expérience sur le terrain a été réalisée à la station expérimentale agricole de l'Université du Roi Abdelaziz pour étudier l'effet du stress hydrique sur la luzerne (Medicago sativa), sa productivité et son efficience d'utilisation de l'eau. La conception de l'expérience était en blocs aléatoires complets (CR) avec quatre répétitions. Elle se composait de trois traitements à savoir: le traitement en irrigation à la capacité au champ (FC) comme témoin, par comparaison aux traitements de stress à FC 85% et FC 70%, respectivement. L'eau d'irrigation pour tous les traitements a été ajustée précisément en utilisant la technologie récente connue sous le nom de 'water electronics module' (WEM).Les résultats indiquent que l'approvisionnement en eau diminue les rendements frais et sec de la luzerne, mais augmente l'efficacité d'utilisation d'eau d'irrigation (IWUE). En conséquence, 13 et 27% de l'eau d'irrigation ont été épargnés par les traitements FC 85% et 70% respectivement dans chaque coupe. La réduction de l'approvisionnement en eau a entraîné une baisse de rendement de 12 et de 21,7% pour les FC et le FC 85% à 70%, respectivement. Les résultats ont également montré que WEM est un outil pratique pour fournir l'eau d'irrigation précisément et peuvent être utilisés efficacement pour contrôler l'irrigation déficitaire.
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