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Background/Aims: Excess maternal salt intake during pregnancy may alter fetal development. However; our knowledge on how an increased salt intake during pregnancy influences fetal eye development is limited. In this study, we investigated the effects of high salt treatment on the developing eyes in chick embryos, especially focusing on the development of the retina and the lens. Methods: 5.5 day chick embryos were exposed to 280mosm/l (n=17), or 300mosm/l (n=16) NaCl. The treated embryos were then incubated for 96 hours before they were fixed with 4% paraformaldehyde for H&E staining, whole mount embryo immunostaining and TUNEL staining. BrdU and PH3 incorporation experiments were performed on the chick embryos after high salt treatment. RT-PCR analyses were conducted from chick retina tissues. Results: We demonstrated that high-salt treatment altered the size of eyes in chick embryos, induced malformation of the eyes and impaired the development of the lens and the retina. We found an impaired expression of Paired box 6 (PAX6) and neuronal cells in the developing retina as revealed by neurofilament immunofluorescent staining. There was a reduction in the number of BrdU-positive cells and PH3-positive cells in the retina, indicating an impaired cell proliferation with high salt treatment. High salt treatment also resulted in an increased number of TUNEL-positive cells in the retina, indicating a higher amount of cell death. RT-PCR data displayed that the expression of the pro-apoptotic molecule nerve growth factor (NGF) in chick retina was increased and CyclinD1 was reduced with high-salt treatment. The size of the lens was reduced and Pax6 expression in the lens was significantly inhibited. High salt treatment was detrimental to the migration of neural crest cells. Conclusion: Taken together; our study demonstrated that high salt exposure of 5.5 day chick embryos led to an impairment of retina and lens development, possibly through interfering with Pax6 expression.
Membrane sterol composition in Arabidopsis thaliana affects root elongation via auxin biosynthesis
(2021)
Plant membrane sterol composition has been reported to affect growth and gravitropism via polar auxin transport and auxin signaling. However, as to whether sterols influence auxin biosynthesis has received little attention. Here, by using the sterol biosynthesis mutant cyclopropylsterol isomerase1-1 (cpi1-1) and sterol application, we reveal that cycloeucalenol, a CPI1 substrate, and sitosterol, an end-product of sterol biosynthesis, antagonistically affect auxin biosynthesis. The short root phenotype of cpi1-1 was associated with a markedly enhanced auxin response in the root tip. Both were neither suppressed by mutations in polar auxin transport (PAT) proteins nor by treatment with a PAT inhibitor and responded to an auxin signaling inhibitor. However, expression of several auxin biosynthesis genes TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 (TAA1) was upregulated in cpi1-1. Functionally, TAA1 mutation reduced the auxin response in cpi1-1 and partially rescued its short root phenotype. In support of this genetic evidence, application of cycloeucalenol upregulated expression of the auxin responsive reporter DR5:GUS (beta-glucuronidase) and of several auxin biosynthesis genes, while sitosterol repressed their expression. Hence, our combined genetic, pharmacological, and sterol application studies reveal a hitherto unexplored sterol-dependent modulation of auxin biosynthesis during Arabidopsis root elongation.