Differential Responses of Water Uptake Pathways and Expression of Two Aquaporin Genes to Water-Deficit in Rice Seedlings of Two Genotypes

Water-deficit （WD） is a major abiotic stress constraining crop productivity worldwide. Zhenshan 97 is a drought-susceptible rice genotype, while IRAT109 is a drought-resistant one. However, the physiological basis of the difference remains unclear. These two genotypes had similar total water uptake rates under both WD and well-watered （WW） conditions, and their water uptake rates under WD were significantly decreased compared with those under WW. However, the water uptake rate via the cell-to-cell pathway was significantly increased in Zhenshan 97 but decreased in IRAT109 under WD, whereas the opposite trends were observed through the apoplastic pathway. These results indicated that the stress responses and relative contributions of these two water uptake pathways were associated with rice genotype under WD. The expression levels of OsPIP2;4 and OsPIP2;5 genes were significantly higher in roots of Zhenshan 97 than in IRAT109 under the two conditions. OsPIP2;4 expression in roots was significantly up-regulated under WD, while OsPIP2;5 expression showed no significant change. These results suggest that the expression levels of OsPIP2;4 and OsPIP2;5 in rice are dependent on genotype and water availability. Compared with Zhenshan 97, IRAT109 had a higher root dry weight, water uptake rate and xylem sap flow rate, and lower leaf water potential and root porosity under WD, which might be responsible for the drought resistance in IRAT109.

Expression of aquaporin-1 in the human peritoneum and the effect of peritoneal dialysis on its expression

Objective To investigate the expression of aquaporin-1 (AQP1) in the human peritoneum and to evaluate the effect of peritoneal dialysis (PD) on its expression.Methods Peritoneal biopsies were obtained from normal subjects (n =10), uremic nondialysis patients (n = 12) at catheter insertion and PD patients ( n = 10) at the time of catheter removal, reinsertion or renal transplantation. Western blot, immuno-histochemical staining and reverse transcript-polymerase chain reaction ( RT-PCR) techniques were used to investigate AQP1 expression.Results All peritoneal samples expressed AQP1 at both mRNA and protein levels. Western blot revealed a major band at 28 kD as well as more diffuse bands between 35 and 50 kD. The 28 kD band represents the nonglycosylated form of the protein while the 35 - 50 kD bands correspond to glycosylated AQP1. Immunohistochemical staining found the positive deposits were distributed in the mesothelial cells, endothelial cells of capillaries, venules and small veins, whereas no signal was detected in the arterioles. Semi-quantitative analysis showed that AQP1 expression was remarkably stable in all samples, whatever their origin (P>0. 05).Conclusions Our findings suggested that AQP1 is the molecular counterpart of an ultra small pore during PD. Secondly, the peritoneal mesothelial cell might also be involved in peritoneal transcellular water transport. As regards whether or not the structural or distributional alterations of AQP1 in the peritoneum may be more obviously expressed during PD, further study is needed.

Histological,Ultrastructural,and Genetic Investigatory Comparison between Different Types of Experimentally-Induced Antemortem Burns

Background:Burn is a cutaneous injury that is caused by heat,electricity,chemicals,freezing,and radiation.Aims and Objectives:This study aimed to differentiate between dry heat burn injury and other common cutaneous burn injuries.Materials and Methods:For this,different types of dermal burns were created experimentally in four groups of rats,5 rats for each,as the following:dry heat burn model,scalding model,chemical burn model,and electrical burn model.The burnt skin and hair samples were subjected to scanning electron microscopic examination,molecular assay of aquaporin-3(AQP-3)gene expression,and histopathological investigation.Results:There were crakes,holes,and cuticular irregularity in hairs exposed to both dry heat and sulfuric acid(chemical burn),while the major lesion observed in hairs exposed to boiling water(scald injury)was cuticular cell loss.On the other hand,dry burnt skin showed empty orifices of the hair and sebaceous gland with overlapped smooth lamella,while scald induced irregularity of collagen fibers.The sulfuric acid produces separation of the epidermis from the dermis and irregularity in collagen fiber.Rat skin exposed to electric current appears with fissure,lacerated edges,and erected broken hairs.Despite AQP-3 gene expression was significantly upregulated in the burnt skin of all experimental models in comparing with control rats,dry heat burned skin showed the highest upregulated level.In addition,the coagulation of the dermoepidermal cells and vesicles formation were the most pronounced lesions observed in all types of burns,while scald was distinguished by appearance of elongated cellular nuclei.Conclusion:These observations suggest the possibility to differentiate between dry thermal burn,scald injury,chemical burn,and electrical burn using the combination between scanning electron microscopic examination,analysis of cutaneous AQP-3 gene expression,and histological investigation.