Browsing by Author "Khan, Arzoo"

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    A STUDY ON MOLECULAR RESPONSES OF HYPOXIA EXPOSURE IN GOLDEN MAHSEER, Tor putitora (HAMILTON, 1822)
    (G.B. Pant University of Agriculture and Technology, Pantnagar-263145, 2023-10-01) Khan, Arzoo; Kumar, Avdesh
    Golden mahseer is an important food and recreational species of Indian Himalayan region and also declared as an endangered species. The present study aimed to observe the behavioural, metabolic and molecular response of golden mahseer to acute hypoxia. The fishes were exposed to 96 hour of hypoxia stress. Different parameters related to behavioral and metabolic responses were documented. The molecular response was studied by qRTPCR assay of 12 hypoxia responsive genes hif1ab, hif2a, hif3a, aldoaa, vegfaa, vegfab, ldhb1, igfbp-1, igfbp-2a, igfbp-3, epoa, hmox2a. Under hypoxia stress fish showed behavioural responses in terms of aerial emergence, rapid gulping, circular swimming, wide-mouth gape, settling at the bottom corner and rapid tail movement. The gill ventilation rate increased with decreasing dissolved oxygen level that indicated that the fishes equilibrate the oxygen pressure in the blood with the oxygen pressure in the surrounding water. The mass specific consumption rate of oxygen significantly decreased which showed the metabolic response under low oxygen availability. The distinctive expression pattern of hif2a and hif3a mRNA indicated its role in adaptive response to tissue hypoxia. Among the vascular endothelial growth factor genes the enhanced expression of vegfab across all examined tissue of Tor putitora suggests its role in the adaptation to acute hypoxic stress. Among different igfbp’s only igfbp1 have shown enhanced expression in different tissues while igfbp2a and igfbp3a did not expressed under hypoxic condition. The detection of only one isoform (igfbp1) of golden mahseer suggested that it predominantly regulate the igfbp function in this species. The up-regulation of erythropoietin a (epoa) gene in different tissue of Tor putitora suggests its role in haemoglobin oxygen affinity in maintaining the haemoglobin saturation under falling blood oxygen level conditions. The heme oxygenase 2 alpha (hmox2a) expression in different tissue under hypoxic condition suggested its role in iron homeostasis under stress condition. The ldhb1 and aldoaa are metabolic genes which are involved in glycolytic pathway. The up-regulation of ldhb1 and aldoaa is indicative of activation of anaerobic glycolysis in response to hypoxic stress as an adaptation mechanism under low oxygen availability. The present study provides valuable information regarding the molecular response of different genes to hypoxia stress in golden mahseer. These genes can also be used as the biomarkers of ecosystem hypoxia stress.