At least two expressed genes for transcription factors Pitx2 and Rpx are present in 1 common carp and are upregulated during winter acclimatization. 2 3 4Kausel, G., Vera, T., Valenzuela, G., Lopez, M. ABSTRACT
26The mechanisms of seasonal acclimatization in eurythermal fish such as common 27 carp are not fully understood. Here, we concentrate on the regulation of pituitary 28 factors, as this organ was shown to be highly affected by seasonal changes. We 29 cloned and sequenced two different cDNAs for each of the transcription factors Pitx2 30and Rpx, known to play a role in pituitary development. We show that these genes 31 are conserved throughout evolution, to different degrees depending on the specific 32 domain considered. Finally, we show that the cDNAs for both factors are clearly up-33 regulated during the winter season, in sharp contrast to other regulators such as Pit1 34 or pituitary hormone genes such as prolactin (prl) and growth hormone (gh). Our 35 results suggest that increased expression of Pitx2 and Rpx contributes to seasonal 36 adaptation of common carp to winter conditions. 37
39Key words: Pitx2; Rpx; gene expression; carp fish; seasonal control; acclimatization; 40
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INTRODUCTION 42Eurythermal fish rearrange their molecular and cellular functions to compensate for 43 the circannual environmental seasonal changes of their habitat. This acclimatization 44 process occurs through a cyclical reprogramming of molecular processes, involving 45 in common carp (Cyprinus carpio) the modulation of transcriptional and translational 46 events in various tissues (Krauskopf et al., 1988; Figueroa et al., 1994; Goldspink et 47 al., 1995; Kausel et al., 1999; Molina et al., 2002). Likewise, although much less 48 complex than the process of acclimatization, long-term adaptation to different 49 temperatures also involves reprogramming of gene expression in different tissues 50 (Gracey et al., 2004), including carp pituitary gland (Figueroa et al., 1997; Arends et 51 al., 1998). In fish, the pituitary seems to function as a central node controlling the 52 adaptive compensatory response to stressors or environmental changes. Increased 53 expression of prolactin (Prl) mRNA, the most versatile pituitary hormone, occurs in 54 the rostral pars distalis (RPD) of summer-acclimatized carp, as compared to the 55 negligible level of transcription detected in winter-acclimatized fish (Figueroa et al., 56 1994). Photoperiod appears to be a particularly relevant factor for modulation of prl 57 transcription in carp (Figueroa et al., 1997). Another pituitary hormone of the Prl 58 family that is up-regulated during the summer season is growth hormone (Gh) 59 (Figueroa et al., 2005). In good correlation with these observations, expression of the 60 main regulator of these genes, the pituitary-specific transcription factor Pit1 is 61 strongly increased during acclimatization of the common carp (Cyprinus carpio) from 62 winter to summer (Kausel et al., 1999). 63During embryogenesis, various other transcription fac...
