Peptide Transporters in the Primary Gastrointestinal Tract of Pre-Feeding Mozambique Tilapia Larva.

Pazit Con,Tatiana Slosman,Tali Nitzan,Avner Cnaani,Sheenan Harpaz

doi:10.3389/fphys.2019.00808

Pazit Con, Tatiana Slosman + Show 3 more

Open Access

https://doi.org/10.3389/fphys.2019.00808

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Abstract

Fish larvae differ greatly from the adult form in their morphology and organ functionality. The functionality of the gastrointestinal tract depends on the expression of various pumps, transporters, and channels responsible for feed digestion and nutrients absorption. During the larval period, the gastrointestinal tract develops from a simple closed tube, into its complex form with differentiated segments, crypts and villi, as found in the adult. In this study, we characterized the expression of three peptide transporters (PepT1a, PepT1b, and PepT2) in the gastrointestinal tract of Mozambique tilapia (Oreochromis mossambicus) larvae along 12 days of development, from pre-hatching to the completion of yolk sac absorption. Gene expression analysis revealed differential and complimentary time-dependent expression of the PepT1 variants and PepT2 along the larval development period. Immunofluorescence analysis showed differential protein localization of the three peptide transporters (PepTs) along the gastrointestinal tract, in a similar pattern to the adult. In addition, PepT1a was localized in mucosal cells in the larvae esophagus, in much higher abundance than in the adults. The results of this study demonstrate specialization of intestinal sections and absorbance potential of the enterocytes prior to the onset of active exogenous feeding, thus pointing to an uncharacterized function and role of the gastrointestinal tract and its transporters during the larval period.

Highlights

The development of the gastrointestinal tract during larval stages has been studied in many fish species, such as European sea bass (Dicentrarchus labrax) (García Hernández et al, 2001; Sucré et al, 2009), Senegalese sole (Solea senegalensis) (Ribeiro et al, 1999), Mozambique tilapia (Oreochromis mossambicus) (Lo and Weng, 2006), Nile tilapia (Oreochromis niloticus) (Tengjaroenkul et al, 2000, 2002), gilthead seabream (Sparus aurata) (Sarasquete et al, 1995; Elbal et al, 2004; Mata-Sotres et al, 2016), Atlantic cod (Gadus morhua) (Kjorsvik et al, 1991), California halibut (Paralichthys californicus) (Gisbert et al, 2004), and Summer flounder (Paralichthys dentatus) (Bisbal and Bengtson, 1995)
There are few studies addressing these transporters at the larval and juvenile stages. As these transporters were shown to have an important role in protein absorption, the aim of this study was to characterize them in the early stages of the Mozambique tilapia gastrointestinal development
(p < 0.0001), while PepT2 expression was detected in the middle intestine (MI) and posterior intestine (PI) segments

Summary

Introduction

The development of the gastrointestinal tract during larval stages has been studied in many fish species, such as European sea bass (Dicentrarchus labrax) (García Hernández et al, 2001; Sucré et al, 2009), Senegalese sole (Solea senegalensis) (Ribeiro et al, 1999), Mozambique tilapia (Oreochromis mossambicus) (Lo and Weng, 2006), Nile tilapia (Oreochromis niloticus) (Tengjaroenkul et al, 2000, 2002), gilthead seabream (Sparus aurata) (Sarasquete et al, 1995; Elbal et al, 2004; Mata-Sotres et al, 2016), Atlantic cod (Gadus morhua) (Kjorsvik et al, 1991), California halibut (Paralichthys californicus) (Gisbert et al, 2004), and Summer flounder (Paralichthys dentatus) (Bisbal and Bengtson, 1995). Studies focused mostly on morphological description, while in recent years, studies have explored gene expression and regulation. While many different species have been studied, there are great species-specific. Peptide Transporters in the Pre-Feeding Tilapia Larva differences in feeding and digestive ontogeny even within the same family (Rønnestad et al, 2013). The zebrafish (Danio rerio) has been established as a model organism for various developmental studies. When addressing feeding and nutritional physiology, this species is not an ideal model (Ribas and Piferrer, 2014). The zebrafish lack a stomach, which changes the digestion and absorption processes that occur during feeding. There is a need to explore and advance our knowledge in other species

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