Maternal mRNA input of growth and stress-response-related genes in cichlids in relation to egg size and trophic specialization

• Published in: EvoDevo Vol. 9; no. 1; pp. 23 - 17
• Main Authors: Ahi, Ehsan Pashay, Singh, Pooja, Lecaudey, Laurène Alicia, Gessl, Wolfgang, Sturmbauer, Christian
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 01.12.2018; BioMed Central; BMC
• Subjects: Abundance; Adaptation; Adaptive radiation; Animal behavior; Animal reproduction; Cichlidae; East African lakes; Eggs; Evolution & development; Fish; Gene expression; Growth hormone; Haplochromine cichlids; Insulin; Insulin-like growth factor II; Insulin-like growth factors; Lakes; Maternal mRNA; Morphogenesis; mRNA; Niches; Specialization; Species; Stress response; Trophic specialization; Variation; Lake Malawi; Lake Victoria; Lake Tanganyika; Adaptive radiation; East African lakes; Haplochromine cichlids; Trophic specialization; Eggs; Maternal mRNA
• ISSN: 2041-9139; 2041-9139
• DOI: 10.1186/s13227-018-0112-3

Egg size represents an important form of maternal effect determined by a complex interplay of long-term adaptation and short-term plasticity balancing egg size with brood size. Haplochromine cichlids are maternal mouthbrooders showing differential parental investment in different species, manifested in great variation in egg size, brood size and duration of maternal care. Little is known about maternally determined molecular characters of eggs in fishes and their relation to egg size and trophic specialization. Here we investigate maternal mRNA inputs of selected growth- and stress-related genes in eggs of mouthbrooding cichlid fishes adapted to different trophic niches from Lake Tanganyika, Lake Malawi, Lake Victoria and compare them to their riverine allies. We first identified two reference genes, and , to be suitable for cross-species quantification of mRNA abundance via qRT-PCR in the cichlid eggs. Using these reference genes, we found substantial variation in maternal mRNA input for a set of candidate genes related to growth and stress response across species and lakes. We observed negative correlation of mRNA abundance between two of growth hormone receptor paralogs ( and ) across all haplochromine cichlid species which also differentiate the species in the two younger lakes, Malawi and Lake Victoria, from those in Lake Tanganyika and ancestral riverine species. Furthermore, we found correlations between egg size and maternal mRNA abundance of two growth-related genes and across the haplochromine cichlids as well as distinct clustering of the species based on their trophic specialization using maternal mRNA abundance of five genes ( , , , and ). These findings indicate that variations in egg size in closely related cichlid species can be linked to differences in maternal RNA deposition of key growth-related genes. In addition, the cichlid species with contrasting trophic specialization deposit different levels of maternal mRNAs in their eggs for particular growth-related genes; however, it is unclear whether such differences contribute to differential morphogenesis at later stages of development. Our results provide first insights into this aspect of gene activation, as a basis for future studies targeting their role during ecomorphological specialization and adaptive radiation.