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Growth heterosis in larvae of the Pacific oyster as revealed by MPSS

ABSTRACT: Compared to understanding of biological shape and form, knowledge is sparse regarding what regulates growth and body size of a species. For example, the genetic and physiological causes of heterosis (hybrid vigor) have remained elusive for nearly a century. Here we investigate gene-expression patterns underlying growth heterosis in the Pacific oyster (Crassostrea gigas) in two partially inbred (f=0.375) and two hybrid larval populations produced by a reciprocal cross between the two inbred families. We cloned cDNA and generated 8.6 million sequence tags with massively parallel signature sequencing (MPSSâ). The sequences contain 23,277 distinct signatures that are expressed at statistically non-zero levels and show a highly positively skewed distribution with median and modal counts of 9.25 and 3 transcripts per million, respectively. Approximately 9100 nuclear transcripts are found in all four larval populations, in agreement with the number of genes expressed in sea urchin embryo. For half of the 23,277 signatures, expression level depends on genotype and is predominantly non-additive (hybrids deviate from the inbred average). Statistical contrasts suggest ~350 candidate heterosis genes that exhibit concordant non-additive expression in reciprocal hybrids. Patterns of gene expression, which include dominance for low expression and even underdominance of expression, are more complex than predicted from classical dominant or overdominant explanations of heterosis. Preliminary identification of ribosomal proteins among candidate genes supports the suggestion from previous studies that efficiency of protein metabolism plays a role in heterosis. Keywords: MPSS heterosis larvae expression profiling

ORGANISM(S): Magallana gigas

PROVIDER: GSE3596 | GEO | 2006/11/10

SECONDARY ACCESSION(S): PRJNA93697

REPOSITORIES: GEO

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Project description:Heterosis, a phenomenon where hybrids exhibit superior performance in various traits such as yield, quality, and resistance compared to their parents, has long been a focus of agricultural research. Although tobacco biomass significantly affects tobacco yield and economic profitability, the underlying reasons for the dominance of tobacco biomass hybrids and their formation remain unclear. To address this, we selected 5 tobacco varieties (lines) with large differences in tobacco biomass as the parents and formulated F1 hybrids to analyze the expression of tobacco biomass heterosis. Our findings demonstrate that tobacco leaf biomass exhibits a clear heterosis advantage. In particular, the hybrid Va116×GDH94 showed strong heterosis, with 76.69% of differentially expressed genes (DEGs) displaying Overdominant expression pattern. Notably, these Overdominant DEGs were significantly enriched in biological processes such as photosynthesis and respiration. During photosynthesis, transgressive up-regulation of Lhc improved light-harvesting efficiency, while the up-regulation of Psa and Psb in the photosystem enhanced the defense of chloroplasts against strong light. Additionally, the up-regulation of rbcl promoted the increase of photosynthetic products in the hybrids. During respiration, the down-regulation of MDH, ACO, and OGDH suppressed the tricarboxylic acid cycle (TCA cycle) and weakened respiratory consumption in the hybrids. Furthermore, we observed that the net photosynthetic rate and intercellular CO2 concentration of the hybrids were significantly higher than those of the parents. Taken together, our results suggest that the overdominant expression effect of DEGs plays a crucial role in the formation of tobacco biomass hybrid advantage. The overdominant expression effect of photosynthesis and respiration-related genes enhanced the photosynthetic capacity of the hybrids, reduced respiration consumption, and promoted the increase of tobacco biomass, thus demonstrating the obvious hybrid advantage.

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Growth heterosis in larvae of the Pacific oyster as revealed by MPSS

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