Different Transcriptomic Responses to Thermal Stress in Heat-Tolerant and Heat-Sensitive Pacific Abalones Indicated by Cardiac Performance

Abstract

The Pacific abalone Haliotis discus hannai is one of the most economically important mollusks in China. Even though it has been farmed in southern China for almost 20 years, summer mortality remains the most challengeable problem for Pacific abalone aquaculture recently. Here, we determined the different heat tolerance ability for five selective lines of H. discus hannai by measuring the cardiac performance and Arrhenius breakpoint temperature (ABT). The Red line (RL) and Yangxia line (YL) were determined as the most heat-sensitive and most heat-tolerant line, respectively. Heart rates for RL were significantly lower than those of the YL at the same temperature (p < 0.05). The differentially expressed genes (DEGs), which were enriched in several pathways including cardiac muscle contraction, glutathione metabolism and oxidative phosphorylation, were identified between RL and YL at control temperature (20°C) and heat stress temperature (28.5°C, the ABT of the RL) by RNA-seq method. In the RL, 3370 DEGs were identified between the control and the heat-stress temperature, while only 1351 DEGs were identified in YL between these two temperature tests. Most of these DEGs were enriched in the pathways such as protein processing in endoplasmic reticulum, nucleotide binding and oligomerization domain (NOD) like receptor signaling, and ubiquitin mediated proteolysis. Notably, the most heat-tolerant line YL used an effective heat-protection strategy based on moderate transcriptional changes and regulation on the expression of key genes.

Sex differences in early transcriptomic responses to oxidative stress in the copepod Tigriopus californicus

“…Our finding of a greater number of stress DEGs in the less tolerant type (male copepods) is similar to those found in a number of other systems including corals [ 57 ], snails [ 58 ] and abalones [ 59 ]. Importantly we cannot say whether the lower number of stress DEGs in females, by itself, indicates that females have a more efficient response, or simply experienced a lower level of stress.…”

Expression of Heat Shock Proteins in Thermally Challenged Pacific Abalone Haliotis discus hannai

“…Interestingly, the broadcast-spawning physiological nature of abalone facilitates the molecular switch between two states; i.e., aerobiosis and anaerobiosis to perform the basic cellular functions at various thermal conditions [3,5]. This was demonstrated by the positive correlation between temperature and oxygen solubility, and the negative correlation between oxygen solubility and metabolic rate observed in abalone under thermal stress [3,13]. Generally, the growth and reproduction of abalone also differed under thermal and cold temperatures in comparison to optimal-temperature (20 • C) conditions.…”

“…A similar approach was deployed in Haliotis fulgens to explore acute hypoxia and hypercapnia under thermal-stress conditions using a de novo transcriptome, and a co-expression network was constructed among the targeted genes [18]. Previously in Pacific abalone, the gene expression of HSP70 and HSP40 was reported to vary among thermal-sensitive and thermal-tolerant abalones, and the thermal-tolerant line showed higher expression levels than the thermal-sensitive lines [13]. In Haliotis diversicolor, HSP70 was highly expressed in hemocytes under both thermal and pathogen stress due to activation of the immune response [32,33].…”

“…Notably, HSP expression in hemocytes was reproducible, as most of the candidates selected for qRT-PCR analysis showed similar expression patterns in both experiments (Figure 7 and Supplementary Figure S4). Furthermore, in Pacific abalone, 55% of the body is composed of hemolymph, suggesting that hemocytes may function as a standard tissue to assess stress status in comparison to other tissues [13].…”

“…To mitigate temperature-related problems, in-depth knowledge of abalone genetics is required. In particular, for H. discus hannai, few de novo transcriptome profiling studies have been conducted to capture transcript expression patterns under various stresses [12][13][14] since the release of the draft genome [15]. In most studies of Pacific abalone and other abalones, heat shock family proteins were randomly selected as molecular quantification markers for thermally challenged abalones [16][17][18].…”