Transcriptomic Analysis Reveals Insights on Male Infertility in Octopus maya Under Chronic Thermal Stress

Abstract

Octopus maya endemic to the Yucatan Peninsula, Mexico, is an ectotherm organism particularly temperature-sensitive. Studies in O. maya females show that temperatures above 27°C reduce the number of eggs per spawn, fertilization rate and the viability of embryos. High temperatures also reduce the male reproductive performance and success. However, the molecular mechanisms are still unknown. The transcriptomic profiles of testes from thermally stressed (30°C) and not stressed (24°C) adult male octopuses were compared, before and after mating to understand the molecular bases involved in the low reproductive performance at high temperature. The testis paired-end cDNA libraries were sequenced using the Illumina MiSeq platform. Then, the transcriptome was assembled de novo using Trinity software. A total of 53,214,611 high-quality paired reads were used to reconstruct 85,249 transcripts and 77,661 unigenes with an N50 of 889 bp length. Later, 13,154 transcripts were annotated implementing Blastx searches in the UniProt database. Differential expression analysis revealed 1,881 transcripts with significant difference among treatments. Functional annotation and pathway mapping of differential expressed transcripts revealed significant enrichment for biological processes involved in spermatogenesis, gamete generation, germ cell development, spermatid development and differentiation, response to stress, inflammatory response and apoptosis. Remarkably, the transcripts encoding genes such as ZMYND15, KLHL10, TDRD1, TSSK2 and DNAJB13, which are linked to male infertility in other species, were differentially expressed among the treatments. The expression levels of these key genes, involved in sperm motility and spermatogenesis were validated by quantitative real-time PCR. The results suggest that the reduction in male fertility at high temperature can be related to alterations in spermatozoa development and motility.

Oviducal gland transcriptomics of Octopus maya through physiological stages and the negative effects of temperature on fertilization

“…RNA extraction, quantitation, and quality check were performed using the protocol, reagents, and instruments described in López-Galindo et al (2019b) and Juárez et al (2019) , starting with 20–30 mg of every whole gland sample. For each experimental condition (MAT24, FER24, SEN24, and FER-TD), a pooled sample was prepared which consisted of 100 ng of RNA from four different individuals ( n = 4).…”

“…DEGs included in the best-represented GO and KEGG categories and those associated with the regulation of OvG activity ( Di Cosmo, Di Cristo & Paolucci, 2001 ; Iwakoshi-Ukena et al, 2004 ; Di Cristo & Di Cosmo, 2007 ; Minakata et al, 2009 ) were selected for cluster analysis and plotted in heatmaps using R software ( R Development Core Team, 2010 ). The analyses were performed following the scripts and parameters set and statistical significance implemented by Juárez et al (2019) and López-Galindo et al (2019b) .…”

“…This ectothermic species is adapted to a narrow temperature range: reproductive events and embryonic development have an upper thermal limit around 27 °C; below that temperature—and optimally around 24 °C—these processes take place successfully. Therefore, reproductive events occur typically on winter and during upwelling pulses when sea temperatures are cooler on this region ( Juárez et al, 2015 ; Caamal-Monsreal et al, 2016 ; Avila-Poveda et al, 2016 ; Angeles-Gonzalez et al, 2017 ; Sanchez-García et al, 2017 ; Pascual et al, 2019 ; López-Galindo et al, 2019a , 2019b ). However, higher temperatures have been reported in its distribution area in recent years, mainly in summer, which may negatively affect the physiological condition and reproductive success in O. maya males and females ( Juárez et al, 2015 , 2016 ; Angeles-Gonzalez et al, 2017 ; Pascual et al, 2019 ; López-Galindo et al, 2019a , 2019b ).…”

“…Therefore, reproductive events occur typically on winter and during upwelling pulses when sea temperatures are cooler on this region ( Juárez et al, 2015 ; Caamal-Monsreal et al, 2016 ; Avila-Poveda et al, 2016 ; Angeles-Gonzalez et al, 2017 ; Sanchez-García et al, 2017 ; Pascual et al, 2019 ; López-Galindo et al, 2019a , 2019b ). However, higher temperatures have been reported in its distribution area in recent years, mainly in summer, which may negatively affect the physiological condition and reproductive success in O. maya males and females ( Juárez et al, 2015 , 2016 ; Angeles-Gonzalez et al, 2017 ; Pascual et al, 2019 ; López-Galindo et al, 2019a , 2019b ). For instance, gene expression patterns in the testis of thermally stressed O. maya males were associated with physiological deficiencies and low motility of the spermatozoa ( López-Galindo et al, 2019b ).…”

“…However, higher temperatures have been reported in its distribution area in recent years, mainly in summer, which may negatively affect the physiological condition and reproductive success in O. maya males and females ( Juárez et al, 2015 , 2016 ; Angeles-Gonzalez et al, 2017 ; Pascual et al, 2019 ; López-Galindo et al, 2019a , 2019b ). For instance, gene expression patterns in the testis of thermally stressed O. maya males were associated with physiological deficiencies and low motility of the spermatozoa ( López-Galindo et al, 2019b ). In O. maya females, the exposure to temperatures above 27 °C significantly reduced the ova production, yolk amount, fertilization, and egg-laying rates ( Juárez et al, 2015 ).…”