Stress tolerance in diapausing embryos of Artemia franciscana is dependent on heat shock factor 1 (Hsf1)

Abstract

Embryos of the crustacean, Artemia franciscana, may undergo oviparous development, forming encysted embryos (cysts) that are released from females and enter diapause, a state of suppressed metabolism and greatly enhanced stress tolerance. Diapause-destined embryos of A. franciscana synthesize three small heat shock proteins (sHsps), p26, ArHsp21 and ArHsp22, as well as artemin, a ferritin homologue, all lacking in embryos that develop directly into nauplii. Of these diapause-specific molecular chaperones, p26 and artemin are important contributors to the extraordinary stress tolerance of A. franciscana cysts, but how their synthesis is regulated is unknown. To address this issue, a cDNA for heat shock factor 1 (Hsf1), shown to encode a protein similar to Hsf1 from other organisms, was cloned from A. franciscana. Hsf1 was knocked down by RNA interference (RNAi) in nauplii and cysts of A. franciscana. Nauplii lacking Hsf1 died prematurely upon release from females, showing that this transcription factor is essential to the survival of nauplii. Diapause cysts with diminished amounts of Hsf1 were significantly less stress tolerant than cysts containing normal levels of Hsf1. Moreover, cysts deficient in Hsf1 possessed reduced amounts of p26, ArHsp21, ArHsp22 and artemin, revealing dependence on Hsf1 for expression of their genes and maximum stress tolerance. The results demonstrate an important role for Hsf1, likely in concert with other transcription factors, in the survival and growth of A. franciscana and in the developmentally regulated synthesis of proteins responsible for the stress tolerance of diapausing A. franciscana cysts.

Structural properties and cellular expression of AfrLEA6, a group 6 late embryogenesis abundant protein from embryos of Artemia franciscana

“…During anhydrobiosis, tissue water can decrease to less than 2% (Crowe and Madin 1974), which imposes substantial challenges for defending the functionality of biological structures (Crowe et al 1997;Clegg 1973, 1978). One key strategy for desiccation tolerance in many anhydrobiotes is the accumulation of protective molecules such as late embryogenesis abundant (LEA) proteins, heat-shock proteins, and stabilizing organic solutes (Clegg 2005(Clegg , 2011Crowe et al 1998Crowe et al , 2005Hand et al 2011Hand et al , 2018Tan and MacRae 2018;Tapia and Koshland 2014;Tunnacliffe and Wise 2007). The present study focuses on AfrLEA6, a group 6 LEA protein also referred to as a seed maturation protein (SMP).…”

Copepod Embryonic Dormancy: “An Egg Is Not Just an Egg”

“…There is a need for multi-method approaches where physiological responses are detected by classical and modern technologies and/or methods (see Nilsson, 2017;Amato and Carotenuto, 2018;Tarrant et al, 2019). Dormancy can be induced in some animals by steroid hormones and insulin-like peptides (Tan and MacRae, 2018). Protective substances (low and high molecular weight) that maintain molecular structures, such as the disaccharide trehalose (found in, e.g., tardigrades and brine shrimps) (Hashimoto et al, 2016;Tan and MacRae, 2018), as well as molecules that "sense" the environment, must be present.…”

“…Dormancy can be induced in some animals by steroid hormones and insulin-like peptides (Tan and MacRae, 2018). Protective substances (low and high molecular weight) that maintain molecular structures, such as the disaccharide trehalose (found in, e.g., tardigrades and brine shrimps) (Hashimoto et al, 2016;Tan and MacRae, 2018), as well as molecules that "sense" the environment, must be present. Studies should include stimulation of the production of low-molecular-weight protectives, determined by various omics, using, for example, liquid chromatography-mass spectrometry (LC-MS).…”

Quantitative Proteomics Reveals Remodeling of Protein Repertoire Across Life Phases of Daphnia pulex

“…Diapausing eggs capable of surviving freezing, heating, and desiccation are hypothesized to contain high levels of trehalose, a disaccharide commonly used in crustaceans and insects as freezing and desiccation protectant, thus one might expect upregulation of trehalose synthesis and downregulation of trehalose breakdown proteins in ephippia. One may also expect elevated expression in ephippia of stress‐tolerance related proteins, such as small heat‐shock proteins and proteins involved in antioxidant pathways, such as superoxide dysmutases (SODs), peroxidases, and other glutathione metabolism enzymes, and thioredoxins . Additionally, desiccation resistant mosquito shows upregulation of protein repair enzymes protein‐ l ‐isoaspartate‐( d ‐aspartate) O ‐methyltransferases (PIMTs) during desiccation stress .…”