Abstract
Pyropia haitanensis, a high-yield commercial seaweed in China, is currently undergoing increasing levels of high-temperature stress due to gradual global warming. The mechanisms of plant responses to high temperature stress vary with not only plant type but also the degree and duration of high temperature. To understand the mechanism underlying thermal tolerance in P. haitanensis, gene expression and regulation in response to short- and long-term temperature stresses (SHS and LHS) was investigated by performing genome-wide high-throughput transcriptomic sequencing for a high temperature tolerant strain (HTT). A total of 14,164 differential expression genes were identified to be high temperature-responsive in at least one time point by high-temperature treatment, representing 41.10% of the total number of unigenes. The present data indicated a decrease in the photosynthetic and energy metabolic rates in HTT to reduce unnecessary energy consumption, which in turn facilitated in the rapid establishment of acclimatory homeostasis in its transcriptome during SHS. On the other hand, an increase in energy consumption and antioxidant substance activity was observed with LHS, which apparently facilitates in the development of resistance against severe oxidative stress. Meanwhile, ubiquitin-mediated proteolysis, brassinosteroids, and heat shock proteins also play a vital role in HTT. The effects of SHS and LHS on the mechanism of HTT to resist heat stress were relatively different. The findings may facilitate further studies on gene discovery and the molecular mechanisms underlying high-temperature tolerance in P. haitanensis, as well as allow improvement of breeding schemes for high temperature-tolerant macroalgae that can resist global warming.
Highlights
Pyropia/Porphyra (Bangiales, Rhodophyta) is one of the most economically important mariculture crops
A total of 16 RNA samples generated from two biological replicates of P. haitanensis subjected to eight heat stress treatments were subjected to RNA-Seq
The number (804) of differentially expressed genes (DEGs) between 12 h and 0 h was the lowest, which indicated gene expression levels at 12 h of high temperature stress was close to that at normal condition (0 h), as suggested by a series of short-time physiological regulation responses to short-term high temperature stress (SHS). Over time, these gradually reached the high temperature tolerance point of P. haitanensis, which in turn activated long-time physiological regulation responses to SHS. These results suggest that several early high temperature-responsive genes such as DEGs annotated by energy metabolism-related proteins, antioxidant defense system-related proteins, heat shock proteins (HSPs), signal transduction factors were turned off during the 12 h exposure to high temperature stress and turned on again in response to long-term high temperature stress (LHS) after 12 h (S3 and S4 Files)
Summary
Pyropia/Porphyra (Bangiales, Rhodophyta) is one of the most economically important mariculture crops. Its annual harvest was more than 1,806,000 tons (fresh weight) in 2014 [1]. Pyropia aquaculture has become one of the biggest artificial marine ecological experiments. Transcriptomic study identifies genes involved in thermal adaptation of P. haitanensis. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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